s - Latin American Journal of Aquatic Research

Transcription

Latin American Journal of Aquatic Research
formerly Investigaciones Marinas
ISSN 0718 -560X
www.lajar.cl
www.scielo.cl
CHIEF EDITOR
Sergio Palma
Pontificia Universidad Católica de Valparaíso, Chile
[email protected]
ASSOCIATE EDITORS
Patricio Arana
[email protected]
José Angel Alvarez Perez
Universidade do Vale do Itajaí, Brasil
[email protected]
Walter Helbling
Estación de Fotobiología Playa Unión, Argentina
[email protected]
Nelson Silva
[email protected]
EDITORIAL COMMITTEE
Dagoberto Arcos
Universidad Católica de la Santísima Concepción, Chile
[email protected]
Patricio Bernal
Comisión Oceanográfica Intergubernamental, Francia
[email protected]
Juan Carlos Castilla
Pontificia Universidad Católica de Chile
[email protected]
Jorge Csirke
Departamento de Pesca, FAO, Italia
[email protected]
Fernando L. Diehl
Asociación Brasilera de Oceanografía, Brasil
[email protected]
Pierre Freón
Institut de Recherche pour le Developpement, Francia
[email protected]
Michel Hendrickx
Universidad Nacional Autónoma de México
[email protected]
Víctor Marín
Universidad de Chile
[email protected]
Carlos Moreno
Universidad Austral de Chile
[email protected]
Germán Pequeño
Universidad Austral de Chile
[email protected]
Oscar Pizarro
Universidad de Concepción, Chile
[email protected]
Ricardo Prego
Instituto de Investigaciones Marinas (CSIC), España
[email protected]
Ingo Wehrtmann
Universidad de Costa Rica
[email protected]
Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso
Casilla 1020, Valparaíso, Chile – Fax: (56-32) 2274206, E-mail: [email protected]
LATIN AMERICAN JOURNAL OF AQUATIC RESEARCH
Lat. Am. J. Aquat. Res., 37(3) 2009
CONTENTS
Patricio Arana, José Angel Alvarez Perez & Paulo Ricardo Pezzuto
Deep-sea fisheries off Latin America: an introduction………………………..……………..……………………………. 281-284
Research Articles
Mauricio Ahumada & Patricio Arana
Pesca artesanal de cangrejo dorado (Chaceon chilensis) en el archipiélago de Juan Fernández, Chile. Artisanal fishing
for golden crab (Chaceon chilensis) off the Juan Fernández archipelago, Chile…………………………...…..…………….. 285-296
Paulo Ricardo Pezzuto & Rodrigo Sant’Ana
Sexual maturity of the deep-sea royal crab Chaceon ramosae Manning, Tavares & Albuquerque, 1989 (Brachyura:
Geryonidae) in southern Brazil. Madurez sexual del cangrejo real Chaceon ramosae Manning, Tavares & Albuquerque, 1989
(Brachyura: Geryonidae) en el sur de Brasil………………………………………………………………….………………….. 297-312
Cristian Canales & Patricio Arana
Crecimiento, mortalidad y evaluación de la población de cangrejo dorado (Chaceon chilensis) explotado en el archipiélago de Juan Fernández, Chile. Growth, mortality, and stock assessment of the golden crab (Chaceon chilensis) population exploited in the Juan Fernández archipelago, Chile……………………………………………………………….……...... 313-326
Rodrigo Dallagnolo; José Angel Alvarez Perez; Paulo Ricardo Pezzuto & Roberto Wahrlich
The deep-sea shrimp fishery off Brazil (Decapoda: Aristeidae): development and present status. La pesquería de gambas de profundidad en Brasil (Decapoda: Aristeidae): desarrollo y estado actual…………………………………….……… 327-346
Aurora Guerrero & Patricio Arana
Size structure and sexual maturity of the golden crab (Chaceon chilensis) exploited off Robinson Crusoe Island, Chile.
Estructuras de tallas y madurez en el cangrejo dorado (Chaceon chilensis) explotado alrededor de la isla Robinson Crusoe,
Chile…………………………………………………………………………………………………………………………….….….. 347-360
Fishing yields and size structures of Patagonian toothfish (Dissostichus eleginoides) caught with pots and long-lines
off far southern Chile. Rendimientos de pesca y estructuras de tallas de bacalao de profundidad (Dissostichus eleginoides)
capturados con trampas y espineles en el extremo sur de Chile…………………………………………………………. 361-370
Edward Barriga, Carlos Salazar, Jacqueline Palacios, Miguel Romero & Aldo Rodríguez
Distribución, abundancia y estructura poblacional del langostino rojo de profundidad Haliporoides diomedeae (Crustacea: Decapoda: Solenoceridae) frente a la zona norte de Perú (2007-2008). Distribution, abundance, and population
structure of deep red shrimp Haliporoides diomedeae (Crustacea: Decapoda: Solenoceridae) off northern Perú (20072008)………………..……………………………………………………………………………………………………...………….. 371-380
Patricio Arana
Reproductive aspects of the Patagonian toothfish (Dissostichus eleginoides) off southern Chile. Aspectos reproductivos
del bacalao de profundidad (Dissostichus eleginoides), en el extremo austral de Chile. ………………………………… 381-394
Manuel Haimovici, Luciano Gomes Fischer, Carmem L.D.B.S. Rossi-Wongtschowski, Roberto Ávila Bernardes & Roberta
Aguiar dos Santos
Biomass and fishing potential yield of demersal resources from the outer shelf and upper slope of southern Brazil.
Biomasa y rendimiento potencial de recursos demersales de la plataforma externa y talud superior del sur de Brasil… 395-408
José Angel Alvarez Perez, Tiago Nascimento Silva, Rafael Schroeder, Richard Schwarz & Rodrigo Silvestre Martins
Biological patterns of the Argentine shortfin squid Illex argentinus in the slope trawl fishery off Brazil. Patrones biológicos del calamar argentino Illex argentinus en la pesquería de arrastre en el talud continental de Brasil………………. 409-428
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Rodrigo Sant’Ana & Paulo Ricardo Pezzuto
Sexual maturity of the deep-sea red crab Chaceon notialis Manning & Holthuis, 1989 (Brachyura: Geryonidae) in southern Brazil. Madurez sexual del cangrejo rojo de profundidad Chaceon notialis Manning & Holthuis, 1989 (Brachyura: Geryonidae) al sur de Brasil…………………………………………………………………………………………………….....……..... 429-442
Paulo Ricardo Pezzuto & Martin Coachman Dias
Reproductive cycle and population structure of the deep-water shrimp Aristeus antillensis A. Milne Edwards & Bouvier, 1909 (Decapoda: Aristeidae) on southeast Brazilian continental slope. Ciclo reproductivo y estructura poblacional del
camarón de aguas profundas Aristeus antillensis A. Milne Edwards & Bouvier, 1909 (Decapoda: Aristeidae) en el talud continental del sureste de Brasil………………………………………………………………………………………………………..... 443-454
Jacqueline Palacios, Edward Barriga, Carlos Salazar, Aldo Rodríguez & Miguel Romero
Aspectos de la biología de Coryphaenoides delsolari Chirichigno & Iwamoto, 1977 frente a la zona norte del Perú. Aspects of the biology of Coryphaenoides delsolari Chirichigno & Iwamoto, 1977 off northern Perú………………...……….. 455-462
Rendimientos, estructuras de tallas y madurez sexual del alfonsino (Beryx splendens) capturado en el cordón submarino de Juan Fernández, Chile. Fishing yields, size structures, and sexual maturity of alfonsino (Beryx splendens) caught on
Juan Fernandez seamounts, Chile…………………………………………………………………………..……………….……. 463-478
Reviews
Mauricio Gálvez-Larach
Montes submarinos de Nazca y Salas y Gómez: una revisión para el manejo y conservación. Seamounts of Nazca and
Salas y Gómez: a review for management and conservation purposes…………………………………….…………………. 479-500
Malcolm R. Clark
Deep-sea seamount fisheries: a review of global status and future prospects. Pesquerías de aguas profundas realizadas
en montes submarinos: revisión global de su estado y perspectivas futuras……………………………………………… 501-512
José Angel Alvarez Perez, Paulo Ricardo Pezzuto, Roberto Wahrlich & Ana Luisa de Souza Soares
Deep-water fisheries in Brazil: history, status and perspectives. Pesquerías de aguas profundas en Brasil: historia, situación actual y perspectivas…………………………………………………………………………………………………………… 513-542
Ingo S. Wehrtmann & Vanessa Nielsen-Muñoz
The deepwater fishery along the Pacific coast of Costa Rica, Central America. Pesca en aguas profundas a lo largo de la
costa Pacífica de Costa Rica, América Central................................................................................................................... 543-554
Eleuterio Yáñez, Claudio Silva, Rodrigo Vega, Fernando Espíndola, Lorena Álvarez, Nelson Silva, Sergio Palma, Sergio Salinas, Eduardo Menschel, Verena Häussermann, Daniela Soto & Nadín Ramírez
Seamounts in the southeastern Pacific Ocean and biodiversity on Juan Fernandez seamounts, Chile. Montes submarinos en el océano Pacífico suroriental y biodiversidad en el cordón submarino de Juan Fernández, Chile………………. 555-570
Short Communications
Tiago Barros Carvalho, Ronaldo Ruy de Oliveira Filho & Tito Monteiro da Cruz Lotufo
Note on the fisheries and biology of the golden crab (Chaceon fenneri) off the northern coast of Brazil. Nota sobre la
biología y la pesca del cangrejo dorado (Chaceon fenneri) frente a la costa norte de Brasil…………………………… 571-576
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Lat. Am. J. Aquat. Res., 37(3): 281-284, 2009 Deep-sea fisheries off Latin America: an introduction
“Deep-sea fisheries off Latin America”
P. Arana, J.A.A. Perez & P.R. Pezzuto (eds.)
DOI: 10.3856/vol37-issue3-fulltext-1
281
Deep-sea fisheries off Latin America: an introduction
Patricio Arana1, José Angel Alvarez Perez2 & Paulo Ricardo Pezzuto2
P.O. Box 1020, Valparaíso, Chile
2
Centro de Ciências Tecnológicas da Terra e do Mar, Universidade do Vale do Itajaí
Rua Uruguai 458, Centro, Itajaí, SC, Brazil
1
Recent assessments of the state of the world’s marine
capture fisheries demonstrate that global catches have
attained (or surpassed) maximum sustainable levels in
the last two decades (Pauly et al., 2002). These reports
also point out three critically related global trends: (a)
fishing efforts in developing countries have increased
in order to meet the high demands of the “overfished”
developed world (Garcia & Grainger, 2005; Pauly et
al., 2005), (b) catches have concentrated on smaller
organisms of lower trophic levels (Pauly et al., 1998),
and (c) fishing has gone deeper (Morato et al., 2006). It
has been argued that developing coastal countries,
concentrated in the Southern Hemisphere, have developed their offshore fishing capacity (through national
fleet enhancement or foreign fishing agreements) in
order to further production of both large, high-value
and small, low-value fish (and shellfish); the former
are destined for international markets and the latter to
supply domestic food demands. Worldwide, this process has also been associated with the progressive occupation of deeper areas by commercial fleets, initially in
search of better catches of shelf targets but eventually
aiming at the exploitation of some highly profitable,
typically deep-water species (Japp & Wilkinson,
2007).
Largely embedded in the developing world, Latin
America may be seen as a good example of such
trends. It comprises 20 coastal countries whose Economic Exclusive Zones (EEZs) extend into the southwestern Atlantic, eastern Pacific, Southern Oceans, and
Caribbean Sea. The region has historically contributed
over 15% the world’s marine fish production, although
most of this has concentrated on fishmeal produced by
massive catches of small pelagic fish in upwelling
zones off Peru and Chile. In recent decades, however,
Latin American fisheries production not only increased
continuously but also diversified, shifting its focus to
the production of fish for human con-sumption (as
opposed to fishmeal) and trading with the USA, EU,
and Japan (Wiefels, 2003). As the new millennium
progressed, Latin America became a major net export
region reporting, in 2006, an 8 billion US$ surplus in
fish and the fish products trade (Garcia & Grainger,
2005; FAO, 2009). Notwithstanding, several large
Latin American countries have also experienced a
growing domestic demand for seafood, and regional
fishery development seems to have been motivated by
obtaining hard currency rather than food security
(Wiefels, 2003). In the context of said fishing development history, it stands to be asked: has fishing also
gone deeper off Latin American countries?
Deep-water fishing, normally defined as fishing
conducted near the seafloor beyond the continental
shelf break (including slope areas, seamounts, and
seamount ridges), emerged in the 1950s through pioneer operations of Russian trawlers on the northern
mid-Atlantic ridge (Troyanovsky & Lisovsky, 1995;
Japp & Wilkinson, 2007). In the following decades
(1960-2000), fishing technologies advanced and deepwater fisheries expanded to all oceanic regions of the
world, being particularly important in northern temperate-water oceans (i.e. Northeast Atlantic) (Sissewine &
Mace, 2007). In 2004, over 5.6 million tonnes of deepwater species were reported worldwide; of these, 2.4
million (43%) were blue ling (Molva dypterygia)
catches obtained in the northeastern Atlantic along
with other species, including Greenland halibut
(Reinhardtius hippoglossoides), ling (Molva molva),
northern prawn (Pandalus borealis), roundnose grenadier (Coryphaenoides rupestris), and others. The
southeastern Pacific and southwestern Atlantic, where
most Latin American countries fish, contributed no
more than 3% of global deepwater catches in 2004.
Nevertheless, over 350,000 tonnes of total catches
were reported that year of Patagonian toothfish (Dissostichus eleginoides), Patagonian grenadier (Macruronus magellanicus), the pink cusk-eel (Genypterus
blacodes), and southern blue whiting (Micromesistius
282
Lat. Am. J. Aquat. Res.
australis) (Sissewine & Mace, 2007), all resources
from temperate waters. Notwithstanding these official
figures, considerable deepwater fishing activity has
been reported off Latin America, particularly at lower
latitudes and in tropical waters such as the Brazil slope
area (Perez et al., 2003), the Nazca Ridge (Parin et al.,
1997), and seamounts in the southeast Pacific Ocean
and off the coast of Chile (Arana, 2003). Despite the
lack of comprehensive and widely accessible information, these reports suggested that the Latin American
fishery was also going deep.
These were the feelings that motivated the Latin
American
Association
of
Marine
Sciences
(ALICMAR) to promote the first workshop fully focused on compiling comprehensive studies on deep-sea
fisheries off Latin American countries in 2007 during
the XII COLACMAR (Latin American Congress of
Marine Science) held in Florianópolis, Brazil. During
the event, nine oral presentations by researchers from
New Zealand, Spain, Costa Rica, Brazil, Chile, and
Uruguay offered a rich overview on the biology and
fisheries of deepwater resources in Latin America, the
eastern Atlantic, and seamounts around the world. A
consensus emerged from the workshop participants
that a thorough, perennial recording of this otherwise
quite dispersed knowledge should be attempted in
order to fully document and recognize Latin American
deep-water fisheries, biology, and management.
A contemporary agreement celebrated between the
Pontificia Universidad Católica de Valparaíso (Chile)
and Universidade do Vale do Itajaí (Brazil) during the
XII COLACMAR produced the appropriate collaborative environment to envisage a joint edition of a volume of the Latin American Journal of Aquatic Research (LAJAR) especially devoted to the publication
of invited and fully peer-reviewed papers on Latin
American deep-sea fisheries and resources. Editorial
Table 1. Main deep-water species dealt with in the papers published in this issue, by region and fishery status.
Tabla 1. Principales especies que son tratadas en el presente número de la revista, por región y situación pesquera de cada
una de ellas.
Region
Resources
Fish
Alfonsino
Granadero
Patagonian toothfish
Orange roughy
Tylefish
Monkfish
Argentine hake
Wreckfish
Brazilian codling
Silver John dory
Beryx splendens
Coryphaenoides delsolari
Dissostichus eleginoides
Hoplostethus atlanticus
Lopholatillus villarii
Lophyus gastrophysus
Merluccius hubbsi
Polyprion americanus
Urophycis mystacea
Zenopsis conchifera
Crustaceans
Giand red shrimp
Scarlet shrimp
Alistado shrimp
Golden crab
Golden crab
Red crab
Royal crab
Red royal shrimp
Camellón shirmp
Camellito shrimp
Fidel shrimp
Aristaeomorpha foliacea
Aristaeopsis edwardsiana
Aristeus antillensis
Chaceon chilensis
Chaceon fenneri
Chaceon notialis
Chaceon ramosae
Haliporoides diomedeae
Heterocarpus affinis
Heterocarpus vicarius
Solenocera agassizii
Molluscs
Argentine shortfin squid
Illex argentinus
Atlantic
ocean
Pacific
ocean
Status
Seamounts
elsewhere
Potential
resource
Developing
fishery
Exploited/
overexploited
Deep-sea fisheries off Latin America: an introduction
efforts directed at contacting and enlisting/enrolling/recruiting as many contributors as possible
from all regional countries resulted in a total of 20
articles that compile information on deep-water fisheries carried out between 2000 and 2008 off both the
Pacific (11) and Atlantic (8) coasts of Latin America.
The majority of the data presented originated from
slope areas and seamounts within the EEZs of Brazil
(8), Chile (7), Perú (2), and Costa Rica (1) as well as
the high-seas (2). The studies span a variety of aspects
of deep-sea fisheries including: (a) regional fishing
development, (b) stock assessments and biological
studies, (c) fishing management, and (d) biodiversity
and conservation of deep Vulnerable Marine Ecosystems.
Detailed information about 22 potential, developing, and exploited/overexploited deep-sea resources
has been made available by these papers, most of
which (12) focus on shellfish stocks including several
shrimps, four geryonid crabs, and one squid (Table 1).
This fact adds particular interest to this volume: unlike
other areas of the World Ocean where deep-sea fisheries have been demonstrated to concentrate largely on
bony and cartilaginous fishes (see reviews in FAO,
2007), benthic and demersal invertebrates are comparatively more important in Latin American fisheries.
Not surprisingly, concerns about the sustainability
of these fragile deep-water resources and their respective habitats have also emerged as a recurrent topic in
this volume, as 45% of the reported species have already been revealed to be exploited or overexploited in
the region despite their relatively recent fishing history
(Table 1). Therefore, as the international community
mobilizes research and diplomatic efforts to limit and
regulate the economic exploitation of deep-sea environments in EEZs and on the high-seas by designing
general agreements and recommendations (FAO, 2007)
or establishing regional fishing management organizations (i.e. South Pacific Regional Fishing Management
Organization; www.south pacificrfmo.org), this volume is intended to contribute the necessary knowledge
to promote the sustainable management of Latin
American deep-water environments and their respective resources.
REFERENCES
Arana, P. 2003. Experiencia chilena en faenas de pesca en
aguas profundas y distantes: Evolución y perspectivas.
In: E. Yáñez (ed.). Actividad pesquera y de acuicultura en Chile. Escuela de Ciencias del Mar, PUCV, pp.
57-79.
Food and Agriculture Organization (FAO). 2007. Report
and documentation of the expert consultation on deep-
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sea fisheries in the high seas. Bangkok, Thailand, 2123 November 2006. FAO Fish. Rep., 838: 208 pp.
Food and Agriculture Organization (FAO). 2009. The
state of the world fisheries and aquaculture 2008.
FAO, Rome, 196 pp.
Garcia, S.M. & R.J.R. Grainger. 2005. Gloom and doom?
The future of marine capture fisheries. Phil. Trans. R.
Soc., B 360: 21-46.
Japp, D.W. & S. Wilkinson. 2007. Deep-sea resources
and fisheries. In: Report and documentation of the expert consultation on deep-sea fisheries in the high
seas. Bangkok, Thailand, 21-23 November 2006. FAO
Fish. Rep., 838: 39-59.
Morato,T., R. Watson, T.J. Pitcher & D. Pauly. 2006.
Fishing down the deep. Fish & Fisheries, 7: 24-34.
Parin, N.V., A.N. Mironov & K.N. Nesis. 1997. Biology
of the Nazca and Sala y Gómez submarine ridges, an
outpost of the Indo-West Pacific fauna in the Eastern
Pacific Ocean: composition and distribution of the
fauna, its communities and history. In: A.V. Gebruk,
E.C. Southward & P.A. Tyler (eds.). The biogeography of the oceans. Adv. Mar. Biol., 32: 145-242.
Pauly, D., V. Christensen, J. Dalsgaard, R. Froese & F.C.
Torres, Jr. 1998. Fishing down marine food webs. Science, 279: 860-863.
Pauly, D., V. Christensen, S. Guénette, T.J. Pitcher, U.R.
Sumaila, C.J. Walters, R. Watson & D. Zeller. 2002.
Towards sustainability in world fisheries. Nature, 418:
689-695.
Pauly, D., R. Watson & J. Alder. 2005. Global trends in
world fisheries: impacts on marine ecosystems and
food security. Phil. Trans. R. Soc., B 360: 5-12.
Perez, J.A.A., R. Wahrlich, P.R. Pezzuto, P.R. Schwingel,
F.R.A. Lopes & M. Rodrigues-Ribeiro. 2003. Deepsea fishery off southern Brazil: recent trends of the
Brazilian fishing industry. J. Northw. Atl. Fish. Sci.,
31: 1-18.
Sissewine, M.P. & P. Mace. 2007. Can deep water fisheries be managed sustainably? In: Report and documentation of the expert consultation on deep-sea fisheries
in the high seas. Bangkok, Thailand, 21-23 November
2006. FAO Fish. Rep., 838: 61-112.
Troyanovsky, F.M. & S.F. Lisovsky. 1995. Russian
(USSR) fisheries research in deep-waters (below 500
m) in the north Atlantic. In: A.G. Hooper (ed.) Deepwater fisheries of the north Atlantic oceanic slope.
Kluwer Academic Publishers, Netherlands, pp. 357365.
Wiefels, R. 2003. Study on the impact of international
trade in fishery products on food security in Latin
America – A regional approach. In: Report of the expert consultation on international fish trade and food
security. Casablanca, Morocco, 27-30 January 2003.
FAO Fish. Rep., 708: 155-161.
284
Lat. Am. J. Aquat. Res., 37(3): 285-296,Pesca
2009 de Chaceon chilensis en el archipiélago de Juan Fernández
285
Research Article
Pesca artesanal de cangrejo dorado (Chaceon chilensis) en el archipiélago de Juan
Fernández, Chile
1
Mauricio Ahumada1 & Patricio Arana1
RESUMEN. Se describe la pesca artesanal de cangrejo dorado (Chaceon chilensis) en las islas Robinson Crusoe y Santa Clara, en el archipiélago de Juan Fernández (Chile), desarrollada entre julio de 2005 y mayo de
2006. Se dan a conocer aspectos biológico-pesqueros relativos a esfuerzo y rendimientos de pesca, proporción
sexual, así como los resultados de una evaluación directa de biomasa vulnerable mediante el método de área
de influencia de las trampas. La extracción se efectuó fundamentalmente en el cuadrante NE de ambas islas,
mediante botes de madera de 9,0 m de eslora. Se monitorearon 157 salidas de pesca y se capturaron 13.903
ejemplares, los cuales mayoritariamente fueron machos (97,5%). La CPUE promedio fue 16,7 ejemplares por
trampa y de 13,5 ejemplares comerciales por trampa. A partir del muestreo sistemático, se detectó al recurso
entre 300 y 1000 m de profundidad, con mayores rendimientos entre 400 y 500 m de profundidad (19,8 y 15,9
ejemplares por trampa). Se consideran y discuten dos escenarios de evaluación de stock para ejemplares de talla comercial en el área actualmente explotada (45,8 km2), el primero estimó un radio efectivo para las trampas
de 13,4 m (área de 564,1 m2), con una biomasa vulnerable de 1.002 ton, equivalentes a 832.983 ejemplares,
mientras que el segundo consideró un radio de 30,0 m con una biomasa vulnerable de 203 ton equivalente a
168.587 ejemplares.
Palabras clave: pesca artesanal, Chaceon chilensis, cangrejo dorado, aguas profundas, archipiélago de Juan
Fernández, Chile.
Artisanal fishing for golden crab (Chaceon chilensis) off the Juan Fernández
archipelago, Chile
ABSTRACT. This work describes the artisanal golden crab (Chaceon chilensis) fishery off Robinson Crusoe
and Santa Clara islands in the Juan Fernández archipelago (Chile) developed between July 2005 and May
2006. We report biological fishery aspects related to the fishing efforts and yields, the sexual proportion of the
catch, and the results of a direct evaluation of the vulnerable biomass done using the trap area of influence
method. The extraction was done mainly in the NE quadrant of both islands from wooden boats (9.0 m
length). Monitoring was done during 157 fishing trips, in which 13,903 specimens were caught; most were
males (97.5%). The average CPUEs were 16.7 specimens per trap and 13.5 commercial specimens per trap.
Systematic sampling revealed the resource between 300 and 1000 m depth, with the greatest yields between
400 and 500 m depth (19.8 and 15.9 specimens per trap). Two stock assessment scenarios were considered and
discussed for commercial-sized specimens in the currently exploited area (45.8 km2). The first scenario estimated an effective radius for the traps of 13.4 m (564.1 m2 in area), obtaining a vulnerable biomass of 1002
tons, equivalent to 832,983 specimens. The second scenario considered a radius of 30.0 m, giving a vulnerable
biomass of 203 tons, or 168,587 specimens.
Keywords: artisanal fishery, Chaceon chilensis, golden crab, deep waters, Juan Fernández archipelago, Chile.
________________________
Corresponding author: Patricio Arana ([email protected])
286
INTRODUCCIÓN
El archipiélago de Juan Fernández se localiza aproximadamente a 360 mn frente a la costa continental de
Chile central y comprende a un grupo de tres islas:
Robinson Crusoe, Santa Clara y Alejandro Selkirk.
Debido a la importancia ecológica de su flora y fauna,
dicho territorio fue declarado Parque Nacional en
1935 y Reserva Mundial de la Biosfera en 1977.
Las islas están pobladas por aproximadamente 600
habitantes, quienes han desarrollado tradicionalmente
una actividad económica concentrada en la pesca artesanal de langosta de Juan Fernández (Jasus frontalis),
y en menor medida, algunas especies de peces (Arana
& Toro, 1985). Considerando la necesidad de diversificar las operaciones pesqueras, en 1997 se efectuaron
faenas de pesca exploratoria tendientes a prospectar y
evaluar recursos alternativos, trabajo que a la fecha ha
derivado en la explotación incipiente de cangrejo dorado (Chaceon chilensis), por algunas embarcaciones
del archipiélago (Arana, 2000a; 2000b).
En la actualidad, la pesca de este cangrejo Geryonidae se efectúa exclusivamente por botes artesanales
de madera de pequeño tamaño, a diferencia de otras
especies del mismo género explotadas en el Atlántico
americano, como C. quinquedens (Estados Unidos y
Canadá) (Lawton & Duggan, 1998; Steimle et al.,
2001), C. notialis en Uruguay, C. ramosae y C. notialis en el sudeste de Brasil (Pezzuto et al., 2002; Perez
et al., 2003) y C. fenneri en la costa norte de Brasil
(Carvaho et al., 2009). Así, dada la particularidad de
esta pesquería, como la importancia ecológica de las
islas, este trabajo tuvo por objeto recopilar información operacional de las faenas extractivas y biológicopesquera de Chaceon chilensis, además de estimar su
biomasa vulnerable mediante un método de evaluación directa.
MATERIALES Y MÉTODOS
Se analizó la pesca artesanal de cangrejo dorado (Chaceon chilensis) en aguas circundantes a las islas Robinson Crusoe y Santa Clara, en el archipiélago de
Juan Fernández, Chile (33°39’S-78°51’W) entre julio
de 2005 y mayo de 2006 (Fig. 1). En dicho período, se
caracterizó la captura por unidad de esfuerzo (CPUE)
de la especie objetivo (número de individuos por
trampa), recopilándose además información operativa
de las faenas de pesca.
Las embarcaciones utilizadas en las faenas extractivas correspondieron a botes de madera de doble proa
con eslora y manga típicas de 9,0 y 2,0 m, equipadas
con motores fuera de borda con potencias en torno a
los 20 HP, y viradores verticales u horizontales, además de elementos de propulsión y mando alternativos.
Los aparejos de pesca, correspondieron a trampas con
forma de paralelepípedo recto, construidas de madera
local, similares a las utilizadas en la captura de langosta, pero de mayor tamaño (1,5 m de largo). Su diseño
consta de una entrada, localizada en el panel superior
de la trampa con paredes recubiertas de material plástico, generalmente polietileno (PE) o cloruro de polivinilo (PVC), que facilita que los ejemplares se deslicen al interior, a la vez que obstaculiza su escape.
Las trampas se adosaron a un sistema de señalización compuesto por boyas (generalmente 4 ó 5), mediante un cabo de polipropileno (PP) torcido de 8 mm
de diámetro. Se calaron provistas de lastre y carnada,
consistente en pescado fresco entero o trozado, fijada
libremente al interior de cada aparejo, y dispuestas
individualmente o formando tenas de dos aparejos.
Al respecto, cabe señalar que la extracción de cangrejo dorado es una actividad reciente, en la cual participa un número reducido de embarcaciones, que
efectúan una baja cantidad de lances, motivo por el
cual, el trabajo se planificó bajo un esquema de censo
de viajes de pesca, lances y captura. Se registró en
cada lance el esfuerzo (número de trampas revisadas),
la captura total y comercial (número de ejemplares),
separada por sexo y condición de los ejemplares (machos, hembras y hembras ovíferas), mes, zona de pesca y profundidad, georreferenciándose los principales
caladeros mediante GPS (Magellan Meridian Gold), y
también se registró la fauna acompañante capturada
incidentalmente por los aparejos de pesca.
Se consideró como ejemplares comerciales a los
individuos con un ancho cefalotorácico (AC) de al
menos 130 mm, equivalente a 108 mm LC. La identificación de sexo y condición reproductiva de los
ejemplares se efectuó considerando las diferencias
morfológicas abdominales entre machos y hembras,
además de la presencia o ausencia de huevos.
Adicionalmente, entre el 23 de noviembre de 2005
y el 4 de marzo de 2006, se realizó la evaluación directa de cangrejo dorado mediante el método de área de
influencia del aparejo de pesca (Arena et al., 1994).
Para ello, se utilizaron dos embarcaciones artesanales,
considerando como área de trabajo aquella situada en
el cuadrante nororiente de la isla Robinson Crusoe,
que corresponde al sector explotado actualmente por
los pescadores artesanales.
De esta manera, la abundancia y biomasa vulnerable, en una partición “t”, se calculó en términos de:
⎛ cpuet
⎜
⎜ q
t =1 ⎝
n
∑
⎞
⎟ At
⎟
⎠
: abundancia vulnerable
Pesca de Chaceon chilensis en el archipiélago de Juan Fernández
287
Figura 1. Distribución de los lances de pesca de cangrejo dorado (Chaceon chilensis), entre julio de 2005 y mayo de
2006, alrededor a las islas Robinson Crusoe y Santa Clara.
Figure 1. Distribution of golden crab (Chaceon chilensis) fishery hauls around Robinson Crusoe and Santa Clara islands
between July 2005 and May 2006.
L
∑ ( Abundancial ⋅ wl ) : biomasa vulnerable
l =1
donde, el coeficiente de capturabilidad “q” corresponde al cuociente entre la captura por unidad de esfuerzo
(c/f) y la densidad del stock (D), y la biomasa vulnerable se expresó en función de la abundancia a la talla
“l” (Abundancial) y al l-ésimo peso promedio ( wl ),
según la relación longitud-peso, definida como:
cpuet
q
At
: Captura por trampa promedio en la partición
“t” (unidades trampa-1)
: Coeficiente de capturabilidad del recurso
(km2 trampa-1)
: Área de distribución del recurso, en la partición “t” (km2)
Para efectuar la evaluación directa, se consideró el
enfoque de Aedo & Arancibia (2003). Dichos autores
diferencian entre el área de atracción del aparejo
“Aatr”, correspondiente a la superficie en torno a la
trampa dentro de la cual son atraídos los ejemplares, y
el área efectiva de pesca “Aef”, definida como aquella
en que la probabilidad teórica de captura de los ejemplares es 100%, que equivale al coeficiente de capturabilidad “q”.
El diseño de muestreo fue sistemático y se efectuaron en tres zonas de manera aleatoria al interior del
área de trabajo ya indicada, aproximadamente frente a
los sectores denominados Cerro Alto, Bahía Cumberland y Puerto Francés, entre los veriles de 300 y 1000
m. Se planificaron ocho estaciones de muestreo, separadas entre sí por intervalos de 100 m de profundidad,
las cuales fueron localizadas mediante la utilización de
GPS y un ecosonda modelo Raythoon V8010 instalado a bordo de la embarcación.
El diseño de muestreo contempló el calado de seis
trampas por estación, correspondientes a aparejos
empleados habitualmente por los pescadores en sus
operaciones de pesca. En dos de las zonas (Cerro Alto
y Bahía Cumberland) se utilizaron trampas individuales por línea de pesca, en tanto que frente a Puerto
Francés, se usaron tenas con dos aparejos de pesca por
línea (con separación de 30 m entre ambas trampas).
La carnada y tiempo de reposo fueron los utilizados
comúnmente por los pescadores de la isla (48 a 72 h),
programándose un total de 48 lances por zona, con
144 lances para la totalidad de la prospección.
288
Para estimar el radio de atracción del aparejo de
pesca se consideró un diseño experimental que empleó
tenas con dos trampas de pesca, las que fueron dispuestas en un caladero de C. chilensis, a una profundidad constante de 400 m, con distintas separaciones
entre trampas, correspondientes a 30, 60, 90 y 120 m.
Así, el área de atracción del aparejo “Aatr” se obtuvo
empleando el método de aproximación numérica
Raphson Newton (Burden & Faires, 2002), considerando la distancia entre trampas caladas “Smax”, correspondiente a aquella en donde la CPUE alcanzó un
valor asintótico, según:
(
cpue s = a 1 − exp −b⋅s
)
: captura media por unidad de
esfuerzo a una distancia “s” de
separación de trampas
⎛S
⎞
Aatr = π ⎜ max ⎟
⎝ 2 ⎠
RESULTADOS
2
: área de atracción de la trampa
Para estimar el área efectiva “Aef”, se empleó un
supuesto de área circular en torno a cada aparejo, considerando que Cp = 1 para una distancia d = 0, y Cp =
0,02 para una distancia “d”, equivalente al radio de
atracción “ratr” (Aedo & Arancibia, 2003), conforme a
la siguiente relación:
C p = m ⋅ exp − n⋅d
: probabilidad de captura teórica
a una distancia “d” de la trampa.
donde m = 1 , que supone que la probabilidad de captura a una distancia cero de la trampa es de 100% y
n = ln(0,02) / ratr , parámetro correspondiente a la
variación relativa de la probabilidad de captura teórica
ante un cambio unitario de la distancia “d”. Conforme
a lo anterior, se estimó el radio efectivo de pesca,
según:
ref =
neal, según rutina numérica de Raphson Newton
(Burden & Faires, 2002), utilizando la minimización
de la suma del error cuadrático.
La biomasa vulnerable se estimó extrapolando la
CPUE promedio, obtenida mediante el diseño sistemático, al área de distribución “At” del recurso objetivo,
considerando el sector delimitado por la posición de
los lances comerciales monitoreados de pesca, el supuesto de un área efectiva circular en torno a la trampa
(Arena et al., 1994) y una talla mínima comercial de
108 mm de LC. Además, se consideró la corrección
del área de influencia de la trampa, en caso de solapamiento de áreas efectivas, según área de segmento
circular.
1 − exp−n⋅ratr
n
: radio efectivo de pesca
Adicionalmente, se consideró un escenario alternativo de evaluación, que consideró los radios de influencia de trampas (30 m), reportados en la evaluación directa de otros gerionídeos, destacando entre
ellos a McElman & Elner (1982), Melville-Smith
(1986) y Defeo et al. (1990).
Para determinar la relación talla (LC)-peso de los
ejemplares capturados, se obtuvo una muestra, pesando y midiendo los individuos en tierra; el peso mediante balanza electrónica (0,1 g de precisión) y la
longitud cefalotorácica (LC) con pie de metro (0,1 mm
de precisión). Para estimar los parámetros, se consideró una relación de poder, empleando un ajuste no li-
Se determinó que ocho embarcaciones fueron utilizadas esporádicamente en la pesca de Chaceon chilensis,
las que combinaron operaciones destinadas a la pesca
de este recurso y de la langosta de Juan Fernández
(Jasus frontalis). Desde el punto de vista operacional,
las mareas fueron diurnas, con duraciones aproximadas de 12 h y una periodicidad media de 2,5 días.
Durante las faenas de pesca, se distinguieron las actividades de captura de carnada, preparación de trampas, localización de caladeros, virado, revisión, calado
de trampas y manipulación de la captura a bordo. La
carnada utilizada correspondió a especies ícticas como
Pseudocaranx chilensis, Seriola lalandi, Gymnotorax
porphyreus, Caprodon sp. y ocasionalmente, pulpo
(Octopus sp.).
Con respecto al esfuerzo de pesca, se monitorearon
157 salidas de pesca, dicho valor correspondió a una
muestra del total, dado que no fue posible recopilar
datos en una de las embarcaciones durante todo el
período de estudio. El número de salidas de pesca
mensual varió entre un mínimo de siete (octubre, febrero y abril) y un máximo de 37 (agosto). El total de
trampas viradas fue 831, mensualmente el número de
aparejos virados estuvo comprendido entre 38 (febrero) y 128 (agosto) (Fig. 2).
El esfuerzo de pesca orientado a C. chilensis se
distribuyó entre julio y marzo en el cuadrante NE de la
isla Robinson Crusoe, frente a los sectores La Vaquería, Bahía Cumberland y Puerto Francés, mientras que
en abril y mayo de 2006, se incorporó el área al sur de
la isla, frente a Bahía Villagra y Playa Larga (Fig. 2).
Batimétricamente, las trampas se calaron entre 300 y
675 m, con un promedio global de 468 m de profundidad, indicador que mensualmente varió entre 439 y
508 m en septiembre y julio, respectivamente.
289
Figura 2. Esfuerzo y CPUE, total y comercial (> 130 mm AC), de cangrejo dorado (Chaceon chilensis), entre julio de
2005 y mayo de 2006.
Figure 2. Effort and CPUE for the total and commercial (> 130 mm AC) golden crab (Chaceon chilensis) fishery between
July 2005 and May 2006.
A partir de los datos obtenidos, se determinó una
captura de 13.903 ejemplares, de los cuales 10.863
(78,1%) fueron desembarcados por su interés comercial. La captura de hembras resultó notoriamente con
apenas 354 ejemplares, de las cuales 48 portaban huevos, que dado su menor tamaño relativo, no fueron
desembarcadas. Además, se observó la presencia recurrente de manchas oscuras y eventuales perforaciones
en la caparazón de los ejemplares.
De las 831 trampas viradas, 116 presentaron fauna
asociada correspondiente a 334 ejemplares de centolla
de Juan Fernández (Paromola rathbuni), además de la
presencia ocasional de anguila (Gymnothorax porphyreus) en trampas caladas en el rango de menor profundidad, aproximadamente a 300 m. A mayor profundidad se detectó ocasionalmente anguila blanca (Bassanago albescens), el gastrópodo Fusitritron magellanicum y un equinodermo sin identificar.
La CPUE promedio de cangrejo dorado fue 88,7
ind salida-1, equivalente a 69,2 ejemplares comerciales
por salida. Tomando en cuenta la unidad de esfuerzo
de pesca en términos de trampa virada, el rendimiento
promedio fue 16,7 ind trampa-1, en tanto que la CPUE
promedio de ejemplares comerciales (mayores a 130
mm de ancho cefalotorácico) fue 13,5 ind trampa-1
(Tabla 1).
Al desglosar los rendimientos de pesca mensualmente, éstos variaron entre 11,7 y 24,3 ind trampa-1 en
diciembre y abril, respectivamente. Los rendimientos
de las capturas comerciales, estuvieron comprendidos
entre 8,4 (septiembre) y 20,3 ind trampa-1 (abril). Por
sexo, se registró una marcada diferencia en el rendimiento de pesca, siendo el promedio en machos de
16,1 ind trampa-1, mientras que en hembras, sólo 0,4
ind trampa-1 (Tabla 2).
A partir de una muestra de 264 ejemplares, con
longitudes cefalotorácicas entre 82,6 y 142,2 mm y
peso entre 309 y 1.768 g, se efectuó el ajuste de la
relación de poder de talla (LC)-peso total en machos.
Según el ajuste no lineal, se obtuvieron los siguientes
parámetros: a = 0,0004 (Error estándar: 0,000067) y b
= 3,0694 (Error estándar: 0,032472).
Con respecto al muestreo sistemático realizado para desarrollar la evaluación directa, el recurso objetivo
fue capturado en las tres zonas (Fig. 3), entre 300 y
1000 m de profundidad. De esta manera, la captura
total fue 1.165 ejemplares, de los cuales 1.120
290
Tabla 1. Promedio mensual y coeficiente de variación (%) de la captura total y comercial obtenida por salida de pesca y
por trampa (n° ejemplares), en faenas de pesca de cangrejo dorado, temporada 2005/2006.
Table 1. Monthly average and coefficient of variation (%) for the total and commercial catch obtained per fishing trip and
per trap (no. of specimens) in golden crab fishery operations (2005-2006).
Mes
N°
ind salida-1
N°
ind comerciales salida-1
N°
ind trampa-1
N°
ind comerciales trampa-1
Julio 2005
59,0 (63,2%)
39,7 (65,0%)
14,6 (55,3%)
10,8 (50,6%)
Agosto
46,0 (88,0%)
38,1 (91,5%)
13,2 (58,1%)
11,7 (47,1%)
Septiembre
56,4 (68,7%)
35,9 (70,7%)
12,3 (61,1%)
8,4 (50,6%)
Octubre
96,6 (61,3%)
72,9 (42,6%)
16,4 (50,5%)
12,7 (39,7%)
Noviembre
119,6 (41,4%)
93,4 (51,3%)
16,0 (60,4%)
12,6 (68,9%)
Diciembre
52,9 (71,4%)
49,6 (73,7%)
11,7 (54,0%)
11,0 (54,0%)
Enero 2006
69,8 (59,4%)
57,8 (48,7%)
16,6 (56,7%)
13,7 (55,5%)
Febrero
86,2 (59,2%)
80,7 (61,0%)
15,8 (59,5%)
15,2 (58,8%)
Marzo
121,3 (64,1%)
97,1 (64,2%)
19,5 (47,8%)
15,9 (50,3%)
Abril
233,4 (43,3%)
189,0 (42,0%)
24,3 (63,0%)
20,3 (55,7%)
Mayo
232,8 (43,4%)
165,5 (44,3%)
23,0 (52,7%)
16,3 (53,2%)
Promedio
88,7 (87,0%)
69,2 (87,0%)
16,7 (62,0%)
13,5 (60,0%)
Tabla 2. Promedio mensual y coeficiente de variación (%) de la CPUE (n° ind trampa-1), mensual, por sexo y condición
de los ejemplares (ovígera, no ovígera), en faenas de pesca de cangrejo dorado, temporada 2005-2006.
Table 2. Monthly average and coefficient of variation (%) of CPUE (no. of specimens trap-1) by sex and condition of the
specimens (ovigerous, not ovigerous), in golden crab fishery operations (2005-2006).
machos
hembras no ovíferas
hembras ovíferas
Mes
N°
ind trampa-1
N°
ind trampa-1
N°
ind trampa-1
Julio 2005
10,3 (55,3%)
0,31 (221,6%)
0,03 (479,5%)
Agosto
13,0 (58,2%)
0,21 (295,4%)
0,06 (481,5%)
Septiembre
12,1 (61,4%)
0,11 (309,0%)
0,02 (655,7%)
Octubre
16,3 (51,1%)
0,14 (288,3%)
0,02 (640,3%)
Noviembre
15,6 (61,8%)
0,36 (223,0%)
0,01 (745,0%)
Diciembre
11,4 (53,9%)
0,24 (322,1%)
0,05 (416,2%)
Enero 2006
15,9 (59,7%)
0,57 (208,7%)
0,07 (648,1%)
Febrero
15,8 (59,3%)
0,05 (616,4%)
-
Marzo
18,5 (50,5%)
0,84 (262,6%)
0,08 (780,2%)
Abril
23,8 (61,7%)
0,49 (283,6%)
0,04 (465,4%)
Mayo
22,6 (51,9%)
0,23 (263,4%)
0,14 (284,6%)
Promedio
16,1 (62,4%)
0,35 (312,0%)
0,05 (610,5%)
291
Figura 3. Lances de pesca en las zonas de pesca empleadas para la evaluación directa de cangrejo dorado (Chaceon chilensis), alrededor de islas Robinson Crusoe y Santa Clara (Zona 1: Cerro Alto, Zona 2: Bahía Cumberland y Zona 3: Puerto Francés).
Figure 3. Fishing hauls done along fishing zones used for direct golden crab (Chaceon chilensis) assessment around Robinson Crusoe and Santa Clara islands (Zone 1: Cerro Alto, Zone 2: Bahía Cumberland, Zone 3: Puerto Francés).
(96,1%) fueron machos y 45 (3,9%) hembras, de éstas,
sólo dos portaban huevos.
En esta etapa, y al considerar la información batimétrica, los mayores rendimientos de pesca de machos
se registraron entre 400 y 500 m, alcanzando 19,5 y
15,5 ind trampa-1, mientras que las hembras se capturaron exclusivamente en la estación de 300 m (1,3 ind
trampa-1). Del mismo modo, sólo se registraron hembras portadoras en las estaciones de 500 y 600 m, con
rendimientos promedio inferiores a 1,0 ind trampa-1
(Tabla 3).
A partir de la experiencia de separación sucesiva
de trampas de pesca, para estimar la CPUE promedio
de acuerdo a las diferentes distancias consideradas, se
ajustó la siguiente función (valor-p < 0,05) (Tabla 4):
cpue s = 23,51
( 1 − exp−0,036⋅s )
De acuerdo a esto, se estimó un radio de atracción
(ratr) de 53,5 m, equivalente a un área de atracción
(Aatr) de 9.007,5 m2. A partir del ajuste de la probabilidad de captura respecto de la distancia (m = 1,0, n =
0,072), se obtuvo finalmente un radio efectivo de pesca (ref) de 13,4 m, equivalente a un área efectiva de
pesca (Aef) de 564,1 m2.
El sector delimitado por la posición de los lances
de pesca estuvo localizado al NE de las islas Robinson
Crusoe y Santa Clara, comprendido entre 300 y 600 m
de profundidad, con una superficie estimada en 45,8
km2.
Así, para el primer escenario, consistente en la estimación del radio de influencia de la trampa (13,4 m),
se estimó una biomasa vulnerable de 1.002 ton para el
área explotada, equivalente a 832.983 ejemplares.
Considerando con fines comparativos el segundo escenario y tomando en cuenta los radios de atracción
reportados en literatura (30 m), la biomasa vulnerable
de C. chilensis fue de 203 ton, que corresponde a
168.587 ejemplares sobre la talla comercial.
DISCUSIÓN
La pesca comercial de Chaceon chilensis en el archipiélago Juan Fernández, es una actividad reciente,
pues sus operaciones comenzaron aproximadamente el
año 2000, a partir de la realización de un proyecto de
pesca exploratoria efectuado en 1996 y 1997, que
identificó a esta especie como el principal recurso
marino con potencial para diversificar la pesca artesa-
292
Tabla 3. Capturas por trampa (unidades) de cangrejo dorado, por sexo y condición de los ejemplares, durante el experimento de separación de trampas en líneas de pesca (M: macho, HO: hembra ovígera, H: hembra).
Table 3. Golden crab catches per trap (units) by sex and condition of the specimens during the experiment of trap separation on fishing lines (M: male, HO: ovigerous female, H: female).
Profundidad (m)
300
400
500
600
700
800
900
1000
Total (300-1000)
Zona 1
Cerro Alto
Zona 2
Bahía Cumberland
Zona 3
Puerto Francés
Total general
12,67
10,33
2,33
0,00
26,67
26,67
0,00
0,00
11,83
11,83
0,00
0,00
4,83
4,83
0,00
0,00
2,50
2,33
0,17
0,00
0,83
0,83
0,00
0,00
0,50
0,50
0,00
0,00
8,55
8,19
0,36
0,00
8,50
7,50
1,00
0,00
16,67
16,17
0,50
0,00
8,50
7,50
0,83
0,17
11,50
10,33
1,00
0,17
4,20
4,20
0,00
0,00
0,50
0,50
0,00
0,00
0,00
0,00
0,00
0,00
7,20
6,66
0,49
0,05
22,00
21,33
0,67
0,00
16,00
15,83
0,17
0,00
27,33
27,17
0,17
0,00
5,67
5,50
0,17
0,00
2,67
2,67
0,00
0,00
4,00
3,83
0,17
0,00
1,83
1,83
0,00
0,00
5,67
5,67
0,00
0,00
10,65
10,48
0,17
0,00
14,39
13,06
1,33
0,00
19,78
19,56
0,22
0,00
15,89
15,50
0,33
0,06
7,33
6,89
0,39
0,06
3,06
3,00
0,06
0,00
1,78
1,72
0,06
0,00
0,78
0,78
0,00
0,00
5,67
5,67
0,00
0,00
8,89
8,55
0,33
0,02
nal en esas islas (Arana, 2000a). A la fecha, esta actividad ha sido desarrollada únicamente por algunas
embarcaciones, de manera complementaria a la extracción del principal recurso objetivo, la langosta de
Juan Fernández (Jasus frontalis).
Total
M
H
HO
Total
M
H
HO
Total
M
H
HO
Total
M
H
HO
Total
M
H
HO
Total
M
H
HO
Total
M
H
HO
Total
M
H
HO
Total
M
H
HO
A partir de los datos de las operaciones comerciales de pesca, se determinó que la proporción sexual
indicó un fuerte predominio de machos, con un promedio global de 97,5%. Este hecho es coincidente con
lo indicado por Arana (2000a), quien en faenas de
Tabla 4. Parámetros de la función ajustada entre CPUE y
separación entre trampas, para obtener el radio de atracción de las trampas.
Table 4. Parameters of the adjusted function between the
CPUE and the separation between the traps used to obtain their radii of attraction.
Límite
inferior
Límite
superior
Parámetro
Valor
a
23,523
19,44
27,577
b
0,036
0,013
0,0599
pesca exploratoria realizadas en la misma zona en
1997, destacó la ausencia de hembras en prácticamente todos los lances de pesca. La tendencia antes mencionada fue igualmente confirmada en el muestreo
sistemático realizado en la presente investigación en
torno a la isla Robinson Crusoe, en que el porcentaje
de machos fue de 96,1%.
En este sentido, proporciones sexuales con marcadas diferencias entre machos y hembras es un hecho
que ha sido documentado en diversos Geryonidae, y
puede ser atribuida a la estratificación espacial de los
sexos, batimétrica o latitudinalmente, tal cual ha sido
reportado en C. maritae, C. affinis, C. quinquedens y
C. fenneri (Kendall, 1990; Poupin et al., 1991; Lindberg & Lockhart, 1993; Pinho et al., 2001; LópezAbellán et al., 2002; Carvalho et al., 2009) y en C.
notialis (P. Pezzuto, com. pers.), o a la menor capacidad de las trampas para capturar hembras (Otwell et
al., 1984).
De este modo, se ha reportado en C. maritae y C.
fenneri la presencia y predominio de hembras en el
rango de menor profundidad de su distribución (Lux et
al., 1982; Lindberg & Lockhart, 1993), y en el caso de
C. affinis, en el de mayor profundidad (Pinho et al.,
2001; López-Abellán et al., 2002). Al respecto, en el
presente estudio, pese a las escasas capturas de hembras, los mayores rendimientos se obtuvieron en trampas caladas a menor profundidad, alrededor de los 300
m, zona donde las capturas se mezclan con Paromola
rathbuni (Retamal & Arana, 2000), cangrejo Homolidae no explotado comercialmente en estas islas.
Este hecho indicaría que la captura ocasional de
hembras de C. chilensis se debe a que éstas ocuparían
zonas someras, no vulneradas en la actualidad por la
actividad pesquera. Esta distribución resulta favorable
a la liberación, desarrollo y dispersión larval, dada la
mayor temperatura relativa a esa profundidad, como
ha sido sugerido en C. quinquedens (Kelly et al.,
1982; Lindberg & Lockhart, 1993).
293
Al respecto, el muestreo sistemático precisó que si
bien la actividad pesquera comercial se concentró
entre 375 y 525 m, el cangrejo dorado se distribuye, al
menos, entre 300 y 1000 m. De esta manera, su presencia está asociada al Agua Intermedia Antártica
(AIAA), cuyo núcleo se ubica a 600 m y se caracteriza
por mínimos relativos de salinidad menores a 34,3,
oxígeno disuelto con máximos relativos mayores a 2
mL L-1 y temperaturas de 5°C. Entre 200 y 400 m de
profundidad, se asocia a la presencia de P. rathbuni, y
se caracteriza por la presencia del Agua Ecuatorial
Subsuperficial (AESS), que tiene un máximo relativo
de salinidad de 34,5 y bajo contenido de oxígeno disuelto, menor a 2 mL L-1 (Arana et al., 2006). Por lo
tanto, la presencia eventual de hembras de C. chilensis
en torno a 300 m se asociaría a la profundidad de mezcla entre ambas masas de agua.
El lapso de once meses que abarcó el monitoreo,
sugería la detección de procesos asociados a reproducción o muda. Sin embargo, la presencia esporádica de
hembras impidió precisar el período de portación; no
obstante, se registraron ejemplares con huevos en
todos los meses, a excepción de febrero, obteniéndose
la mayor CPUE en mayo (0,14 hembras portadoras
por trampa), lo cual indicaría un largo período de portación, como en Chaceon fenneri (Erdman & Blake,
1988).
Igualmente, las capturas no mostraron signos claros que pudiesen dar indicios de períodos de muda. No
obstante, la presencia recurrente de manchas y lesiones oscuras en la caparazón, que han sido detectadas
también en Chaceon quinquedens y atribuidas a la
acción de bacterias (Bullis et al., 1988; Young, 1991),
la distinta coloración del exoesqueleto y la presencia o
ausencia de epibiontes, pudiesen ser utilizadas como
futuros indicadores del proceso de ecdisis en esta especie.
La CPUE mensual, entre julio 2005 y mayo 2006,
varió entre 11,7 y 24,3 ind trampa-1, rango superior al
obtenido por Arana & Vega (2000), quienes reportaron intervalos promedio entre 3,5 y 8,1 kg trampa-1,
equivalentes a 4,0 y 9,3 ind trampa-1, durante pescas
experimentales efectuadas de marzo a junio de 2007,
entre 175 y 626 m de profundidad, empleando aparejos de similar diseño al actual. La diferencia anterior
puede ser atribuida a incrementos en el poder de pesca, producto de mejoras en la eficiencia de captura,
debido al desarrollo de la actividad comercial de pesca
sobre este cangrejo.
Temporalmente, la CPUE aumentó entre julio de
2005 y mayo de 2006 (Fig. 1), pasando de 10,8 a 16,3
ejemplares comerciales por trampa. Dichos resultados
deben ser examinados considerando las variaciones en
el nivel de esfuerzo, y especialmente, conforme a la
294
incorporación de caladeros no explotados con anterioridad en el área sur de Robinson Crusoe, durante abril
y mayo (Fig. 2). Según el peso promedio de cada
ejemplar (0,937 kg), la CPUE expresada en peso, resultaría superior a los rangos medios reportados por
Pezzuto et al. (2002) para la flota cangrejera en Brasil
de C. ramosae y C. notialis (1,8 y 4,5 kg trampa-1) en
2001 y 2002.
Con relación a la evaluación de biomasa vulnerable, se consideró las limitaciones impuestas, tanto por
la distribución del recurso objetivo, como por las dificultades operacionales asociadas a una pesquería artesanal, lo cual llevó a descartar el empleo de opciones
metodológicas utilizadas en otras especies de cangrejos, como marcaje o fotografía submarina (Miller
1975; Melville-Smith, 1985). Del mismo modo, los
resultados de este trabajo se deben considerar de
acuerdo a los diversos supuestos del método empleado
(Arena et al., 1994), destacando el área circular de
influencia en torno al aparejo, además de factores que
afectan las tasas de captura, como el tiempo de reposo,
variaciones en el grado de atracción por la carnada, o
la saturación de trampas, entre otros (Miller, 1990).
En este sentido, el radio estimado es inferior al
considerado en evaluaciones directas de distintas especies de los géneros Chaceon y Geryon, el cual ha
variado entre 25 y 35 m (McElman & Elner, 1982;
Melville-Smith, 1986; Defeo et al., 1990; Pezzuto et
al., 2001), que también es menor al estimado por Barea & Defeo (1985) en C. quinquedens (33 m) e idéntico al estimado por Aedo & Arancibia (2003) para
Cancer porteri (13,5 m). Lo anterior se puede atribuir
a la alta imprecisión del método de evaluación directa,
a la escasez de experiencias específicas de estimación
del radio de influencia, así como a diferencias conceptuales respecto de la definición del área de influencia
del aparejo de pesca de los autores indicados, con
relación a lo indicado por Aedo & Arancibia (2003).
Al respecto, los parámetros estimados de la función utilizada para calcular la CPUE asintótica presentaron varianzas importantes (Tabla 4), reflejando la
multiplicidad de factores que pueden afectar su estimación, como la presencia y variación de corrientes
marinas, o la correcta operación de los aparejos sobre
el fondo marino, entre otros. La mayor parte de la
información disponible relativa a la aplicación del
método en Geryonidae (McElman & Elner, 1982;
Defeo et al., 1990; Pezzuto et al., 2001), no considera
estimaciones específicas del radio de atracción, a excepción de Barea & Defeo (1985) y Melville-Smith
(1986), quienes calculan el área efectiva relacionando
la CPUE mediante trampas, con fotografía submarina.
El enfoque empleado en la estimación del área de
atracción del aparejo difiere del tradicional, expuesto
por Arena et al. (1994), autores que consideran como
equivalentes los radios de atracción y efectivo de pesca. En este sentido, se puede demostrar que conforme
a la aproximación metodológica de Aedo & Arancibia
(2003), dado que n = ln(0,02) / ratr , se verifica que
ref = 0,25 ratr , lo cual podría explicar la similitud
entre los radios estimados por dichos autores para C.
porteri, aplicado en el presente estudio, debido a la
baja variación del radio efectivo, ante un cambio unitario en el radio de atracción.
De acuerdo al radio de influencia estimado (13,4
m), la densidad de C. chilensis alcanzaría 181,9 ind
ha-1. Al tomar en cuenta un radio de 30 m, ésta correspondería a 36,8 ind ha-1.
Sin embargo, el comparar la estimación de densidad respecto a lo indicado por otros investigadores
para Geryonidae, lamentablemente no contribuye a la
discusión. En efecto, los valores publicados presentan
alta variabilidad, por cuanto en C. maritae se han reportado densidades de 145,2 ind ha-1 (Melville-Smith,
1986), de 40 a 230 ind ha-1 mediante muestreo con
trampas, y sobre 350 ind ha-1 empleando fotografía
submarina (Melville-Smith, 1985). Igualmente, Wenner & Barans (1990) reportan sólo 1,9 ind ha-1 en C.
fenneri mediante observaciones directas con sumergibles.
Como alternativas futuras, se podría considerar opciones de evaluación directa de C. chilensis tales como
marcaje, método que ha sido considerado como el más
preciso en C. maritae (Melville-Smith, 1988; Le
Roux, 2001) o la fotografía submarina, enfoque de
mayor costo. Así, el marcaje podría ser un método
directo de estimación, o utilizarse como validación del
radio de influencia, ya sea contrastando sus resultados
con las densidades estimadas con trampas, o permitiendo la estimación de los parámetros de la curva de
probabilidad de captura al interior del área de atracción (McQuinn et al., 1988).
De acuerdo a lo expuesto, tanto la existencia de
una actividad comercial incipiente a la fecha, así como
los niveles de biomasa vulnerable estimadas, indican
que la explotación de C. chilensis es una opción viable
de diversificación para la pesca artesanal en el archipiélago de Juan Fernández. En este sentido, dado que
la extracción a la fecha ha estado circunscrita a una
fracción de la distribución del recurso, de aproximadamente 45,8 km2, sin que ésta se realice alrededor a
la totalidad de los fondos marinos con profundidades
aptas para la presencia del cangrejo alrededor a Robinson Crusoe y Santa Clara, existen posibilidades de
expansión de las faenas a potenciales caladeros de
pesca localizados al sur y oeste de ambas islas, a la
isla Alejandro Selkirk y además, a los montes submarinos adyacentes del cordón submarino de Juan Fernández.
AGRADECIMIENTOS
Los autores agradecen a todos quienes facilitaron las
labores de recopilación de datos en la isla Robinson
Crusoe. En especial, a quienes desarrollaron tareas de
muestreo a bordo, Sres. Waldo Chamorro P., Oscar
Schiller C., Daniel Chamorro B., Julio Chamorro S.,
Daniel de Rodt S., David de Rodt S., Francisco Gallardo P., Maikel Pérez G., Robinson González A. y
Manuel Chamorro R., y Srtas. Ana Jesús Contreras R.
y María A. Erices O., además de los patrones de las
embarcaciones “Margarita”, “Guaitecas” y “Don Pedro”, Sres. Pedro Chamorro, Mario Llanquín y Danilo
Rodríguez, respectivamente, en cuyas naves se realizó
gran parte del presente estudio. Igualmente, al Oceanógrafo, Sr. Pedro Apablaza B., quien tuvo a su cargo
las tareas de jefe de base en Robinson Crusoe durante
el desarrollo de este proyecto, y a los evaluadores del
presente trabajo por sus oportunos aportes y recomendaciones.
Este artículo fue generado como parte de los proyectos “Monitoreo biológico-pesquero de la langosta y
el cangrejo dorado en el archipiélago de Juan Fernández (FIP N°2004-48) y “Evaluación de stock y distribución de la langosta y el cangrejo dorado en el archipiélago de Juan Fernández (FIP N°2005-21).
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Sexual maturity of Chaceon ramosae
297
Research Article
Sexual maturity of the deep-sea royal crab Chaceon ramosae Manning, Tavares &
Albuquerque, 1989 (Brachyura: Geryonidae) in southern Brazil
1
Paulo Ricardo Pezzuto1 & Rodrigo Sant’Ana1
Universidade do Vale do Itajaí, Centro de Ciências Tecnológicas da Terra e do Mar, Rua Uruguai, 458
CEP 88.302-202, Itajaí, SC, Brazil
ABSTRACT. The royal crab Chaceon ramosae is one of the three species of deep-sea crabs currently exploited in Brazil. The royal crab fishery started in 2001 with foreign vessels that were extensively monitored
by observers and tracked by satellite. A management plan implemented in 2005 was based only on biomass
dynamics, as biological knowledge of the resource was limited at that date. Samples taken aboard were used to
determine size at first sexual maturity for males and females by studying the use of allometric growth of chelae and abdomen in relation to carapace width (CW), the proportion of females with opened vulvae and eggs
in the pleopods, and males showing copula marks on the first ambulatory legs. Morphometric maturity was attained, on average, at 12.1 cm (males) and 10.7 cm (females). The CW50% was estimated to be 10.9 cm and
12.2 cm for females, respectively considering the vulva condition and eggs in the pleopods, and 13.6 cm for
males. By size class, the maximum estimated proportions of ovigerous females by size class was 0.4 and of
males with copula marks was 0.6, suggesting a bi-annual reproductive cycle for individuals of the species. The
size composition analysis showed that immature individuals may comprise up to 70% of the catches. These results indicate the need to consider enhanced trap selectivity and lower mortality of ovigerous females as new
and immediate goals to improve resource management.
Keywords: deep-water resources, reproduction, trap fisheries, relative growth, sexual maturity, Geryonidae,
Chaceon ramosae, continental slope, Brazil.
Madurez sexual del cangrejo real Chaceon ramosae Manning, Tavares & Albuquerque,
1989 (Brachyura: Geryonidae) en el sur de Brasil
RESUMEN. El cangrejo real Chaceon ramosae corresponde a una de las tres especies de cangrejos de profundidad que actualmente se explotan en Brasil. La pesca de cangrejo real comenzó en el año 2001 por barcos
extranjeros que eran intensamente supervisados por observadores y rastreados por satélites. En el año de 2005
se implementó un plan de manejo, considerando solamente el estudio de la dinámica de la biomasa del recurso, ya que el conocimiento biológico todavía era limitado. A partir de muestras obtenidas a bordo de los barcos
de pesca, se estimó la talla de primera madurez de machos y hembras a través de la utilización del crecimiento
alométrico de la quela y el abdomen con respecto al ancho del caparazón (CW), proporción de hembras con
vulvas abiertas y huevos en los pleópodos, y machos con marcas de cópula en las primeras patas ambulatorias.
La madurez morfométrica de los machos fue obtenida en promedio a 12,1 cm CW y en las hembras a 10,7 cm
CW. El CW50% fue estimado en 13,6 cm en machos y, en hembras considerando la condición de la vulva o los
huevos en los pleópodos, en 10,9 y 12,2 cm respectivamente. La máxima proporción estimada de hembras
ovígeras y machos con marcas de cópula por talla fueron de 0,4 y 0,6 respectivamente, lo que sugiere que el
ciclo reproductivo a nivel individual es bi-anual. El análisis de la composición de tallas evidenció que individuos inmaduros componen hasta el 70% de las capturas. A partir de estos resultados, se consideró incrementar
el efecto selectivo de las trampas y disminuir la captura de hembras ovígeras, como objetivos nuevos e inmediatos para mejorar el manejo de este recurso.
Palabras clave: recursos de profundidad, reproducción, pesca con trampas, crecimiento relativo, madurez
sexual, Geryonidae, Chaceon ramosae, talud continental, Brasil.
________________________
Corresponding author: Paulo Ricardo Pezzuto ([email protected])
298
INTRODUCTION
Geryonid crabs are widely distributed around the continental slopes of the world ocean (Hastie, 1995) and
sustain commercial fisheries on both sides of the Atlantic. Chaceon maritae is fished for along southwestern Africa (Melville-Smith, 1988); C. quinquedens is
targeted from Canada throughout the southeastern
United States, where a fishery for C. fenneri also takes
place (Erdman & Blake, 1988; NEFMC, 2002); and C.
notialis has been exploited in Uruguayan waters since
the 1990s (Defeo & Masello, 2000; Delgado & Defeo,
2004).
Following the worldwide expansion of industrial
fisheries to deep-water areas (Morato et al., 2006),
since the end of the 1990s, the formerly coastal-based
Brazilian fishing industry has directed longline, gillnet, trawl, and trap operations to previously unexploited grounds on the slope and seamounts, searching
for new and valuable bottom resources, including
deep-water crabs (Peres & Haimovici, 1998; Perez et
al., 2002, 2003; Pezzuto et al., 2006a, 2006b; Haimovici et al., 2007; Carvalho et al., 2009).
Revealed by trap vessels in 2001, commercial concentrations of the endemic deep-sea royal crab Chaceon ramosae (Manning et al., 1989) soon became the
target of up to eight foreign processor vessels chartered by national companies. The species was also the
most abundant and valuable by-catch item for several
gill-netters and trawlers that targeted other deep-sea
resources, namely monkfish (Lophius gastrophysus)
and aristeid shrimps, in the same areas (Perez &
Wahrlich, 2005; Pezzuto et al., 2006b). Annual royal
crab landings (live weight) recorded between 2001
and 2005 ranged from 495 to 1,252 tons (mean = 789
ton yr-1), including both directed and incidental
catches.
The intense monitoring of trap vessels by observers
and vessel monitoring systems (VMS) has resulted in
a large fishery-based data set that was used to identify
the species distribution and generate preliminary estimates of stock biomass and maximum sustainable
yields (Pezzuto et al., 2002, 2006a). A management
plan for the royal crab fishery was established in May
2005, based mostly on the biomass dynamics of the
stock, including total allowable catch (600 ton live
weight year-1, corresponding to the maximum sustainable yield), maximum number of permits (3 vessels),
maximum number of traps per vessel (900 units), and
minimum mesh size in traps (100 mm stretched). Biological measures such as minimum legal sizes, closed
areas/seasons, or sex-selective harvest strategies
would have been considered in the plan but no lifecycle parameters were available for the species at the
time, even though biological data had been intensively
collected by the onboard observers.
Given their high value and k-strategist life-traits,
geryonid crabs are expected to be highly vulnerable to
over-exploitation, requiring severe fishing regulations
for their sustainability (see review by Hastie, 1995).
Given the need to improve the royal crab management
plan with biological reference points, this paper investigates the sexual maturity of C. ramosae that are vulnerable to a directed fishery in southern Brazil and
analyses the annual size structure of the catches, quantifying the contribution of “immature” and “mature”
individuals in the fishery.
MATERIAL AND METHODS
Data source
The maturity analysis was carried out with biological
data collected by observers during 21 commercial trips
conducted between 2002 and 2005 by the F/V Royalist. Measuring 35.7 m total length, this factory vessel
operated in Brazilian waters from May 2001 to June
2006. During the study period, nearly 19,200 crabs
were sampled at the main fishing ground of the species (i.e. 25° to 31°S and 300 to 1,100 m depth) (Table
1, Fig. 1).
The size structure of the global catches, totaling
33,238 individuals, was studied using information
collected simultaneously by observers on another
seven commercial vessels operating in the same areas.
Besides the data collected aboard, biological samples (frozen crabs) were regularly obtained for laboratory analysis. Nearly 50% of these specimens were
collected aboard the F/V Royalist and the remaining
came from the other vessels. Detailed information on
most vessels and traps used in the royal crab fishery
are available in Pezzuto et al. (2006a).
Sampling
Observers recorded the date, position, depth, number
of traps line-1, soaking time, catch haul-1 (kg), and
mean number of crab trap-1 for all hauls. Biological
sampling was carried out on hauls selected by the
observers in order to cover different depths and latitudes, according to the fishing strategy used by the
vessel’s captain. Most vessels worked simultaneously
with four trap lines. The maximum interval between
successive samplings was 48 h and the mean soaking
time of each line was 42.3 h (± 6.9 h). Crabs were
randomly selected from traps positioned in the beginning, middle and end sections of the main line. Their
sex was determined and their carapace width (CW,
distance between the fifth antero-lateral spine tips)
299
Table 1. Chaceon ramosae. Number of trips, hauls, and crabs sampled annually aboard the F/V Royalist in southern Brazil for size-at-maturity analysis.
Tabla 1. Chaceon ramosae. Número de viajes, lances de pesca y muestreo de cangrejos a bordo del F/V Royalist en el sur
de Brasil para el análisis de la madurez sexual.
Year
Trips
Hauls
Males
Females
Total
Depth range (m)
2002
2003
2004
2005
Total
4
7
6
4
21
60
142
149
82
433
1,916
4,880
5,067
1,991
13,854
454
1,380
2,281
1,158
5,273
2,370
6,260
7,348
3,149
19,127
504 – 1,010
508 – 947
435 – 1,020
345 – 918
-
Figure 1. Map showing the main fishing area for Chaceon ramosae in southern Brazil during the study period (gray area).
The 100, 200, 500, and 1000 m isobaths are indicated.
Figura 1. Mapa de la área principal de pesca de Chaceon ramosae en el sur de Brasil durante el período estudiado (área
gris). Se indican las isóbatas de 100, 200, 500 y 1000 m.
was measured to the nearest millimeter. Males were
classified according to the presence or absence of
copula marks (blackened areas in the merus of the
second pereiopods, see Melville-Smith, 1987) on 125
hauls. Vulva condition (i.e. closed/immature or
opened/mature; Delgado & Defeo, 2004) and the presence of eggs in the pleopods were recorded for females sampled from 285 and 180 hauls, respectively.
Frozen crabs were processed in the laboratory according to the same procedures used aboard, but de-
tailed measurements of body parts were also obtained
for the relative growth analysis of secondary sexual
characteristics (Hartnoll, 1982). Measurements were
conducted with sliding calipers to the nearest 0.5 mm
and included: abdomen width (AW, measured between the 4th and 5th abdominal somites), left and
right cheliped lengths (LChL and RChL, maximum
length of the upper portion of the propodus), and left
and right maximum cheliped height (LChH and
RChH, maximum height of the propodus measured in
its exterior face).
300
Data analysis
Morphometric maturity was studied by analyzing the
relative growth of 1,090 crabs processed at the laboratory (511 males, 579 females). A visual examination
of scatter plots for several body parts versus CW (reference dimension) showed no clearly identifiable transition points in the data associated with morphometric
maturity (Hartnoll, 1982). Therefore, an allometric
equation (Y = a Xb) was fitted to the data by least
squares regression and the transition points were iteratively searched by a specific routine of the software
Regrans (Pezzuto, 1993). This routine seeks the CW
value where the data could be split in two subsets
resulting in the lowest combined residual sum of
squares. A statistical test for coincidental regressions
was conducted in order to check the validity of the
transition points. The test compares the difference
between the global sum of squares (i.e. calculated
from a single model fitted to the data), and the pooled
residual sum of squares (i.e. of the subsets located to
the left and right sides of the transition point) (Zar,
1996). If a significant difference was found,
ANCOVA (α = 0.05) was used to test the difference
between the elevation and slopes of the two regressions, corresponding to the pre and post-pubertal
growth phases (Zar, 1996).
The relative growth pattern (i.e. negative allometric, isometric, or positive allometric) of each body
dimension and phase (pre and post-pubertal) was identified by testing the allometric coefficient (slope)
against the reference value “1” (Zar, 1996).
Functional/sexual maturity was studied by estimating the mean sizes (CW50%) at which males and females are able to copulate and reproduce. Proportions
of males showing copula marks and females with
opened vulvae and eggs in the pleopods were calculated for 1-cm size (CW) classes, considering the total
number of individuals caught during the hauls sampled aboard. The total numbers in the catches were
previously estimated by multiplying the numbers in
the samples by the ratio between the total catch weight
and the sample weight. Proportions of ovigerous females were only analyzed on trips carried out between
January and June, the main reproductive season of the
species (Pezzuto et al., 2006c).
A non-linear minimum squares estimation procedure was then used to fit a generalized logistic model
(Restrepo & Watson, 1991) to the data as follows:
PCW =
β
( α1 −α 2 CW )
1+ e
(1)
where PCW is the proportion of individuals in each size
class, and α1, α2, and β are parameters. In this model,
β is a more general parameter that allows for the asymptotic proportion of the model to be lower than or
equal to 1. Therefore, a penalty function for β ≤ 1 was
included in the parameter estimation procedure. This
is of special interest for management purposes as it
can indicate the maximum theoretical proportion of
individuals presenting the maturity criteria in the largest size classes in a given period/area of study. Size at
50% maturity was given by the equation:
α
CW50% = 1
α2
(2)
Confidence intervals for CW50% were estimated by
a bootstrap procedure in which frequency distributions
of individuals with copula marks, opened vulvae, and
eggs in the pleopods were randomly resampled 250
times, resulting in a corresponding number of logistic
curves for each case. Given the asymmetrical distribution of the results, the median of the 250 CW50% estimates were calculated and the 2.5 and 97.5% percentiles were used as 95% confidence limits (Haddon,
2001).
The size-structure of the global catches was analyzed by sex in terms of the proportion of mature and
immature individuals fished per year, considering all
the individuals sampled aboard the eight vessels targeting C. ramose in the period. Before pooling the
data from these vessels, trips, and hauls, the numbers
sampled by size class and sex were raised to the total
caught in the respective hauls following the same
procedure described for the fuctional/sexual maturity
analysis.
RESULTS
Morphometric maturity
The relative growth of males showed significant transition points at 12.1 cm (CW) for all dimensions but
AW, whose relationship with CW was described by a
single model (Table 2, Fig. 2). Allometry in the
growth of the chelae was always positive (b > 1) irrespective of the dimension (width or height) or subset
considered (pre or post-pubertal phase), but the regressions calculated for crabs larger than 12.1 cm
revealed a significant increase in their elevation (suggesting a sudden increase in chelae size) and a reduction in their slopes (Table 2, Fig. 2).
Compared to the males, the females had more variable relative growth patterns. Transition points were
found for all variables (including AW) and fluctuated
mostly between 10.7 and 11.0 cm CW (Table 2, Fig.
3). Allometry was always positive before the transition points (pre-pubertal phase). However, in the post-
301
Table 2. Chaceon ramosae. Regressions (Y = a Xb) fitted between carapace width (CW) (independent variable) and abdomen width (AW), left chelae length (LChL), left chelae height (LChH), right chelae length (RChL), and right chelae
height (RChH) by sex. t-value: tests for Ho: b = 1 *: p < 0.05; **: p < 0.01, DF: degrees of freedom.
Tabla 2. Chaceon ramosae. Regresiones (Y = a Xb) ajustadas entre el ancho del caparazón (CW) (variable independiente)
y ancho del abdomen (AW), largo de la quela izquierda (LChL), altura de la quela izquierda (LChH), largo de la quela
derecha (RChL) y altura de la quela derecha (RChH) por sexo. Valor de t: test para Ho: b = 1 *: p < 0,05; **: p < 0,01,
DF: grados de libertad.
Sex
Males
Females
Body
dimension
Transition point
(CW, cm)
Subset
a
b
r²
t-value
DF
AW
-
Total
0.1835
1.1432
0.975
17.365**
501
LChL
12.1
Left
0.1629
1.1981
0.958
12.656**
256
Right
0.2202
1.1054
0.866
3.556**
217
LChH
12.1
Left
0.1279
1.2483
0.959
15.238**
254
Right
0.1892
1.1183
0.856
3.767**
216
RChL
12.1
Left
0.1770
1.1904
0.958
12.252**
257
Right
0.2309
1.1053
0.867
3.545**
215
RChH
12.1
Left
0.1542
1.2018
0.955
12.275**
253
Right
0.2039
1.1125
0.833
3.295**
215
AW
10.7
Left
0.1303
1.4701
0.962
20.956**
172
Right
0.2051
1.3009
0.784
8.136**
344
LChL
11.0
Left
0.1830
1.1193
0.965
7.696**
193
Right
0.3048
0.9122
0.655
- 2.146*
264
LChH
10.7
Left
0.1477
1.1600
0.968
9.536**
162
Right
0.2311
0.9777
0.716
- 0.613
289
RChL
11.0
Left
0.1934
1.1178
0.963
7.481**
195
Right
0.3410
0.8856
0.598
- 2.522*
259
RChH
9.8
Left
0.1648
1.1424
0.949
5.602**
111
Right
0.2441
0.9779
0.761
- 0.738
339
pubertal phase, the growth pattern of females became
isometric for ChH and negative for ChL, yet remained
positive for AW (Table 2, Fig. 3).
Functional/sexual maturity
The smallest male exhibiting copula marks measured
9.3 cm CW. A value of only 0.58 was estimated for
the parameter β of the logistic function, as the proportion of males with darkened areas on their legs never
reached 100% for any size class (Fig. 4). The onset of
sexual maturity in males (CW50%) occurred at 13.6 cm
with a confidence interval distinctly skewed to the
bigger sizes (12.8-15.8 cm) (Table 3).
The smallest female with opened vulvae was 7.4
cm CW. The proportion of individuals in this condi-
tion increased continuously with size, attaining 100%
in females larger than 13 cm (β = 1) (Fig. 4). The
CW50% estimated by bootstrap was 10.9 cm with a
narrow and almost symmetrical confidence interval
(Table 3). Compared to the vulva condition, the presence of eggs in the pleopods suggested that sexual
maturity in females was attained at larger sizes. The
carapace width of the smallest ovigerous female was
8.0 cm and the respective CW50% increased from 10.9
cm (opened vulvae) to 12.2 cm (Table 3, Fig. 4). Additionally, despite that fact that more than 90% of the
females larger than 12.2 cm presented opened vulvae,
the proportion of females carrying eggs during the
main reproductive period did not surpass 0.41 (Table
3, Fig. 4).
302
Figure 2. Chaceon ramosae. Plots of relative growth of chelipod and abdomen dimensions for males. Arrows indicate
transition points between different growth phases.
Figura 2. Chaceon ramosae. Relaciones de crecimiento relativo de las dimensiones de la quela y abdomen para los machos. Las flechas indican los puntos de transición entre diferentes fases de crecimiento.
Size-structure
Figure 5 shows the global size structure of the royal
crab catches recorded between 2002 and 2005. Males
(3.9-19.2 cm) were larger than females (4.9-17.0 cm).
The size frequency distribution of males was bimodal,
peaking at 11.25 and 14.25 cm, whereas females displayed a narrower distribution with a single mode at
12.25 cm. In both sexes, the catches were slightly
asymmetrical for the smaller individuals.
The size catch composition analysis pointed out
different scenarios depending on the maturity criterion
considered. Throughout all the study period, the mean
percentage of immature females in the catches varied
from 15.9% (morphometric maturity) to 63.9% (functional maturity). For males, the participation of immature individuals fluctuated in a much narrower interval, varying from 33.1% to 54.8% (Table 4). On the
other hand, the incidence of juveniles in the catches
during the course of the fishery showed an inverse
pattern for the sexes, irrespective of the maturity criterion chosen for the analysis. Whereas the amount of
immature females decreased from 2002 to 2004, the
numbers of undersized males increased continuously
in the same period. Both functionally immature males
and females peaked in 2005, with 66% and 70%, respectively (Table 4).
303
Figure 3. Chaceon ramosae. Plots of relative growth of chelipod and abdomen dimensions for females. Arrows indicate
Figura 3. Chaceon ramosae. Relaciones de crecimiento relativo de las dimensiones de la quela y abdomen para las hembras. Las flechas indican los puntos de transición entre diferentes fases de crecimiento.
Table 3. Chaceon ramosae. Parameters (α1, α2, and β) of the logistic curves (± CI 95%) fitted to the proportion of females with opened vulvae, ovigerous females, and males showing copula marks by size class and the corresponding sizeat-maturity (CW50% ) estimated by the bootstrap procedure.
Tabla 3. Chaceon ramosae. Parámetros (α1, α2 y β) del modelo logístico (± CI 95%) ajustados a la proporción de hembras con vulvas abiertas, hembras ovígeras y machos con marcas de cópula por clases de talla y las correspondientes tallas
de primera madurez (CW50%) estimadas por un procedimiento bootstrap.
Parameters
β
α1
α2
Bootstrap
CW50% (cm)
Females
Opened vulvae
Mean
CI (95%)
1.00
0.97-1.06
14.55
11.39-17.71
1.32
1.03-1.61
Median
10.94
CI (2.5-97.5%)
10.59-11.11
Mean
0.40
11.56
0.94
Median
12.24
Ovigerous
CI (95%)
0.37-0.44
8.58-14.53
0.69-1.19
CI (2.5-97.5%)
10.55-15.83
Males
Copula marks
Mean
CI (95%)
0.58
0.55-0.62
12.93
10.51-15.35
0.95
0.77-1.14
Median
13.61
CI (2.5-97.5%)
12.83-15.79
304
Figure 5. Chaceon ramosae. Size-frequency distribution
of males and females caught in commercial fisheries in
southern Brazil between 2002 and 2005.
Figura 5. Chaceon ramosae. Distribución de frecuencia
de tallas de machos y hembras capturados por la pesca
comercial en el sur de Brasil entre 2002 y 2005.
DISCUSSION
Figure 4. Chaceon ramosae. a) Logistic model (solid
line) fitted to the observed proportion (dashed line) of
males showing copula marks, b) females with opened
vulva, and c) eggs in the pleopods. Note the differences
among Y-axis values.
Figura 4. Chaceon ramosae. a) Modelo logístico (línea
continua) ajustado a la proporción observada (línea discontinua) de machos con marcas de cópula, b) hembras
con vulvas abiertas, c) huevos en los pleópodos. Note las
diferencias entre los valores de los ejes Y.
In this paper, the determination of size at maturity
considered a scenario of indeterminate growth for C.
ramosae, i.e. a non-terminal pubertal moult. In a recent paper, Delgado & Defeo (2004) estimated size-atmaturity for females of C. notialis under hypotheses of
indeterminate and determinate growth, as MelvilleSmith (1987) suggested the existence of a terminal
moult for C. maritae females. In addition, Steimle et
al. (2001) considered determinate growth for C. quinquedens based on evidence supposedly obtained by
Lux et al. (1982) and Lawton & Duggan (1998).
In spite of some controversy in the literature, we
agree with Hines (1990): there is no real evidence to
support a true terminal moult in the group. MelvilleSmith’s (1987) assertion for C. maritae (see page 270)
was preliminary and not based on any explicitly demonstrated data. In fact, in a seminal paper on the
growth and age of the species (Melville-Smith, 1989),
the author was categorical that: “a small number or
recaptured females (three or 1.6 per cent) did moult
after being tagged as mature animals. It therefore appears that mature females are capable of moulting
more than once, but that there is probably a lengthy
interval between moults. The longest period over
which a mature female remained unmoulted was 1,217
days (3.3 years). The fact that few females reach 110
mm CW, suggests that it is unlikely that they moult
more than twice after maturity”. In another paper dealing with mark-and-recapture techniques, Lux et al.
(1982) found that some C. quinquedens females were
305
Table 4. Chaceon ramosae. Percentages of immature and mature individuals in the commercial catches by sex and year,
according to the different criteria of sexual maturity. SD: standard deviation.
Tabla 4. Chaceon ramosae. Porcentaje de individuos inmaduros y maduros en las capturas comerciales por sexo y año
según distintos criterios de determinación de madurez sexual. SD: desviación estándar.
Females
Year
2002
2003
2004
2005
Mean
SD
Males
Relative growth
Opened vulvae
Eggs in the pleopods Relative growth Copula marks
(10.7 cm)
(10.9 cm)
(12.3 cm)
(12.1 cm)
(13.6 cm)
Immature Mature Immature Mature Immature Mature Immature Mature Immature Mature
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
16.6
83.4
23.7
75.4
64.6
27.4
26.6
73.5
48.0
52.0
16.0
84.0
23.3
74.9
62.4
31.1
30.5
69.5
52.7
47.4
11.1
89.0
18.8
80.9
58.2
34.9
30.6
69.4
52.8
47.2
19.9
80.1
31.5
70.3
70.3
34.8
44.8
55.2
65.6
34.4
15.9
84.1
24.3
75.4
63.9
32.0
33.1
66.9
54.8
45.2
3.6
3.6
5.3
4.3
5.0
3.6
8.0
8.0
7.6
7.6
recaptured as ovigerous, mostly up to three years after
being released although, two individuals were recaptured after five and seven years. These authors concluded that sperm stored since the last pretagging
moult would remain viable for several years in the
species and that, as found by Melville-Smith (1989),
intermoult periods increase with age. However, a terminal moult was never suggested. On the contrary,
they suggested that immature females mate after the
pubertal moult and that mature females mate again
after a subsequent moult (Lux et al., 1982). Attrill et
al. (1991) discussed in detail the possibility of a terminal ecdysis in G. trispinosus and concluded that
evidence for this is inconclusive but that it is possible
that males and females stop growth two and four instars after the pubertal moult, when they are significantly larger than their respective sizes at maturity.
Finally, although explicitly indicating a terminal moult
for C. quinquedens, Lawton & Duggan (1998) do not
clearly demonstrated any data in their paper that support this. It seems, therefore, that much more data on
Geryonidae reproduction and growth patterns are necessary to better develop and support a terminal moult
hypothesis for the group.
Table 5 summarizes maximum sizes and sexual
maturity data available for several Geryonidae species.
The sizes at maturity estimated for both sexes (12.113.6 cm for males and 10.7-12.3 cm for females) as
well as the range of sizes observed for ovigerous females in this study (8.0-16.2 cm) coincide with the
general values reported for the group. In fact, estimates produced for C. ramosae were closer to those
found for C. affinis, C. fenneri, and C. granulatus,
which are all among the largest species in the family.
Sizes at morphometric maturity are attained before
the individuals of both sexes are functionally mature.
In fact, relative growth changes occurred in males at
12.1 cm, whereas sexual activity revealed by copula
marks was identified, on average, only at 13.6 cm. In
females, both allometric changes and opened vulvae
were observed at CWs 1.3 cm smaller than the CW50%
estimated for ovigerous females. Because gonadal
development was not investigated in this study, we
were not able to conclude whether physiological and
morphometric maturity are synchronous or not in the
species. Physiological maturity seems to be correlated
with changes in the relative growth pattern of secondary sexual traits and/or the vulvae condition, at least
in C. quinquedens, C. maritae, C. fenner, C. chilensis,
and C. notialis (Haefner Jr.; 1977; Melville-Smith,
1987; Erdman & Blake, 1988; Delgado & Defeo,
2004; Guerrero & Arana, 2009). On the other hand,
first gonadal development is attained before (males) or
after (females) morphometric maturation in C. affinis
(Fernández-Vergaz et al., 2000). Whatever the size of
C. ramosae at physiological maturity, the finding that
morphometric maturity is attained before males copulate and females are able to oviposit and incubate eggs
indicates that changes in form should play a role in the
reproductive success of the species. Notwithstanding,
it is noteworthy that changes in relative growth patterns in the morphometric maturity of C. ramosae
were much more difficult to identify than in many
other Brachyura such as, for instance, Majidae, Ocypodidae, and Pinnotheridae (e.g. Carmona-Suárez,
2003; Negreiros-Fransozo et al., 2003; Alves et al.,
2005). In fact, changes in allometry patterns in Geryonidae have been found to be very subtle or even in
306
Table 5. Summary of size-at-maturity values estimated for male and female geryonid crabs. When available, overall size ranges (including mature and/or immature
individuals) of the samples are included for comparison among the species. Except for C. bicolor, C. chilensis and G. trispinosus, which were measured in terms of
carapace length (CL), all values refer to carapace width, in centimeters. Methods of analysis are indicated as: a) morphometric data/relative growth, b) vulva condition, c) visual examination of abdomen development, d) smallest ovigerous female, e) gonadal development, f) mean size of ovigerous females, g) percentage of
ovigerous females by size class, and h) copula marks; ?: not specified.
Tabla 5. Resumen de tallas de primera madurez estimadas para machos y hembras de cangrejos gerionídeos. Cuando estaban disponibles, los rangos de tallas (incluyendo individuos maduros y/o inmaduros) en las muestras fueron incluidos para efecto de comparación entre las especies. Todas las medidas se refieren al ancho del caparazón, en centímetros, con excepción de C. bicolor, C. chilensis y G. trispinosus, cuyas medidas fueron el largo del caparazón (CL). Los métodos de
análisis están indicados como: a: datos morfométricos/crecimiento relativo, b: condición de la vulva, c: examen visual del desarrollo del abdomen, d: hembra ovígera de menor tamaño, e: desarrollo gonadal, f: talla promedia de hembras ovígeras, g: porcentaje de hembras ovígeras por clase de talla, h: marcas de cópula, ?: no
especificado.
Females
Species
Chaceon affinis
Males
Ovigerous size
range
Overall size range
9.9a ; 10,8c, e ; 11,3 b
10.2 – 11.8b; 11.4f
> 12.0
9.8 – 13.2
6.1 - 16.5
5.5 – 16.5
12.9 a
-
6.5 – 18.9
5.0 – 19.0
Pinho et al. (2001)
13.2 f
11.5 – 16.5
6.1 – 16.5
-
5.2 – 18.9
López-Abellán et al. (2002)
e
Overall size range
Chaceon bicolor
-
-
-
9.4 (CL)
Chaceon chilensis
-
-
-
10.0(CL) a
4.6-19.0
-
8.5 – 17.0
-
8.8 – 19.3
Chaceon fenneri
9.7b, e
8.5 - 10.0
Chaceon granulatus
Chaceon maritae
Source
Size-at-maturity
Size at
maturity
b, e, g
5.9-16.3 (CL)
Fernández-Vergaz et al. (2000)
Hall et al. (2006)
Guerrero & Arana (2009)
Wenner et al. (1987)
9.7 - 14.7
8.9 - 15.6
-
-
Erdman & Blake (1988)
-
11.0 – 14.3
-
-
-
Hines (1988)
-
13.4 – 17.0
11.4 – 17.4
> 6.2d
6.2 – 10.2
6.0 – 10.4
8.3a
-
8.4 – 10.0b
-
?
12.4 – 17.9
Hastie & Sounders (1992)
-
6.5 – 16.4
Beyers & Wilke (1980)
-
-
-
-
7.6 – 8.0 e, h
Gaertner & LaLoé (1986)
Melville-Smith (1987)
6.5
-
-
-
-
Diop & Kojemiakine (1995)
Chaceon notialis
7.0 – 9,1a, b, e
-
4.6 – 11.4
-
-
Delgado & Defeo (2004)
Chaceon quinquedens
8.0 - 9.1a, b, e, g
9.7 - 13,1
-
-
-
Haefner (1977)
10.3f
-
7.0 – 13.1
-
6.0 – 16.3
-
9.0 – 11.8
-
Chaceon ramosae
Chaceon sp. (= C. poupini)
Geryon trispinosus
10.7-12.3
a, b, f, g
a
h
McElman & Elner (1982)
Hines (1988)
8.0 – 16.2
4.9 – 16.8
12.1 ; 13.6
3.9 – 19.0
This study
8.2 a ; > 9.0 b
-
4.6 – 15.3
-
5.1 – 17.4
Poupin & Buat (1992)
1.2 – 1.5 (CL) a;e
> 2.0 (CL)
~ 0.5 – 5.0 (CL)
3.5 (CL) a
~ 0.5 – 7.5 (CL)
Attrill et al. (1991)
existent under visual or statistical analyses (e.g.
Haefner, 1977; Gaertner & Laloé, 1986; FernándezVergaz et al., 2000; Pinho et al., 2001; Delgado &
Defeo, 2004; Hall et al., 2006), rendering morphometric data very limited for estimating size at the onset of
morphometric maturity in this group. The small geryonid Geryon trispinosus is probably an exception as
its pubertal moult is characterized by significant
changes in the relative growth of the abdomen and
right chelae of females and males, respectively (Attrill
et al., 1991).
It is possible that the absence of remarkable allometric changes in Geryonidae result from constraints associated with mating behavior and survival
in deep-water environments. Laboratory observations
demonstrate that mating is a relatively prolonged
process in Geryonidae. Males display a pre-copulatory
behavior, forming a protective cage around the receptive female by using their locomotory legs. Preecdysis is then initiated in the female, lasting several
days, and mating starts just after her ecdysis. The
copulatory embrace lasts 7 to 11 days, during which
the male actively protects the vulnerable soft-shelled
female (Elner et al., 1987; Erdman & Blake, 1988). A
similar behavior was described by Hartnoll (1969) as a
common pattern in aquatic members of Cancridae and
Portunidae, which recognize individuals for mating
relying mostly on chemical and tactile stimuli (Type
I). On the contrary, copula in several other Brachyura,
including semi-terrestrial members of Grapsidae and
Ocypodidae, is conducted with hard-shelled females
and lasts only some minutes. A brief courtship occurs
and recognition between individuals is based mostly
on visual, tactile, and even auditory stimuli (Type II)
(Hartnoll, 1969), in which we expect secondary sexual
traits to play a very significant role for sexual attraction and selection.
Christy (1987) distinguished eight kinds of mating
associations in brachyuran crabs based on apparent
modes of competition among males for mates. According to this classification, behaviors similar to
those described above for Geryonidae should be expected in aquatic species in which receptive females
are relatively uncommon, dispersed, mobile, and mate
infrequently. In these cases, males tend to search for
receptive females that release pheromones and defend
them from other competing males; this seems to agree
with the general knowledge about mating in Geryonidae. Considering this “search-and-defend” strategy
(sensu Christy, 1987) and the opportunistic scavenging/predatory behavior reported for geryonid crabs
(Hastie, 1995; Kitsos et al., 2005; Domingos et al.,
2007, 2008), the increase in general body size might
play a more significant role in the survivorship and
307
reproductive success of the group than, for instance,
disproportionate chelae growth. Investing in a bigger
body should improve the locomotory ability of the
crabs and, consequently, their capacity to locate mates
and food resources that are dispersed widely over the
sea-bed. In addition, a larger size should reduce the
costs of body maintenance, as less energy should be
spent per unit biomass, a key advantage in an
oligotrophic environment (Gage & Tyler, 1991).
In a recent article, Bonduriansky (2007) argued
that strong positive allometries in secondary sexual
traits might even be exceptions in nature, especially in
traits not totally dedicated to reproductive activities
but primarily involved in individual maintenance (e.g.
locomotory and sensorial appendices). In these cases,
the gains obtained with disproportionate growth of the
allometric trait, in terms of sexual selection, can be
surpassed by viability costs of exaggeration, which
might interfere with the general performance of the
individual (e.g. movement, food acquisition). A similar reasoning was used by Attrill et al. (1991) to explain the relative reduction of the chela size in G.
trispinosus males at the pubertal moult. As the male
needs to carry the female for mating, the optimal outcome for the individuals could be a maximal increase
in body size at maturity to allow successful courtship,
making chela growth a lower priority. It is likely,
therefore, that the lack of strong changes in allometry
in the chelae of Geryonid males could reflect an absence or weakness of selective pressures for sexual
selection in the group.
The maximum theoretical proportion of males exhibiting copula marks (parameter β of the logistic
function) was only 0.58 in C. ramosae. Three hypotheses can be posed to explain this relatively small
value: a) abrasion marks are not necessarily formed on
all recently paired males; b) a proportion of the recently paired males may have moulted before being
caught; and c) not all mature males copulate in each
reproductive season. The first hypothesis could be
supported by Melville-Smith’s (1987) finding that no
copula marks are found on very large males of the red
crab C. maritae (CW > 120 mm), as their merus do
not chafe against the female carapace when she is
carried during the pre-copulatory embrace and mating.
However, in C. ramosae, even the largest individuals
exhibited copula marks on their legs. In addition,
Melville-Smith’s findings on the disappearance of
copula marks on large-sized red crabs did not explain
why only 60% of the mature C. ramosae individuals
of intermediate sizes had damaged shells, assuming
that they all should have been abraded if mating had
occurred. Moulting details are not known for the royal
crab, precluding testing of the second hypothesis. On
308
the other hand, the low growth rates attributable to
geryonids and the increasing intermoult periods expected for large individuals (Lux et al., 1982; Melville-Smith, 1989; Arana, 2000) render improbable the
moulting of nearly 40% of the adult males (i.e. eliminating the respective copula marks along with their
old shells) between the last copula and their catch. The
hypothesis that not all mature males copulate during
each reproductive season will be analyzed in conjunction with the female pattern of sexual activity and
maturity.
The maximum theoretical proportion of ovigerous
females in any size class did not surpass 40% in C.
ramosae. Proportions smaller than 100% would be
expected: a) if the catchability of breeding females is
reduced due to behavioral limitations (e.g. reduced
activity, difficulty for climbing the traps), and/or
availability on the fishing grounds (Melville-Smith,
1987; Hastie & Saunders, 1992; Poupin & Baut, 1992)
and/or, inevitably, b) if breeding among individuals in
the population is not simultaneous during the reproductive season, such that some adult females are bearing eggs whereas others are not at the moment of being caught. The latter condition would be easily satisfied if females produced more than a single batch per
season, since some time interval would occur between
batches. In this case, only a fraction of the whole reproductively active population would be ovigerous at
any time, resulting in a β parameter of the logistic
model that is smaller than 1. However, evidence in the
literature suggests that geryonid crabs have long
breeding periods lasting 6 to 9 months (Hinsch, 1988;
Erdman & Blake, 1988; Attrill et al., 1991; Erdman et
al., 1991). Under this scenario, a maximum of 40% of
the ovigerous C. ramosae females in any size class of
the catch would characterize its reproduction as annual
at the population level, as spawning takes place from
January to June in areas shallower than 700 m
(Pezzuto et al., 2006c), but would be nearly bi-annual
at the individual level; this would also agree with the
relatively small proportion of mature males exhibiting
copula marks. Although this hypothesis should be
better investigated, it is important to keep in mind that
bi-annual cycles were suggested for C. affinis, C. fenneri and C. quinquedens, and were interpreted by
some authors to be a consequence of the food-limited
characteristic of deep-water environments (Erdman &
Blake, 1988; Erdman et al., 1991; Pinho et al., 1998;
López-Abellán et al., 2002). If confirmed, this biannual strategy would render the royal crab stock
extremely vulnerable to the overfishing of recruits.
Analyzing the percentages of immature crabs in the
commercial catches reveals very distinct scenarios
depending on the criteria used for determining size at
sexual maturity. Considering the sizes at morphological maturity for both sexes and the vulva condition in
females, commercial fleet operations are characterized
by a relatively small proportion of immature individuals. More conservatively, however, when determining
maturity through data on ovigerous females and males
with copula marks, more than 50% of the catches
between 2002 and 2005 corresponded to sexually
immature individuals, with a severe peak of more than
70% in 2005. The excessively high and certainly biologically unsafe proportions of immature crabs in the
catches were similar between the sexes, suggesting at
least a relatively uniform impact of the fishery on the
population structure of the resource.
Global landings of C. ramosae exceeded the estimated maximum sustainable yield (MSY) in most
years (Pezzuto et al., 2006c) and included ovigerous
females whose catches are not yet limited. This fact,
combined with the actual size composition of the
catches and the hypothesis of a bi-annual reproductive
cycle for the species, renders the fishery highly unsustainable. Therefore, the current management regime of
the royal crab fishery should be improved by incorporating new regulations based on biological considerations. The new regulations should emphasize enhanced trap selectivity and the implementation of
spatial-temporal restrictions on effort allocation in
order to diminish the participation of immature individuals of both sexes and ovigerous females in the
catches, contributing to the biological sustainability of
the resource. In fact, based on the results of this paper
and those of Pezzuto et al. (2006c), the management
of the royal crab fishery has been changed very recently, incorporating, inter alia, an increased permitted minimum mesh size in the traps (from 100 to 120
mm stretched) and the annual closure of the spawning
areas < 700 m depth from January 1 to June 30. As the
vessels engaging in the fishery should be obligatorily
monitored by observers on all trips, biological data
will soon be available in order to verify the efficacy of
these changes and to refine them, if necessary, in a
continuous process of adaptive management.
ACKNOWLEDGEMENTS
The authors are indebted to all the observers, whose
hard work resulted in most of the high-quality data
available for this study, and to José Angel Alvarez
Perez (CTTMar/UNIVALI) for the critical reading of
the first version of this manuscript. The kind assistance provided by Helia del Carmen Farias Espinoza
(CTTMar/UNIVALI) with the Spanish version of the
Abstract and captions is fully appreciated. This work
was funded by the Special Secretary of Aquaculture
and Fisheries (Brazilian Government – SEAP/PR/
001/2003; SEAP/PR/078/2004; SEAP/PR/ 064/2005
and SEAP/PR/027/2007) and by a research grant to
PRP from the National Research Council (CNPq)
(Process 310820/2006-5).
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Crecimiento, mortalidad y evaluación de Chaceon chilensis
Research Article
Crecimiento, mortalidad y evaluación de la población de cangrejo dorado
(Chaceon chilensis) explotado en el archipiélago de Juan Fernández, Chile
1
Cristian Canales1 & Patricio M. Arana2
Departamento de Evaluación de Recursos, División de Investigación Pesquera
Instituto de Fomento Pesquero, Blanco 839, Valparaíso, Chile
2
Casilla 1020, Valparaíso, Chile
RESUMEN. Se analiza la información mensual de composición de tamaño recopilada en el monitoreo de la
pesca artesanal sobre cangrejo dorado (Chaceon chilensis) realizado entre julio de 2005 y mayo de 2006, para
evaluar los parámetros de crecimiento, mortalidad natural y puntos biológicos de referencia de los machos sobre los cuales se basa esta pesquería. Se estableció una longevidad promedio de 20 años y una mortalidad natural en torno a M = 0,27 año-1. La talla crítica se determinó a los 110 mm de longitud cefalotorácica (Lc), que
es levemente inferior a la talla de primera captura de 114 mm de Lc. De acuerdo al análisis efectuado, se explotan individuos entre 4 y 10 años de vida. Mediante análisis de equilibrio se determina que la población se
encuentra en 82% de la condición virginal, que se refleja en una talla promedio en las capturas de 128 mm de
Lc. Una eventual reducción de la población a un límite del 40% de la condición original, se consigue aumentando en tres veces el nivel actual de desembarques, lo que se traduciría en una talla media en las capturas de
118 mm de Lc. Finalmente, se recomiendan distintos puntos biológicos de referencia para garantizar una explotación sustentable en el tiempo.
Palabras clave: crecimiento, mortalidad, evaluación, cangrejo dorado, Chaceon chilensis, archipiélago de
Juan Fernández, Chile.
Growth, mortality, and stock assessment of the golden crab (Chaceon chilensis)
population exploited in the Juan Fernández archipelago, Chile
ABSTRACT. Monthly information on the size composition of golden crab (Chaceon chilensis) catches compiled while monitoring the artisanal fishery (July 2005 through May 2006) is analyzed in order to evaluate the
growth parameters, natural mortality, and biological reference points in male specimens, the basis of the fishery. Average longevity was found to be 20 years and natural mortality around M = 0.27. The critical size was
determined to be around 110 mm carapace length (Lc), slightly lower than that of the first catch (114 mm Lc).
According to this analysis, individuals between 4 and 10 years of age are exploited. A balance analysis revealed that 82% of the population is virginal, as reflected in an average size-at-catch of about 128 mm Lc. Tripling the current level of landings would lead to an eventual reduction to a limit of 40% of the original population; this would result in an average catch size of 118 mm Lc. Finally, several biological reference points are
recommended for guaranteeing sustainable exploitation over time.
Keywords: growth, mortality, stock assessment, golden crab, Chaceon chilensis, Juan Fernandez Archipelago,
Chile.
________________________
Corresponding author: Cristian Canales ([email protected])
313
314
INTRODUCCIÓN
La existencia del cangrejo dorado de Juan Fernández
(Chaceon chilensis Chirino-Gálvez & Manning, 1989)
se determinó como resultado de la campaña de pesca
exploratoria realizada en torno a las islas Robinson
Crusoe y Santa Clara durante 1996 y 1997. La abundancia detectada como el gran tamaño de los ejemplares capturados motivó que fuera catalogado como
recurso potencial, transformándose en una opción para
los pescadores artesanales de la isla, quienes tradicionalmente han dependido exclusivamente de la extracción de la langosta de Juan Fernández (Jasus frontalis)
(Arana, 2000). Se debe destacar que la distribución
batimétrica del recurso a profundidades mayores a 200
m planteó nuevos requerimientos en términos del
equipamiento de las embarcaciones, haciendo necesario contar con equipos viradores mecánicos o hidráulicos (Arana & Vega, 2000; Martínez & Alvarez, 2000).
La abundancia de cangrejo dorado favoreció el desarrollo de una pesca experimental para establecer el
aparejo de pesca más adecuado para su extracción y
definir su distribución batimétrica, con énfasis en
precisar si existían diferencias en los rendimientos por
trampas respecto a la profundidad (Arana & Vega,
2000). Los resultados permitieron identificar que la
fracción explotable de la población estaba constituida
prácticamente por machos (98%), no teniendo mayores antecedentes respecto de la ubicación y atributos
poblacionales de las hembras (Arana, 2000). De
acuerdo a las estadísticas oficiales de desembarque, el
desarrollo de la pesquería de cangrejo dorado de Juan
Fernández se inicia a partir del año 2000. Primeramente se registra una captura de 13 ton, que luego se incrementa obteniéndose un total de 40 ton en 2004,
para luego descender hasta 2 ton el 2006 debido principalmente a falta de poder comprador. Esta es una
pesquería nueva y aún no se encuentra regulada por la
autoridad pesquera chilena.
Estudios sobre parámetros biológicos del grupo
Geryonidae son escasos a nivel mundial, pero se sabe
que en algunas especies existe una fuerte competencia
talla-especifica en las capturas realizadas con trampa,
lo cual determina una mayor proporción de ejemplares
grandes (Miller, 1989), Por otro lado, Haefner (1978)
postuló que estos animales requerirían de a lo menos
15 mudas para alcanzar la talla máxima. Así también,
en estudios de marcaje se ha determinado que estos
cangrejos presentan un crecimiento lento y que las
capturas están compuestas por individuos viejos, de
seis o más años (Lux et al., 1982).
Dada la importancia que reviste la explotación de
esta especie para la comunidad pesquera del archipiélago de Juan Fernández y la necesidad de establecer
bases biológicas para un manejo sustentable, en el
presente trabajo se determina los parámetros de crecimiento, mortalidad natural, madurez sexual y talla
crítica. Con este fin se analiza la información mensual
recopilada en la temporada de pesca 2005/2006, con la
cual se establece el estado de situación del cangrejo
dorado y sus puntos biológicos de referencia.
Información analizada
Entre julio 2005 y mayo 2006, se realizaron actividades de monitoreo de esta pesquería desarrollada alrededor de las islas Robinson Crusoe y Santa Clara del
archipiélago de Juan Fernández (Arana et al., 2006b).
El área de estudio se localizó aproximadamente entre
33º35´-33º50´S y 78º40´-79º50´W, y las actividades
extractivas cubrieron profundidades entre 200 y 1.000
m (Fig. 1). Se registró información en 155 salidas de
pesca, se revisaron 813 trampas y se muestreó más de
13.000 individuos que corresponde al 94% de la captura total (Arana et al., 2006b).
Cabe destacar, que una de las características especiales de esta pesquería es que la población vulnerada
por los aparejos de pesca está constituida solo por
machos, lo cual determina el análisis realizado sólo
involucra a este sexo. Los individuos medidos fueron
agrupados en rangos de 2 mm longitud cefalotorácica
(Lc), con el objeto de amortiguar la variabilidad de
medición y rescatar de mejor forma la distribución de
frecuencia de tallas en las capturas.
Parámetros de crecimiento
Los parámetros del modelo de crecimiento de Von
Bertanlanffy fueron determinados mediante la descomposición modal de las estructuras de tallas, donde
cada componente modal se supone constituye un grupo de edad. El procedimiento aplicado consistió en
identificar estadísticamente distribuciones normales
subyacentes en las “nf” distribuciones de frecuencias
de tallas analizadas, según se ilustra en el paquete
computacional Elefan I (FAO) y el algoritmo Mix
(MacDonald & Pitcher, 1979), el cual fue programado
en Matlab V6.5 y resuelto bajo el principio de máxima
verosimilitud (Sparre & Venema, 1997). El uso simultáneo de la composición de talla permite identificar las
componentes modales con mayor precisión y objetividad, estimándose los parámetros de cada distribución
en respuesta a la repetición de cada componente a lo
largo de la muestra analizada
Al realizar el análisis se supone que una determinada estructura de tallas (i) se encuentra compuesta
por “na” distribuciones de edades, cada una de ellas
315
Figura 1. Distribución de las trampas empleadas en faenas de pesca de cangrejo dorado, entre julio de 2005 y mayo de
2006.
Figure 1. Distribution of the traps used in golden crab fishing operations between July 2005 and May 2006.
siguiendo una distribución de densidad normal cuya
talla media caracteriza cada grupo etario o estados de
muda, según sea el caso. De esta manera, en cada
grupo de edad (a) la talla media se establece como:
L a = L00 ( 1 − exp − k ) + exp − k L a −1
σ a = CV L a
(2)
(3)
Así, la composición de tallas de cada grupo modal
queda representada de la forma:
fˆl ,a ,i = π a ,i pl ,a ni
(4)
na
∑ π a ,i = 1
F̂l ,i =
(1)
donde L∞ y k son parámetros desconocidos por resolver, al igual que la talla modal del primer grupo de
edad ( L1 ). La proporción de individuos a la talla (l)
que comprende el a-ésimo grupo de edad queda representado por una distribución normal con media conocida (ec. 2) y desviación estándar σ, supuestamente
proporcional a la talla media modal mediante el coeficiente de variación (CV):
pl ,a ≈ N ( L a ,σ a2 )
i-ésima composición de tallas. De esta forma, la iésima composición de tallas muestral es estimada
sumando sobre cada componente modal:
(5)
a
donde π a,i es la proporción que compone cada grupo
modal-etario y n el tamaño de muestra observado en la
na
∑ f̂l ,a
(6)
a
El problema se resume en determinar en las muestras los parámetros de crecimiento, el coeficiente de
variación y las proporciones edad-específicas, de forma que minimicen el valor de un estimador de logverosimilitud penalizado, asumiendo para ello que la
composición de talla responde a una distribución multinomial. En esta distribución, se emplea un tamaño
muestral efectivo variable proporcional al tamaño de
muestra (mi) observado de la i-ésima composición de
tallas normalizado a 200 individuos, según:
log L =
L nf
∑∑ 200 ∑ mi i Fl ,i log( F̂l ,i ) + λ ( L00 − Λ )2
l
m
(7)
i
i
La penalización λ *( Loo − Λ)2 corresponde a una
restricción de los valores probables de la longitud
asintótica modelada mediante pérdida cuadrática en
torno a la talla de referencia “Λ”. Una vez resuelto el
vector de parámetros, se realizó un retro cálculo siguiendo la ec. 1 para evaluar la talla modal mínima
que podría tener un individuo de 1 año de edad y por
ende la asignación de edad en las siguientes compo-
316
nentes modales. Definido esto, esta misma aproximación permitió inferir el valor de t0 del modelo de Von
Bertanlanffy. Se supone que cada componente modal
es un grupo de edad, y al tener varias composiciones
de tallas, cada grupo de edad debiera reproducirse de
manera independiente en cuanto a la media y desviación estándar, variando solo la proporción relativa en
las frecuencias de tallas.
Método
Modelo de Taylor (1958)
Modelo de Alagaraja (1984)
Modelo de curva de captura (Z=M)
⎛ M ⎞
1
⎟⎟
log ⎜⎜
k
⎝ M + bk ⎠
Definición
bk
M=
b + k t0
M =
5
tmax
bk
M =
0 ,25 tmax k
−1
− ln( 0,01 )
M=
tmax
e
(8)
k y to son parámetros de crecimiento, y b
es el parámetro de alometría
(9)
tmax es la edad máxima
(10)
(11)
ln( Ca ) = φ − Z a (12)
Cabe señalar que en la aplicación del último modelo (curva de captura), se supone que la reciente actividad de pesca ha sido de bajo impacto y no ha alterado
la estructura de edad de la población, de manera que Z
= M. Aquí, la composición de edad de la captura se
genera de manera directa asignando la edad a la marca
de clase de cada intervalo de tallas.
La talla crítica fue estimada evaluando primero la
edad crítica y luego convirtiéndola a longitud
mediante el modelo de crecimiento. Esta edad, que
garantiza la máxima eficiencia de la pesquería respecto
del crecimiento somático de los organismos, fue
evaluada considerando la variación marginal de la
biomasa por recluta, afectada sólo por causas naturales
en relación con la edad. La edad crítica tcrit, corresponde
a la edad donde esta variación es igual a cero y
analíticamente conduce a la expresión derivada del
modelo de rendimiento por recluta de Beverton y Holt:
tcrit = t0 −
Para el cálculo de la tasa instantánea de mortalidad
natural se consideró el desempeño de diversos estimadores bio-analógicos, los cuales están basados en los
parámetros vitales del recurso, como crecimiento,
madurez sexual y longevidad. El detalle de los estimadores es:
Estimador
Modelo de Beverton & Holt (1956)
Alverson & Carney (1975)
Mortalidad natural (M) y talla crítica (tcr)
(13)
Análisis de equilibrio
El estado de situación del cangrejo dorado se determinó según el modelo de Thompson & Bell, simulando
una población estructurada en edad sometida a diferentes niveles de mortalidad por pesca. A partir de
esto, se evaluó la reducción relativa de la población
explotable y su talla promedio como índice de status a
ser comparada con la talla promedio observada. Para
Ca es la captura a la edad y φ intercepto
esto, a falta de mayor información, se supone que la
población se encuentra en promedio equilibrada en
relación con su estructura poblacional y los reclutamientos. El modelo poblacional considera la sobrevivencia de un reclutamiento unitario desde la edad (a)
de primera captura (tpc) a la edad máxima (tmax), de
acuerdo a:
1
⎧⎪
Na = ⎨
− Za −1
N
exp
⎪⎩ a −1
a=t
a = t pc + 1 : t max
(14)
y la captura por recluta corresponde al modelo de
captura de Baranov:
F N ( 1 − exp − Z a )
Cpr a = a a
Za
(15)
donde la mortalidad total Z es la suma de la mortalidad natural (M) y la mortalidad por pesca Fa , la cual
se define como:
F a= Fcr S a
(16)
siendo Fcr la mortalidad por pesca de los grupos
completamente reclutados y S a el patrón de explotación que considera los ejemplares de edad cuya talla
es mayor o igual a 114 mm de Lc (observado en la
pesquería).
⎧0 a < a( l < 114mm )
Sa = ⎨
⎩1 a ≥ a( l ≥ 114mm )
(17)
De igual modo, la biomasa explotable por recluta
(Bpr) se obtiene de la expresión:
Bpr =
∑ Sa Na Wa
(18)
a
lo cual permite evaluar en términos relativos la
reducción poblacional en el largo plazo para distintos
valores de Fcr. Aquí, Wa es el peso medio a la edad
estimada mediante la relación peso-talla aplicado a la
longitud media a la edad:
W a = q ( L a )b
(19)
donde los parámetros de esa relación corresponden a
los estimados por Arana et al. (2006) con q =
0,000428 y b = 3,069467. La talla media de los
ejemplares completamente reclutados para distintas
condiciones de explotación en equilibrio es una
respuesta al stress ocasionado por F y se estimó
proporcional a la talla media de la captura:
∑ La Cpra
L cr
a
∑ Cpra
(20)
a
Conocido el valor de la talla promedio de las
capturas monitoreadas (> 114 mm de Lc), se puede
establecer la comparación con el valor Lcr teórico, lo que
permite inferir en términos relativos el nivel de
reducción de la población virginal.
RESULTADOS
Crecimiento
Las composiciones de tallas de machos generadas en
el muestreo cubrieron ejemplares entre 46 y 189,7
mm de longitud cefalotorácica (Lc), con tallas medias
que fluctuaron mensualmente entre 114,4 y 130,3 mm
de Lc (Tabla 1). En una primera inspección mostraron
una persistente polimodalidad que se supone podrían
componer grupos de muda o de edad (Fig. 2). De igual
forma, cabe destacar que en los cinco primeros meses
del monitoreo, se registraron de manera significativa
los ejemplares más grandes, (140-160 mm Lc), situación que cambió radicalmente en los siguientes meses
(enero a mayo de 2006), cuando el grupo de los individuos más grandes se redujo al rango 120-140 mm de
Lc (Fig. 2).
Los datos registrados permitieron distinguir los
primeros 3 ó 4 grupos modales, pero luego y sobre la
base del supuesto de proporcionalidad entre la varianza y la talla media por grupo de edad, se generó una
superposición de componentes modales lo cual dificultó la identificación visual de estos grupos. El modelo aplicado supone que en la información disponible
317
existe un patrón subyacente en el crecimiento, y cuyas
componentes modales podrán variar de acuerdo con
factores no necesariamente atribuibles a una dinámica
de cohorte, como por ejemplo, zona de pesca, mes o
profundidad de captura.
En este estudio, se considera que todas las composiciones de tallas recopiladas aportan información,
pero su contribución o importancia relativa al ajuste es
ponderada considerando sus respectivos tamaños de
muestra. Uno de los parámetros de crecimiento relevantes es la longitud asintótica (L∞), que corresponde
al valor promedio de los ejemplares más grandes de
una población inexplorada y por ende no debería parecer extraño que el ejemplar más grande (189,7 mm de
Lc en abril del 2006) supere este valor promedio. La
talla promedio de los ejemplares más grandes alcanzó
los 170 mm de Lc (julio del 2005), valor que sirvió de
base para establecer una penalización de la longitud
asintótica según se indica en la ec. 7.
Siguiendo el procedimiento descrito, el ajuste
del modelo de crecimiento se realizó considerando
que la información disponible de este recurso en su
fase explotada no permite identificar más de ocho
componentes modales (o grupos de edades). Algunos ensayos previos consideraron supuestos de hasta 12 grupos de edad presentes en las capturas, pero
la relación de desviación estándar vs la talla modal
derivó, en general, en una importante superposición,
donde el considerar más de ocho grupos etarios es
irrelevante para mejorar el ajuste del modelo.
El ajuste y convergencia del modelo se logró luego
de 9.300 iteraciones. El resultado es un modelo que
reproduce con el mínimo error la forma y variabilidad
de cada una de las composiciones de tallas consideradas. El diagrama cuantil-cuantil (qq-plot) indica que
los datos observados y predichos provienen de la
misma distribución dado que se aproximan, salvo
algunas excepciones, significativamente a la linealidad, lo cual se verifica con la normalidad de los residuales (Fig. 3). La composición de talla de julio, agosto y septiembre de 2005 mostró una fuerte participación de individuos mayores a 140 mm de Lc, talla que
precisamente corresponde al grupo modal con los
ejemplares más grandes observados en el monitoreo
de esta pesquería (Fig. 4).
Los parámetros del modelo fueron 92, de los cuales
88 representan la proporción de cada grupo de edad en
las muestras mensuales de capturas (11 meses por 8
grupos) y los cuatro restantes corresponden a L∞, k, L1
y CV. Así, los parámetros de crecimiento estimados
indican que este recurso presentaría un incremento
corporal anual de moderado a lento, de k = 0,142 año-1
valor compatible con un recurso de mediana longevi-
318
Tabla 1. Principales estadígrafos de la longitud cefalotorácica en la captura total del cangrejo dorado, temporada 2005-2006 (Fuente: Arana et al., 2006b).
Table 1. Main statistics of the cephalothoracic length in the total golden crab catch for the 2005-2006 season (Source: Arana et al., 2006b).
Mes
N° ejemplares
muestreados
Media (mm)
Mediana (mm)
Desviación estándar (mm)
Mínimo (mm)
Máximo (mm)
Julio
Agosto
Septiembre
Octubre
Noviembre
Diciembre
Enero
Febrero
Marzo
Abril
Mayo
Total
Hembras
5
23
5
7
20
18
23
4
108
36
24
273
Machos
880
1.175
544
669
1.568
640
666
725
2.269
1.818
1.800
12.754
Totales
885
1.198
549
676
1.588
658
689
729
2.377
1.854
1.824
13.027
Hembras
95,2
104,9
106,6
98,0
91,4
92,3
94,3
96,3
90,8
90,2
92,3
95,7
Machos
124,6
124,3
129,8
118,2
119,4
120,1
117,6
119,2
113,4
113,0
114,0
119,4
Totales
124,5
123,9
129,6
118,0
119,1
119,3
116,8
119,1
112,5
111,9
113,5
118,9
Hembras
92,0
110,6
107,0
91,5
90,8
93,0
95,2
96,6
91,2
93,2
95,6
93,2
Machos
130,0
127,3
132,8
121,3
121,7
122,6
120,7
122,2
116,4
119,4
115,1
120,6
Totales
129,5
126,3
132,6
121,0
121,5
122,2
120,2
122,1
115,2
119,1
114,9
120,2
Hembras
9,8
12,3
5,1
22,3
5,7
3,1
5,6
3,5
6,8
7,3
7,5
8,1
Machos
20,0
19,1
17,4
17,1
15,1
13,4
15,0
13,9
14,5
14,8
14,2
15,9
Totales
20,1
19,2
17,5
17,2
15,4
14,0
15,3
13,9
15,0
15,3
14,4
16,1
Hembras
86,2
80,1
97,2
80,0
76,1
85,4
84,1
91,0
73,2
68,7
71,6
68,7
Machos
46,0
74,3
79,0
76,6
69,8
63,1
77,8
80,4
72,4
74,4
75,1
46,0
Totales
46,0
74,3
79,0
76,6
69,8
63,1
77,8
80,4
72,4
68,7
71,6
46,0
Hembras
114,0
117,2
111,2
150,0
101,1
98,0
103,6
100,9
112,9
107,1
109,4
150,0
Machos
177,4
165,0
162,1
165,6
148,7
153,7
153,7
153,7
147,1
189,7
170,4
189,7
Totales
177,4
165,0
162,1
165,6
148,7
153,7
153,7
153,7
147,1
189,7
170,4
189,7
319
0.05
0.05
Julio
n=880
0
80
Enero
n=666
100
120
140
160
0.05
0
Agosto
n=1175
0
80
100
120
140
160
Proporción
140
160
0
80
100
120
140
160
80
100
100
120
140
160
100
120
140
160
100
120
140
160
Marzo
n=2269
120
140
160
0.05
0
80
0.05
Octubre
n=669
80
Abril
n=1818
100
120
140
160
0.05
0
80
0.05
Noviembre
n=1568
0
120
0.05
Septiembre
n=544
0
100
Febrero
n=725
0.05
0
80
0.05
80
100
Mayo
n=1800
120
140
160
120
140
160
0
80
0.05
Diciembre
n=640
0
80
100
Longitud cefalotorácica (mm)
Figura 2. Proporción de talla de los machos de cangrejo dorado entre julio de 2005 y mayo de 2006.
Figure 2. Size proportions of male golden crabs between July 2005 and May 2006.
Figura 3. Diagrama qq-plot de a) la proporción de capura a la talla, y b) histograma de los residuales del modelo de crecimiento ajustado a la información de las capturas de machos de cangrejo dorado.
Figure 3. QQ-plot diagram of the a) size-at-catch proportions and b) histogram of the residuals from the growth model fit
to the catch data for male golden crabs.
320
0.05
0.05
Julio
Enero
0
0
73
87
99
110 119 127 133 139
73
Agosto
99
110
119 127 133 139
99
110
119 127 133 139
99
110
119 127 133 139
99
110
119 127 133 139
99
110
119 127 133 139
Febrero
0
0
73
87
99
110 119 127 133 139
73
87
0.05
0.05
Septiembre
Proporción
87
0.05
0.05
Marzo
0
0
73
87
99
110 119 127 133 139
73
87
0.05
0.05
Octubre
Abril
0
0
73
87
99
110 119 127 133 139
73
87
0.05
0.05
Noviembre
Mayo
0
0
73
87
99
110 119 127 133 139
73
87
0.05
Diciembre
0
73
87
99
110 119 127 133 139
Longitud cefalotorácica (mm)
Figura 4. Ajuste del modelo de crecimiento a las composiciones modales identificadas en las proporciones de tallas de las
capturas de machos de cangrejo dorado. Las líneas verticales indican la longitud modal por grupo de edad.
Figure 4. Fitting of the growth model to the modal compositions identified in the size-at-catch proportions of male golden
crabs. The vertical lines indicate the modal length per age group.
dad (20 años), y que la talla asintótica alcanzaría un
valor L∞= 178,0 mm de Lc (Tabla 2). Este valor es
significativamente mayor al promedio de los ejemplares mayores usado como penalización, lo cual desde
una perspectiva bayesiana, significa que los datos
empleados contienen información efectiva relacionada
con el crecimiento del cangrejo dorado.
Otro parámetro de interés corresponde a L1, que es la
talla media del primer grupo de edad estimado en 73,4
mm de Lc y que en la práctica no es observado en la
pesquería, sino el que le precede y estimado en 87,3
mm de Lc. Esto hace suponer que en la práctica, los
grupos de edad que cubren el rango de tamaño en las
capturas no son más de siete. El hecho que se estimen
parámetros de composiciones modales (edades) que
no están representadas en las composiciones de tallas
de las capturas, indica que la edad de reclutamiento a
la pesquería es mayor a 1 año de edad, o mejor dicho,
que la pesquería se sustenta en individuos adultos.
Tabla 2. Parámetros de crecimiento del cangrejo dorado.
Entre paréntesis se entrega el error estándar de las estimaciones.
Table 2. Growth parameters of golden crabs. The standard error of the estimate is given in parentheses.
L∞ (mm)
k (año-1)
L1 (mm)
CV
t0 (años)
178,04
(7,756)
0,143
(0,019)
73,440
(1,950)
0,056
(0,002)
0,25
El modelo no considera de manera explícita la dinámica de sobrevivencia entre cohortes y meses, sino
supone que la importancia relativa de cada grupo de
edad en las composiciones modales de tallas es independiente y está sujeta a error de observación (e.g.,
muestreo) y/o proceso (e.g., migración edadespecífica).
321
Para la asignación de los grupos de edad, en primer
lugar se calcularon las tallas modales anteriores a L1
mediante la ec. 1, pero en forma retrospectiva. La
mínima talla no-negativa fue estimada en 17,5 mm de
Lc (Tabla 3) y asignada a individuos del grupo de
edad 0. Las restantes edades fueron asignadas de manera cronológica hasta un máximo de 20 años, edad a
la cual la talla media alcanza el 95% de su longitud
asintótica (longevidad media). De igual forma, asignada la edad y conocida la talla media, el valor de t0
fue 0,253 años. De acuerdo con estos resultados, la
pesquería del cangrejo dorado estaría compuesta principalmente por individuos entre 4 y 10 años de vida
(Tabla 3, Fig. 5). Las ecuaciones de crecimiento de
von Bertanlanffy en longitud y en peso en los machos
de C. chilensis quedan definidas como:
L a ( mm ) = 178,04 ( 1 − e−0 ,14 ( a −0 ,25 ) )
W a ( g ) = 3383 ( 1 − e −0 ,14 ( a −0 ,25 ) )3,06
Mortalidad natural (M) y talla crítica (Lcrit)
La mortalidad natural fue inferida a partir de estimadores bioanalógicos y se supuso que la manipulación y
devolución de ejemplares al mar bajo la talla de referencia para ser considerados como ejemplares comerciales no son causa de mortalidad adicional. El resultado de estos indican que tres de los cinco métodos
propuestos satisfacen la restricción de plausibilidad
dado por la relación 1,5 < M/k < 2,5 (Beverton & Holt,
1959). Estos métodos correspondieron a los propuestos por Beverton & Holt (1956), Alagaraja (1984) y
Alverson & Carney (1975), los cuales entregaron valores de mortalidad natural entre 0,21 y 0,36 año-1, con
un promedio de M = 0,27 año-1 (Tabla 4), que equivale a una sobrevivencia natural anual del 76%.
En este mismo análisis, la pendiente de la curva de
captura acumulada en la temporada entregó estimados
muy elevados para ser considerados como “proxy” de
mortalidad natural, lo cual se debería probablemente a
la influencia que ha ejercido la actividad extractiva
sobre la estructura de la población o procesos de desreclutamientos de los más grandes por migración ontogenética. La competencia por acceso a las trampas
favorece a los individuos más grandes de la población
(Miller & Addison, 1995), pero en ningún caso afecta
los estimados de mortalidad que se basan precisamente en la longevidad, madurez y/o abundancia relativa a
la talla en los individuos más longevos.
Por su parte, la estimación de la talla crítica fue derivada siguiendo el perfil de los cambios en biomasa
individual en relación a la talla (Fig. 6). Los resultados
indican que la talla crítica es alcanzada a los 110 mm
de Lc, equivalente a seis años de vida, la cual es muy
Tabla 3. Longitud cefalotorácica media y edad teóricas
en machos de cangrejo dorado.
Table 3. Average theoretical cephalothoracic length and
age for male golden crabs.
Edad (años)
Lc (mm)
L/L∞ (%)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
17,45
38,84
57,37
73,44
87,37
99,44
109,91
118,98
126,84
133,66
139,57
144,69
149,13
152,98
156,32
159,21
161,72
163,89
165,78
167,41
168,82
10
22
32
41
49
56
62
67
71
75
78
81
84
86
88
89
91
92
93
94
95
Retro-cálculo
Estimadas
Proyectadas
cercana a la edad de primera captura obtenida en la
pesquería, que correspondería a individuos entre seis y
siete años (114 mm de Lc).
Figura 5. Modelo de crecimiento en machos de cangrejo
dorado, en el que se indica el rango de edad presente en
la pesquería.
Figure 5. Growth model for male golden crabs, indicating the age range present in the fishery.
322
Tabla 4. Estimación de la mortalidad natural en machos
de cangrejo dorado mediante el empleo de diferentes
métodos bioanalógicos.
Table 4. Natural mortality in male golden crabs, estimated by different bio-analogical methods.
M
M/k
Curva captura (Z)
0,48
3,36
Taylor
0,14
0,99
Beverton & Holt*
0,23
1,59
Alverson & Carney(*)
0,36
2,50
Alagaraja*
0,21
1,46
M promedio
0,27
(*) seleccionadas
Evaluación de la población
Conocido los parámetros de crecimiento y mortalidad,
el análisis en condiciones de equilibrio permitió conocer las relaciones teóricas entre la longitud cefalotorácica promedio de los ejemplares completamente reclutados a la pesquería (> 114 mm de Lc) y los niveles de
reducción de la biomasa virginal. Cabe señalar que los
ejemplares de tallas inferiores a 114 mm de Lc son
devueltos al mar y por ende considera que la selección
de la fracción bajo esa longitud es nula.
Los resultados del análisis de equilibrio generaron
una curva que relaciona la talla media de los individuos mayores a 114 mm de Lc ( L cr ) con la reducción
teórica de la biomasa virginal Bo. Se estima que la
Lcr en condiciones virginales corresponde a 129 mm
de Lc, que equivale al valor de la abscisa cuando la
razón B/Bo es igual a 100% (Fig. 7). Por su parte, los
muestreos de tallas de las capturas indican que la
Figura 6. Curva de biomasa individual por recluta respecto a la talla en machos de cangrejo dorado.
Figure 6. Individual biomass curve per recruit with respect to the size of male golden crabs.
Lcr es de 128 mm de Lc, lo que ubica a la población
explotable en un 82% de la población virginal (Fig.
8,Tabla 5). Esto corresponde a un valor de mortalidad
por pesca en torno a F = 0,05, que es inferior a Puntos
Biológicos de Referencia como es F40% = 0,34 (Mace,
1994) o F = 0,5 M sugerido por Gulland (1971) para
poblaciones vírgenes. La reducción relativa de la biomasa desovante virginal ha sido empleada para definir
puntos biológicos de referencia en muchas pesquerías.
Varios estudios (Clark, 1991; Francis, 1993; Thompson, 1993; Mace, 1994) sugieren que se pueden producir rendimientos promedios equivalentes al Máximo
Rendimiento Sostenido cuando la población se encuentra en el rango 0,3-0,5 de la condición virginal, y
que muchas pesquerías no pueden generar producción
sostenida si la reducción se ubica bajo 0,2 de Bo.
En este sentido, una reducción de la población virginal a un 40% de Bo significa registrar en la pesque-
Figura 7. a) Relación teórica entre la biomasa de largo plazo y la mortalidad por pesca, y b) relación teórica entre la talla
media de completo reclutamiento (Lcr) y la reducción de biomasa virginal en machos de cangrejo dorado.
Figure 7. a) Theoretical relationships between long-term biomass and fishing mortality, and b) between the average size
of complete recruitment (Lcr) and the reduction of virginal biomass in male golden crabs.
Figura 8. Relación teórica entre la mortalidad por pesca
y la talla media de completo reclutamiento (Lcr) en machos de cangrejo dorado.
Figure 8. Theoretical relationship between fishing mortality and the average size of complete recruitment (Lcr)
in male golden crabs.
ría una L cr de 118 mm de Lc y en el caso de F = 0,5
M una longitud L cr de 123 mm de Lc (Tabla 5). Como estos valores son inferiores a la talla L cr actual, se
deduce que este recurso podría soportar un incremento
moderado de mortalidad por pesca sin mayor detrimento de la población, teniéndose como referentes
que no se exceda el valor de referencia dado por F40%
o que la talla L cr no caiga bajo los 118 mm de Lc. Lo
anterior se consigue incrementando en tres veces los
desembarques actuales.
Finalmente, el criterio de explotación bioeconómico F0,1 (Gulland, 1983), que corresponde al
valor de F donde la pendiente del rendimiento por
recluta es igual al 10% de la pendiente original (Fig.
9), fue estimado en F0,1 = 0,35 y es similar al criterio
F40% anteriormente señalado. Esto indica que no solo
el mejor beneficio económico se lograría aumentando
Tabla 5. Mortalidad por pesca, rendimiento por recluta,
reducción de la biomasa virginal y talla media de completo reclutamiento en machos de cangrejo dorado.
Table 5. Fishing mortality, yield per recruit, virginal
biomass reduction, and full recruited mean length in male
golden crabs.
F (año-1)
Y (g)
B/Bo
Lcr (mm)
Fcr
0,050
197
84%
128
F = 0,5*M
0,135
390
66%
123
F40%
0,340
569
40%
119
F0.1
0,350
574
45%
118
323
Figura 9. Relación teórica entre la mortalidad por pesca
con el rendimiento por recluta (línea gruesa) y su variación marginal (línea delgada) respecto de la mortalidad
por pesca en machos de cangrejo dorado. En líneas segmentadas se indica el valor del 10% de la pendiente en el
origen.
Figure 9. Theoretical relationship between fishing mortality with the yield per recruit (thick line) and the marginal variation (thin line) with respect to fishing mortality in male golden crabs. The segmented lines indicate
the 10% value of the initial slope.
la mortalidad por pesca a este nivel, sino que dicho
aumento no comprometería niveles biológicos sustentables de explotación en este recurso.
DISCUSIÓN
El monitoreo de las capturas del cangrejo dorado,
permitió realizar exclusivamente el análisis de los
machos, dado que este sexo representa más del 98%
las capturas, integrando mayor cantidad de información a la que se contaba previamente. Se determinó
que el cangrejo dorado es un recurso de mediana longevidad, cuya máxima expectativa de vida es de alrededor de 20 años y que la pesquería estaría compuesta
por individuos de 4 a 10 años de edad. Por otra parte,
se estableció que tanto los parámetros de crecimiento
como el valor de mortalidad natural resultaron mayores a los estimados por Arana (2000) (L∞= 150 mm; k
= 0,1 año-1; M = 0,15 año-1), diferencia que se estima
estrechamente ligada a la mayor fuente de datos ahora
disponible. Cabe mencionar que por lo general las
estructuras de tallas o edades de ejemplares muy longevos tienden a ser simétricas, unimodales y muy
estables en el tiempo, situación que en este caso no
ocurrió.
En general, la literatura disponible sobre crecimiento en el grupo Geryonidae es escasa a nivel mun-
324
dial, aunque se postula que estos animales requerirían
de 15 o más mudas para alcanzar la talla máxima
(Haefner, 1978). Así, mediante estudios de marcaje
realizados en Chaceon (Geryon) quinquedens de Nueva Inglaterra se ha determinado que estos cangrejos
presentan un crecimiento lento y que la pesquería esta
compuesta por individuos viejos, de seis o más años
(Lux et al., 1982). Igualmente, Van Heukelem et al.
(1983) señalan que los ejemplares de esta misma especie ingresan a la pesquería realizada frente a la costa
Atlántica de los Estados Unidos cuanto tienen alrededor de seis años de vida. Un resultado semejante encuentra Melville-Smith (1989) en Chaceon (Geyon)
maritae de Sud Africa/Namibia, quien mediante el
desarrollo de un modelo hipotético, establece que esta
especie puede ser explotada a partir de los seis años de
vida, valores que son similares a los resultados alcanzados en el presente estudio.
Durante los primeros siete años de vida el cangrejo
dorado aumenta su tamaño a tasas crecientes, para
luego invertir este patrón de crecimiento a tasas decrecientes (Fig. 4). Esto último podría encontrarse relacionado con el proceso de madurez sexual, en el cual
parte importante de la energía empleada en el desarrollo corporal es orientada al proceso reproductivo y por
ende la reducción en la tasa de crecimiento. En este
sentido y de acuerdo con Charnov (1993) y Charnov
& Berrigan (1990), una aproximación a la talla de
primera madurez sexual se logra cuando el animal
alcanza 2/3 de la longitud asintótica, la que en este
estudio conlleva a una estimación de 118 mm de Lc.
De acuerdo con Guerrero & Arana (2008), la talla de
primera madurez sexual (TMS50%) es alcanzada en los
machos a los 109 mm de Lc (equivalente a 125 mm de
ancho cefalotorácico), que correspondería a individuos
entre seis y siete años. Un resultado similar se obtiene
cuando se evalúa el cambio de inflexión en el incremento marginal en el peso respecto de la edad. Sin
perjuicio de lo anterior, cabe destacar que la competencia talla-específica en las trampas limitaría la presencia de ejemplares pequeños y con ello la talla del
primer grupo de edad.
La talla crítica del recurso estimada en 110 mm de
Lc correspondería a una edad de seis años, la cual es
ligeramente inferior a la talla de primera captura en
torno a los 114 mm de Lc y ligeramente superior a la
TMS50%, situación que además permite concluir que la
explotación respecto al aprovechamiento somático del
recurso es cercana a lo óptimo, pudiéndose incluso
mejorar el rendimiento si esta talla se disminuye al
valor de la talla crítica.
De acuerdo con Beverton & Holt (1959), la mortalidad natural y el coeficiente de crecimiento k se rela-
cionan en una razón que va de 1,5 a 2,5. En el presente
estudio, dicha razón fue estimada en M/k=1,88, que
resulta consistente con el rango antes mencionado. La
estimación de la mortalidad natural se relaciona con la
longevidad y puede ser errónea si los individuos más
longevos de una población virginal no están debidamente representados en los muestreos. En el análisis
esto no fue problema, debido a que existe una dominancia de ejemplares de gran talla producto de la probable competencia talla-específica por acceso a las
trampas (Miller & Addison, 1995), lo cual provoca
además que la proporción de ejemplares de menor
tamaño esté sub-representada.
Teniendo como resultado las fluctuaciones que han
presentado las distribuciones de frecuencias de tallas
mensuales entre julio 2005 y mayo 2006, la reducción
de los ejemplares de mayor tamaño respecto a lo observado los primeros meses de pesca podría ser interpretado como un probable proceso de migración tallaespecífica. Otra posible explicación estaría en la fuerte
conducta territorial y dominancia de los ejemplares
más grandes sobre el resto de la población (Miller,
1989; Miller & Addison, 1995). De acuerdo con ello,
las primeras trampas caladas capturarían los individuos más grandes y longevos, lo que posteriormente
debiera generar mayor espacio y menor competencia
para los más jóvenes. Esto explicaría la reducción de
la talla promedio y posiblemente el aumento de los
rendimientos debido a la mayor abundanciade los
ejemplares más pequeños. Si bien no se descarta el
impacto de la pesca, se estima que si tales variaciones
en los tamaños promedio son explicadas por las causas
anteriormente mencionadas, se trataría entonces de
una población muy pequeña susceptible a la sobrepesca, lo que es incompatible con los buenos rendimientos hasta ahora obtenidos. Sin embargo, dado lo reciente del conocimiento de este recurso, resulta conveniente realizar nuevos estudios que permitan recopilar más antecedentes en relación a su etología y dinámica poblacional, para evaluar y corroborar las hipótesis formuladas.
Recientemente, FAO (2008) denominó al cangrejo
del género Chaceon como recurso de aguas profundas,
caracterizado como especie de maduración tardía,
lento crecimiento, alta longevidad, baja mortalidad
natural, reclutamientos intermitentes y adultos que no
desovan todos los años, calificación que ya había sido
dada por Elner et al. (1987) una década antes. Por su
parte, Chute (2006) indica que se trata de un recurso
frágil, que puede ser fácilmente sobreexplotado, y si
esto ocurre es de difícil recuperación, lo que genera
especial precautoriedad en cuanto a posibles incrementos en los niveles de explotación.
Weinberg & Keith (2003) entregan referencialmente una aproximación talla-estructurada para evaluar la
población del Chaceon quinquedens en el Atlántico
noroeste, lo cual exige un mayor requerimiento de
información de la que se dispone. No obstante, en el
análisis indirecto de la condición de explotación del
cangrejo dorado se logró establecer que la población
se ubicaría en torno al 82% de su condición virginal,
lo cual parece conservativo y permitiría elevar la presión de pesca si se quisiera reducir la población si se
desea alcanzar un objetivo del 40%. Esto significa
disminuir la talla promedio de 128 mm de Lc registrado en las capturas de la temporada 2005/06 a una talla
de 118 mm de Lc. Al respecto, Serchuk (1977) determinó una talla de primera captura de 114 mm de Lc
sobre la base de un estimado de M = 0,2, valores que
se comparan adecuadamente con los reportados en
este trabajo. Para lograr la conservación de la biomasa
según se propone, se genera igualmente un nivel de
mortalidad similar al óptimo bio-económico dado por
el criterio F0.1 de Gulland (1983). Sin embargo, en
términos de costo, una reducción armónica de la población implicaría elevar significativamente el esfuerzo de pesca actualmente ejercido, y lograr un aumento
en el rendimiento equivalente a tres veces el actual.
La situación actual de explotación parece ser adecuada respecto de los puntos biológicos de referencia
deducidos en el presente trabajo. Esto se ha debido al
establecimiento local de una talla de comercialización
aproximada de 114 mm de Lc, que es cercana a la talla
en la cual la biomasa por recluta es máxima junto al
despliegue de un bajo nivel de esfuerzo. En efecto, son
dos los puntos biológicos de referencia que debieran
ser considerados para generar una explotación sostenible en el tiempo: una talla de primera captura mayor
o igual a la talla crítica estimada en 110 mm de Lc, y
mantener una talla promedio de las capturas por sobre
los 118 mm de Lc, talla que en el largo plazo corresponde a una reducción de biomasa del 40% respecto
de la biomasa virgen. Mientras estos indicadores sean
asegurados, la explotación de este cangrejo sería biológicamente adecuada y sostenible en el tiempo.
AGRADECIMIENTOS
Los autores agradecen a los Sres. Mauricio Ahumada
y Pedro Apablaza la supervisión de los muestreos en
terreno y a los patrones de los botes que participaron
en el monitoreo de la pesquería, Sres. Pedro Chamorro, Mario Llanquín y Danilo Rodríguez.
325
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S.D. Sulkin. 1983. Growth of Geryon quinquedens
(Brachyura: Geryonidae) juveniles in the laboratory.
US Fish. Bull., 81(4): 903-905.
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quinquedens) in the northwest Atlantic Ocean. Crustaceana, 76(7): 819-833.
Lat. Am. J. Aquat. Res., 37(3): 327-346, 2009
Brazilian deep-sea shrimp fishery
Research Article
The deep-sea shrimp fishery off Brazil (Decapoda: Aristeidae):
development and present status
Rodrigo Dallagnolo1, José Angel Alvarez Perez1, Paulo Ricardo Pezzuto1 & Roberto Wahrlich1
1
Universidade do Vale do Itajaí, Centro de Ciências Tecnológicas da Terra e do Mar
Rua Uruguai 458, CEP 88.302-202, Itajaí, SC, Brazil
ABSTRACT. The development of a deep-sea fishery for aristeid shrimps off Brazil is reviewed from its early
days in 2002. Descriptive data were collected by observers on board 75 directed fishing trips conducted in the
study period, with a total of over 15,000 monitored trawls. An incipient fishing phase took place between November 2000 and October 2002, when aristeid shrimps were occasionally reported in the bycatch of operations
mostly targeting the Argentine hake (Merluccius hubbsi). After that, a directed fishery was established for
these resources. All nine vessels involved in this fishery (one national and eight chartered) concentrated on 11
limited grounds between 700 and 800 m deep and 18ºS and 34ºS. The main species caught between November
2002 and May 2007 was the “carabinero” Aristaeopsis edwardsiana (456,710 kg), followed by the “moruno”
Aristaeomorpha foliacea (121,497 kg), and then the “alistado” Aristeus antillensis (27,919 kg). The trawlers
operate in conjunction, such that the total area of each fishing ground was swept at least twice. This harvest
pattern substantially reduced “carabinero” catch rates from 14 kg hour-1 in the first sampled trimester to 4 kg
hour-1 in the last. Despite the inferred biomass reduction of this species, the fishery has continued without a
formal management plan.
Keywords: trawl fishery, deep-water shrimps, Aristeidae, Brazil.
La pesquería de gambas de profundidad en Brasil (Decapoda: Aristeidae):
desarrollo y estado actual
RESUMEN. Se revisa el desarrollo de una pesquería en aguas profundas dirigida a gambas aristeideas en Brasil. Desde su inicio, en 2002, los datos descriptivos fueron obtenidos por observadores a bordo de 75 viajes de
pesca realizadas en ese período que resultaron en más de 15.000 arrastres monitoreados. Una fase incipiente de
la pesquería se estableció entre noviembre de 2000 y octubre de 2002, cuando gambas aristeideas fueron registradas en la captura accidental de operaciones de pesca dirigidas principalmente a la merluza-argentina (Merluccius hubbsi). A ésta sobrevino una fase dirigida en que participaron nueve arrastreros (uno nacional y ocho
arrendados). Estos buques concentraron sus operaciones en 11 fondos de pesca angostos entre 700 y 800 m de
profundidad y los paralelos 18ºS y 34ºS. Las principales especies capturadas entre noviembre de 2002 y mayo
de 2007 fueron el “carabinero” Aristaeopsis edwardsiana (456,710 kg), seguido del “moruno” Aristaeomorpha foliacea (121,497 kg), y el “alistado” Aristeus antillensis (27,919 kg). Los arrastreros operaran de
forma agregada y esto hace que el área total de cada zona de pesca haya sido arrastrada al menos dos veces.
Este patrón de explotación ha producido reducciones substanciales en las tasas de captura del “carabinero” que
varió de 14 kg hora-1 en el primer trimestre de monitoreo a 4 kg hora-1 en el último. A pesar de la aparente reducción de biomasa de esta especie, la pesquería ha continuado sin un plan formal de manejo.
Palabras clave: pesca de arrastre, gambas de aguas profundas, Aristeidae, Brasil.
________________________
Corresponding author: Rodrigo Dallagnolo ([email protected])
327
328
INTRODUCTION
The recent development of deep-water fisheries off
Brazil has been strongly influenced by a foreign vessel-chartering program implemented by the Brazilian
government in 1998. From 2000 onwards, large vessels operating gillnets, longlines, trawls, and traps
occupied virtually unexplored areas of the continental
slope and established unprecedented fishing regimes
on shellfish and finfish species, including deep-sea
crabs (Chaceon notialis and C. ramosae), the argentine shortfin squid (Illex argentinus), the monkfish
(Lophius gastrophysus), the Argentine hake (Merluccius hubbsi), and others (Perez et al., 2003). Because
these chartered operations were intensely monitored
by observers and VMS (satellite vessel monitoring
systems) as part of their legal obligations, a large
amount of fishing and biological data was made available and used in the elaboration of preliminary stock
assessments and management plans for these resources (Perez et al., 2002a, 2002b, 2003, 2005;
Wahrlich et al., 2004; Perez & Wahrlich, 2005;
Pezzuto et al., 2006a).
As these slope fisheries intensified, principally off
the southeastern and southern sectors of the Brazilian
coast, new resources were recorded as bycatch components, most notably, the valuable deep-sea shrimps
of the family Aristeidae. In late 2002, as productive
concentrations of these resources were identified, a
new directed trawl fishery began to develop, the latest
and deepest since the onset of the chartering program
(Pezzuto et al., 2006b; Perez et al., 2009a).
This paper reviews the initial five years of the
deep-sea shrimp fishery off the Brazilian coast, adding
complementary new data on the early development
phase (2000-2004) previously described by Perez et
al. (2009a) and Pezzuto et al. (2006b). The study also
characterizes the temporal and spatial trends of the
fishery through the subsequent, more dynamic period
(2004-2007).
Fishing data were obtained from commercial operations conducted on the continental slope off the southeastern and southern sectors of the Brazilian coast,
delimited by the parallels 18ºS and 34ºS and by the
200 to 1000 m isobaths (Fig. 1). This gives a surface
area of 250,000 km², averaging 1,600 km in length
and 150 km in width and characterized by topographic
irregularities including plateaus and submarine canyons (Zembruscki, 1979).
All analyzed data originated from satellite VMS
and observers on board all chartered-fleet fishing operations conducted from October 2000 to May 2007.
Each trawl conducted by chartered vessels within this
period was described by position, date, time, and
depth (m) at deployment and retrieval, as well as the
trawl speed (knots), trawl duration (h), head rope
length (m), mesh size at cod-end (mm), and catch
composition (kg). The nationalized trawler was the
only one not subjected to the VMS or obligatory observers. Logbooks were the only source of this vessel’s catch and effort information, as provided by the
vessel skipper for nine fishing trips between 2005 and
2006.
Catch (kg), effort (trawled hour), and catch rate (kg
hour-1) variability were summarized by year and trimester, considering the different aristeid shrimp species separately. Spatial patterns of the fishing area
occupation, catch, and effort were analyzed through
VMS-generated individual positions during the fishing
trips as well as geographic trawl positions as recorded
by observers. Deployment and retrieval positions for
individual trawls conducted by the entire fleet in each
year were plotted on a cartographic basis and fishing
sectors were delimited, following Pezzuto et al.
(2006b): (a) northern, between 18º20’S and 22ºS; (b)
central, between 22ºS and 26ºS; and (c) southern,
between 26ºS and the southernmost limit of the Brazilian EEZ (Fig. 1). Fishing sectors were further subdivided into fishing grounds as delimited by the isobaths
that enclosed 80% of the fishing trawls. Each fishing
ground was referenced by a capital letter N, C, or S,
according to the sector (northern, central, or southern)
in which it was identified and followed by a number
that increased from south to north (i.e. C1 was the
southernmost fishing ground of the central fishing
sector).
The surface areas of fishing sectors and fishing
grounds were calculated by transforming latitude and
longitude coordinates into UTM and then converting
these into metric units. All geometric coordinates were
referenced on the basis of Datum SAD 1969 (South
American Datum) and their transformations considered three UTM zones that cover southeastern and
southern Brazil (UTM 22, UTM 23 and UTM 24).
RESULTS
Trawlers, gear, and trawling operations
A total of sixteen chartered trawlers operated in the
Brazilian slope waters since the year 2000. Two of
them, “Joana” and “Nuevo Apenino”, recorded
aristeid shrimps as bycatch components. For another
329
Figure 1. Study area in southeastern and southern Brazil, with an emphasis on the continental slope between 200 m and
1000 m depth and the latitudinal limits of the aristeid shrimp trawling operation sectors. Abbreviations refer to major
states in the study area: MG: Minas Gerais, ES: Espírito Santo, RJ: Río de Janeiro, SP: Sāo Paulo, SC: Santa Catarina,
RS: Río Grande do Sul, and PR: Paraná.
Figura 1. Área de estudio en el sureste y sur de Brasil con énfasis en el talud continental entre 200 y 1000 m de profundidad y límites latitudinales de los sectores de operación de la pesca de arrastre dirigida a las gambas aristeideas. Las abreviaturas se refieren a los estados en el área de estudio, MG: Minas Gerais, ES: Espírito Santo, RJ: Río de Janeiro, SP: Sāo
Paulo, SC: Santa Catarina, RS: Río Grande do Sul y PR: Paraná.
eight trawlers, these shrimps were the main target
species. All shrimp trawlers were longer than 30 m,
powered by approximately 1,000 HP engines, and
capable of performing fishing trips lasting over one
month (Table 1).
A variety of trawl nets were employed by these
vessels, most of them differing in head rope length,
which ranged from 45 to 95 m, and mesh size, which
ranged from 40 to 80 mm (Figs. 2a and 2b).
Excluding those fishing operations where deep-sea
shrimps were considered to be by-catch, a total of 75
fishing trips, around 15,000 trawls, and over 63,000
trawled hours were focused on aristeid shrimps off
southeastern and southern Brazil from 2002 to 2007
(Table 1). Trawl velocity ranged between 2 and 3
knots, although faster (4.0- 4.5 knots) and slower (under 2.0 knots) trawls were also recorded (Fig. 3a). The
duration of trawls was normally distributed around a
mean value of 4.06 h ( ± 0.007 SE) (Fig. 3b). The
product of both variables (trawl velocity and duration)
allowed us to estimate that each trawl swept an average linear extension of approximately 21 km, with
maximum values of 73 km (Fig. 3c). Wing spread was
estimated as approximately half of the head rope
length as proposed by Sparre & Venema (1997). This
measure, when multiplied by the trawl length values,
indicated that each trawl swept a mean surface area of
0.73 km² (Fig. 3d). However, this surface frequently
surpassed 1 km² and reached 2.3 km² in extreme cases.
Catch composition
Altogether, these trawlers caught approximately 600
ton of deep-sea shrimps. The “carabinero” shrimp
(Aristaeopsis edwardsiana) was the most abundant in
the catches, followed by the “moruno” shrimp (Aristaeomorpha foliacea) and finally the “alistado” shrimp
(Aristeus antillensis) (Table 2). Catches of all three
species increased steadily until 2005, a trend also observed in the total effort as expressed either in number
of trawls or trawled hours. In 2006, the fishing effort
decreased around 26% (trawled hours) and 24%
(number of trawls), coinciding with a 45% and 66%
decrease in catches of “carabinero” and “alistado”
shrimps and a 21% increase in “moruno” shrimp
catches.
Retained and commercialized bycatch were mainly
the deep-sea crab Chaceon spp. (128,950 kg), the
Argentine hake Merluccius hubbsi (71,426 kg), the
gulf hake Urophycis cirrata (25,076 kg), the monkfish
Lophius gastrophysus (20,305 kg), and the Argentine
330
Table 1. Technical characteristics of chartered trawlers and fishing operations that reported catches of aristeid shrimps (targeted and non-targeted) off the Brazilian coast from 2000 to 2007. Total number of trips, tows, and trawled hours include only fishing trips conducted during the “targeting phase” (i.e. excluding
all trips by the vessels “Joana” and “Nuevo Apenino” and fishing trips of the vessels “Mar Maria” and “Costa Grande”, which were targeting demersal fishes
on the upper slope).
Tabla 1. Características técnicas de los arrastreros arrendados y de las operaciones de pesca con capturas de gambas aristeideas (pescas dirigidas y no dirigidas
a estas especies) en la costa de Brasil entre 2000 y 2007. El número total de viajes, arrastres y horas de arrastre incluye solamente operaciones realizadas durante la “fase dirigida” (i.e. excluye todas los viajes de los buques “Joana” y “Nuevo Apenino”, y los viajes de los buques “Mar María” y “Costa Grande” que
fueron dirigidos a peces demersales del talud superior).
Total length
(m)
GT
Main engine
(Hp)
Trips
(n)
Tows
(n)
Trawling
hours
São Tomé and Príncipe
60.0
890
1.700
26/10/2000
22/01/2001
2
300
1,073.2
Nuevo Apenino
Spain
33.0
308
540
17/09/2001
28/07/2002
9
932
3,474.7
Costa Grande
Spain
30.0
170
800
30/10/2002
29/07/2003
5
1,029
4,092.9
TB1
Mauritania
37.3
276
1.218
20/12/2004
10/09/2005
2
195
867.5
Kayar
Senegal
29.0
252
650
09/11/2004
18/09/2005
6
887
3,828.7
Lago Castiñeras
Spain
36.4
354
1.200
01/10/2004
03/11/2005
5
1,200
4,904.0
Favaios
Portugal
34.0
920
900
04/08/2004
26/09/2006
10
2,354
9,861.5
Nationalized
Brazil
31.1
---
870
05/09/2005
10/12/2006
9
1,521
6,003.7
Albamar
Spain
38.0
325
1.350
31/08/2004
29/05/2007
16
3,587
13,852.2
Mar Maria
Spain
38.4
271
1.200
28/08/2002
In operation
22
4,828
19,976.8
75
15,601
63,387.3
Vessel
Origin
Joana
Total
Operations
Start
End
331
Figure 2. Distribution of the a) head rope length and b) codend mesh size used in the fishing nets for the capture of aristeid shrimps off Brazil between November 2002 and May 2007. The vessels are identified as: ALB (Albamar). CGR
(Costa Grande), FAV (Favaios), KAY (Kayar), LCAST (Lago Castiñeras), MMA (Mar Maria), NOE (Noé), and TB1
(TB1). The box in the middle indicates the quartiles of the distribution and the median (horizontal line). The “whiskers”
show the largest/smallest observations that fall within a distance determined to be 1.5 times the length of the box.
Figura 2. Distribución de a) las dimensiones de la relinga y b) de la malla del copo de la red utilizados en las redes de
arrastre para la captura de gambas aristeideas en la costa de Brasil entre noviembre de 2002 y mayo de 2007. Se identifican los buques por las abreviaciones ALB (Albamar), CGR (Costa Grande), FAV (Favaios), KAY (Kayar), LCAST (Lago Castiñeras), MMA (Mar Maria), NOE (Noé) e TB1 (TB1). La “caja” central indica los quartiles de la distribución y la
mediana (línea horizontal). Las lineas “wiskers” representan las mayores/ menores observaciones dentro de un rango
definido como 1,5 veces el largo de la “caja”.
shortfin squid Illex argentinus (49,887 kg) (Table 2).
In addition, catches included a variety of discarded
shellfish and finfish species typical of the lower slope.
Although a comprehensive qualitative and quantitative
analysis of discards has not been completed, the preliminary identification of specimens collected by observers included bonefishes of the family Synaphobranchidae, Macrouridae, Trachichtidae, Berycidae,
Astronestidae, Oreosomatidae, Ipnopidae, Alocephalidae, Ophidiidae, and others. Invertebrates have also
been frequently reported and collected, including
deep-sea corals such as Flabellum cf. alabastrum
(Pires, 2007).
(366.9 m ± 6.3 SE) and targeting mainly monkfish and
hake concentrations (Fig. 4c) conducted exploratory
trawls in areas deeper than 500 m on two occasions,
resulting in new catches (177.3 kg) of aristeid
shrimps, particularly in the vicinity of the 700 m isobath (Fig. 4d, Table 3). Also in 2002, the trawler
“Nuevo Apenino”, fishing for hake off the coasts of
São Paulo and Rio de Janeiro states (Fig. 4e), conducted 27 trawls in areas deeper than 500 m; most of
these produced positive catches of “carabinero”
shrimps (Fig. 4f). These were the largest catches recorded during the early development phase (676.67
kg) and also the highest catch rates reported until then
(8.9 kg hour-1 ± 2.5 SE) (Table 3).
Fishery history
Further concentrations of “carabinero” and “alistado” shrimps were also found in exploratory fishing
conducted by the trawler “Mar Maria” in the northern
sector of the Brazilian coast, off the coasts of the
states of Amapá and Pará, between 1°-6°N and 45°51°W (Asano-Filho et al., 2005; Pezzuto et al., 2006b;
Perez et al., 2009a) (Table 3). Whereas all aristeid
shrimp catches reported above were minor components of the total catches, they were profitable enough
to stimulate a new fishing phase, the deepest
The Portuguese vessel “Joana” was the first trawler to
operate under the chartering program and reported the
first catches of “alistado” shrimps in nine out of 300
trawls conducted in late 2000 – early 2001 (Figs. 4a
and 4b). One of them at occurred at 32°S (300 m
depth; 2.1 kg) and the others were recorded off the
coast of the states of São Paulo and Rio de Janeiro at
23°S (384-460 m depth; 18.9 kg) (Table 3). In 2002,
the trawler “Costa Grande” operating on slope areas
332
Figure 3. Fishing strategies adopted by the chartered trawlers for the aristeid shrimp fishery off Brazil between November
2002 and May 2007.
Figura 3. Estrategias de pesca empleadas por los arrastreros arrendados en la pesca de gambas aristeideas en la costa de
Brasil entre noviembre de 2002 y mayo de 2008.
ever recorded in the country (Pezzuto et al., 2006b;
Perez et al., 2009b). Thus, the chartered trawlers
“Costa Grande” and “Mar Maria” pioneered the fishery, targeting aristeid shrimps in 2003 with lower
slope trawling operations (Fig. 5). In the following
year, as the former vessels abandoned Brazilian waters, five new trawlers entered the fishery under the
chartering program composing, in 2003 and 2005, the
largest fleet operating simultaneously on these slope
areas. In 2006, this fleet was reduced to four units,
including a new nationalized vessel. In 2007, only the
latter vessel and “Mar Maria” maintained their operations on aristeid shrimps of Brazil (Fig. 5).
Until the end of 2004, the central (22-26ºS) sector
concentrated all the fishing effort. In 2005, the new
vessels “Favaios”, “Albamar”, “Lago Castiñeras”, and
“Kayar” started to fish in the northern (north of 22ºS)
and southern (south of 26ºS) sectors, thereby expanding the fishery to the entire latitudinal extension of the
slope off southeastern and southern Brazilian (Fig. 5).
The “carabinero” shrimp dominated the catches in
all fishing sectors and was particularly abundant in the
central sector and virtually the only species caught in
the southern sector. The “moruno” shrimp, which is
the second species in terms of total catches, was
caught predominantly in the central sector, although
catches in 2005 were considerably higher in the northern sector. The “alistado” shrimp was caught most
abundantly in the northern sector throughout the entire
fishing period (Table 4). The fishing effort was particularly concentrated in the central sector, peaking in
2005 with 2,911 trawls and 11,844 trawled hours exerted on this sector. In 2007, the effort tended to be
evenly distributed throughout the entire fishing area.
333
Table 2. Annual fishing effort and catches (kg) of aristeid shrimp and the retained bycatch species off Brazil between 2002 and 2007. Data from 2007 are partial and
include only the first semester.
Tabla 2. Esfuerzo anual de pesca y capturas (kg) de gambas aristeideas y especies de la captura accesoria en la costa de Brasil entre 2002 y 2007. Datos de 2007 son
parciales e incluyen solamente el primer semestre.
Number of Aristaeopsis Aristaeomorpha Aristeus
tows
edwardsiana
foliacea
antillensis
Chaceon
spp.
Meluccius
hubbsi
Illex
argentinus
0.0
4,584.0
35,001.5
40.0
1,786.1
5,448.0
64,680.0
4,585.4
474.9
23,380.0
23,808.9
7,837.0
1,813.6
14,292.2
143,686.8
81,585.1
14,861.4
5,489.1
30,322.0
4,090.8
0.0
2,742.3
225.0
139,901.7
6,120
182,632.9
42,568.2
15,828.4
48,437.8
3,448.0
2,910.0
10,842.0
72.0
308,841.3
18,372.3
4,608
99,325.3
51,756.4
5,365.4
18,056.5
4,735.0
39,100.0
7,267.0
340.0
226,730.1
2007
3,193.8
856
19,865.0
7,426.0
762.0
4,170.0
342.0
0.0
626.0
0.0
33,491.0
Total
63,367.3
15,601
455,357.8
121,497.4
27,919.8
128,950.3
71,426.2
49,887.0
25,077.0
20,305.21
917,258.9
Year
Trawling
hours
2002
935
238
13,021.0
0.0
2003
6,183.4
1,503
58,928.5
2004
9,737.3
2,276
2005
24,945.6
2006
Lophius
Total catch
Urophycis
cirrata
gastrophysus
(kg)
334
Figure 4. Geographic position of all fishing tows (left column) and of the fishing tows with incidental catches of aristeid
shrimp fishery (right column) conducted by the vessels Joana (a and b), Costa Grande (c and d) and Nuevo Apenino (e
and f).
Figura 4. Posición geográfica de todos los lances de pesca (columna de la izquierda) y de los lances de pesca con capturas incidentales de gambas aristeideas (columna de la derecha) realizados por los buques Joana, (a y b) Costa Grande (c y
d) y Nuevo Apenino (e y f).
335
Table 3. Summary of aristeid shrimp bycatch off Brazil between 2000 and 2002.
Tabla 3. Resumen de las capturas accesorias de gambas aristeideas en la costa de Brasil entre 2000 y 2002.
Vessel
(trips)
Fishing trip
start
Aristaeopsis
edwardsiana (kg)
Aristaeomorpha
foliacea (kg)
Total catch (kg)
Joana (1)
26/10/2000
---
2.1
143,815.0
Joana (2)
16/12/2000
---
18.9
168,136.1
Costa Grande (1)
04/04/2002
166.7
---
297,838.9
Costa Grande (2)
17/05/2002
10.6
120.0
76,761.4
Nuevo Apenino (9)
15/06/2002
676.7
---
85,347.1
Mar Maria (1)
23/08/2002
498.5
207.6
51,427.8
Fishing grounds and intensity
In all fishing sectors, the trawls tended to concentrate
on a narrow bathymetric stratum between 700 and 750
m depth (Fig. 6). An analysis of the distribution of
fishing trawls on a finer spatial resolution allowed the
definition of particular fishing grounds within the
defined sectors where fishing activity was intense.
The central sector enclosed four localized fishing
grounds intensely exploited since 2002 (Fig. 7a). The
first trawling operations targeting “carabinero” shrimp
concentrations occupied a northern fishing ground
(C3). In the following year, the fishing area extended
southwards, promoting the occupation of fishing
grounds C1 and C2. By 2005, the last fishing ground
(C4) was established in the northern extreme of this
sector (Fig. 7a).
The exploitation of the northern sector began in
2004 and was concentrated in two well-defined fishing
grounds (N2 and N4) (Fig. 7b). In the following year,
a small fishing ground was established on the western
side of the Besnard seamount, a component of the
“Vitória-Trindade” chain (N3). In 2006-2007, a last
fishing ground began to be exploited at the southern
extreme of this sector (N1) (Fig. 7b). Three fishing
grounds were exploited within the southern sector
between 2005 and 2007 (S1, S2, S3) (Fig. 7c); a major
submarine canyon separates S1 and S2.
The surface area of all the fishing grounds was limited, ranging between 125 km² and 1,227 km² (Table
5). In the central sector, the largest fishing grounds,
C2 and C3, were trawled for almost 30,000 hours in
total, accumulating nearly 45% of all fishing effort.
The entire surface area of the fishing grounds C1, C2,
and C3 was swept approximately two times. C4, the
last ground to be fished by the trawl fleet, was swept
1.5 times over nearly one year of exploration (Fig. 8a).
Most of the trawling efforts in the northern sector
were concentrated in grounds N2 and N3 (Table 5).
These grounds and N4 were fully swept at least 2.5
times, whereas N1 was swept 1.5 times. In the case of
N3, which only began to be explored after mid-2005,
the activity was much more intense than in the other
grounds; in only six months, its surface area had been
completely swept twice (Fig. 8b). In the southern sector, grounds S1 and S3 concentrated most of the trawling effort (Table 5) and had their entire surface areas
swept once (Fig. 8c). Nevertheless, these grounds
were less trawled than those of the central and northern sectors.
The largest catches of “carabinero” shrimps were
recorded in fishing grounds C2 and C3. The largest
catches of “moruno” shrimp originated from fishing
grounds C3, C4, and N1. The largest catches of “alistado” shrimp were obtained in fishing grounds N2 and
N4. In the central sector, the “carabinero” shrimp
dominated the trawlers’ catch except for the fishing
ground C4, where “moruno” shrimp catches surpassed
those of all other species (Table 5). However, an increasing proportion of the latter species was noticeable
in the catches of 2006, particularly in fishing grounds
C1, C2, and C3, as the proportion of “carabinero”
shrimp declined (Fig. 9).
In the northern sector, this trend was not observed
with the same clarity (Fig. 10). The proportion of
shrimp species in the catches from fishing ground N1
remained stable, whereas the proportion of shrimp
species alternated in the catches from fishing grounds
N2, N3, and N4 (Fig. 10).
Catch rate
The “carabinero” shrimp sustained the highest
mean catch (14 to 4.7 kg hour-1) rates throughout the
336
Figure 5. Daily fishing tows for the aristeid shrimp fishery off southeastern and southern Brazil. The first fishing day was 30 October 2002 and the last (1,673th) was
29 May 2007. Months and years are depicted over the x-axis. Each graph represents fishing operations of individual vessels denoted as: “Costa Grande” (CGR), “Mar
Maria” (MMA), “Favaios” (FAV), “Albamar” (ALB), “Lago Castiñeras” (LCAST), “Kayar” (KAY), “TB1” (TB1), and Nationalized Vessel (NV).
Figura 5. Lances de arrastre diarios realizados para la captura de las gambas aristeideas en el sureste y sur de Brasil. El primer día de pesca fue el 30 de octubre de
2002. El último día (1.673) fue el 29 de mayo de 2007. Meses y años están representados sobre el eje x. Cada gráfico representa las operaciones de buques individualizados denotados como: “Costa Grande” (CGR). “Mar Maria” (MMA). “Favaios” (FAV). “Albamar” (ALB). “Lago Castiñeras” (LCAST). “Kayar” (KAY). “TB1”
(TB1) y Barcos nacionalizados (NV).
337
Table 4. Geographic distribution of the fishing effort and catches of aristeid shrimps off Brazil between November 2002
and May 2007. Number of tows (tows); trawling hours (trawl); and catches of Aristaeopsis edwardsiana, Aristaeomorpha
foliacea and Aristeus antillensis.
Tabla 4. Distribución geográfica del esfuerzo pesquero y capturas de gambas aristeideas en la costa de Brasil entre
noviembre de 2002 y mayo de 2007. Número de arrastres (tows); horas de arrastre (trawl); capturas de Aristaeopsis edwardsiana, Aristaeomorpha foliacea y Aristeus antillensis.
Year
Operation sector
2002
2003
2004
2005
2006
2007
Total
521
2,141.2
21,317.9
5,114.6
1,652.1
2,163
8,957.7
58,300.0
15,036.1
27,191.0
869
3,126.4
19,177.9
2,030.8
19,151.3
290
907.3
6,413.0
756.0
4,552.0
3,843
15,132.6
105,208.9
22,937.5
52,546.5
1,750
7,577.6
60,267.2
374.5
13,209.2
2,901
11,844.5
89,685.9
775.9
15,316.6
2,200
9,215.4
43,300.2
3,306.6
32,178.1
274
1,081.8
5,847.0
6.0
3,134.0
8,806
36,658.9
270,678.7
4,937.9
68,423.3
1,047
4,105.9
34,637.7
8.2
60.5
1,376
5,503.8
34,141.6
26.0
121.0
292
1,204.7
7,605.0
0.0
40.0
2,728
10,862.4
76,711.5
34.2
221.5
Northern
tows (n)
trawl (h)
Aristaeopsis edwardsiana (kg)
Aristeus antillensis (kg)
Aristaeomorpha foliacea (kg)
Central
tows (n)
trawl (h)
Southern
tows (n)
trawl (h)
13
48
327.1
0.0
0.0
tows (n)
Northward trawl (h)
of
18º 20’S Aristeus antillensis (kg)
47
130.8
44.0
0.0
0.0
5
18.5
0.0
0.0
0.0
9
37.5
9.2
8.2
0.0
163
526.6
2,705.6
2.0
306.0
1,503
6,183.4
58,928.5
474.9
4,585.4
2,276
9,737.3
81,585.1
5,489.1
14,861.4
6,120
24,945.6
182,632.9
15,828.4
42,568.2
4,608
18,372.3
99,325.3
5,365.4
51,756.4
Total
tows (n)
trawl (h)
238
935
13,021
0.0
0.0
238
935
13,021
0.0
0.0
1,443
6,004.6
58,557.4
474.9
4,585.4
entire period (2004-2007) (Fig. 11). These rates
tended to decline locally and were generally higher as
the different fishing sectors were exploited for the first
time (Table 6).
Annually, mean catch rates declined steadily in all
fishing sectors. In the central sector, mean catch rates
decreased 61% between 2002 and 2007. The same was
observed in the northern sector, where mean catch
rates declined 36% from 2004 to 2006, increasing
slightly in 2007. In the southern sector, catch rates
dropped 26% in the first year of exploitation (20052006), stabilizing in 2007. “Carabinero” shrimp catch
rates also exhibited seasonal variations, peaking every
year in the fourth trimester. This pattern has been
224
713.4
2,758.8
10.2
306.0
856
3,193.8
19,865.0
762.0
7,726.0
15,601
63,367.3
455,357.9
27,919.8
121,497.3
consistently observed in the central and southern sectors and is less pronounced in the northern sector.
The catch rates for “moruno” shrimp were generally lower than those of the “carabinero” shrimp (6.3
to 0.76 kg hour-1) (Fig. 12). The annual variation of
the former, however, exhibited a contrasting pattern in
relation to the latter species i.e., it tended to increase
in the last years of deep-sea shrimp exploration. In the
central and northern sectors, the catch rates increased
327% and 835% from 2002 to 2006 (Table 6). In
2006, the “moruno” shrimp catch rates were comparable with those of the “carabinero” shrimp, unlike the
early fishery, when the latter species was significantly
more productive. Within-year catch rate variations
338
Figure 6. Distribution of individual tow depths in operations targeting aristeid shrimps off Brazil by latitudinal
sector between November 2002 and May 2007. The box
in the middle indicates quartiles of the distribution and
the median (horizontal line). The “whiskers” show the
largest/smallest observations that fall within a distance
determined to be 1.5 times the length of the box. Observations falling outside the referred limits are shown separately as individual dots.
Figura 6. Distribución de las profundidades de los lances
de pesca dirigidos a la captura de las gambas aristeideas
por sector latitudinal en la costa de Brasil entre noviembre de 2002 y mayo de 2007. La “caja” central indica los
quartiles de la distribución y la mediana (línea horizontal). Las líneas “whiskers” representan las menores/mayores observaciones dentro de un rango definido como
1,5 veces el largo de la “caja”. Observaciones fuera de
los límites referidos son representadas por separado como puntos individuales.
were clearly distinguished in the northern sector, with
peaks in the fourth trimester. In the central sector,
seasonal variations were not as clearly defined, although lower catch rates were generally obtained for
each year in the first trimester.
Catch rates of the “alistado” shrimp were, on average, the lowest among deep-sea shrimps (2.4 to 0.005
kg hour-1) (Fig. 13). In the northern sector, however,
the contribution of this species to the total aristeid
shrimp catch was significantly higher than in the central sector, where it never surpassed 1.0 kg hour-1
(Table 6). In the northern sector, catch rates decreased around 65% between 2004 and 2007. In
contrast with the other deep-sea shrimps exploited
off Brazil, no within-year cyclic variation could be
distinguished for the catch rate of “alistado”
shrimps.
Figure 7. Fishing grounds on the middle slope of the a)
central, b) north, and c) south sectors used by the chartered trawlers for the aristeid shrimp fishery off Brazil.
Figura 7. Áreas de pesca en el talud central de los sectores a) central, b) norte y c) sur utilizados por los arrastreros fletados en la captura de gambas aristeideas en la
costa de Brasil.
DISCUSSION
The descriptive analysis of the first five years of deepsea shrimp exploration off Brazil revealed general
patterns closely resembling aristeid fisheries elsewhere in the world. In French Guiana, the main fishing grounds are located between 400 and 900 m deep
and most catches occur in the second half of the year
in the vicinity of the 700 m isobath (Guéguen, 2000).
Trawl surveys conducted in that area in 1990 obtained
shrimp catch rates ranging between 13.2 and 40.6 kg
hour-1 (“carabinero”) and 0.09 and 0.74 kg hour-1 (“alistado”) (Guéguen, 1998, 2000, 2001). In the Mediterranean Sea, the “gambero rosso” (Aristaeomorpha
foliacea), known as “moruno” in Brazil, and “gamba
rosada” (Aristeus antennatus), a species similar to the
Brazilian “alistado” (Aristeus antillensis), have been
reported to concentrate at 700 m depth close to the
borders of submarine canyons. Seasonal fluctuations
339
in abundance have also been observed for both species; “gambero rosso” and “gamba rosada” are more
productive in summer and winter-spring, respectively
(Sardá, 2000). The highest catch rates of the “gambero
rosso” shrimp were obtained off the coast of Algeria
(around 12 kg hour-1), whereas “gamba rosada”
shrimps were more productive on the coast of Tunisia
(around 15 kg hour-1) (Sardà, 2000).
In other regions of the Mediterranean, catch rates
have been considerably lower. In the NW Mediterranean, for example, a “gambero rosso” shrimp fishery
was sustained for ten years (1991-2001) with catch
rates oscillating between 4.55 kg hour-1 and 7.54 kg
hour-1 (Carbonell & Azevedo, 2003). Off Brazil, deepsea shrimp operations also concentrated around the
700 m isobath and catches included the “gambero
rosso” exploited in the Mediterranean as well as the
“alistado” (Aristeus antillensis) and “carabinero”
(Aristaeopsis edwardsiana) shrimps also exploited off
French Guiana. At least the “carabinero” and
“moruno” shrimps showed seasonal concentrations in
the main fishing areas and catch rates for all species
ranged between 4.0 and 14.0 kg hour-1, within the
ranges reported for the aristeid fisheries above. Interestingly, scientific surveys conducted in 2004 in the
northern extreme of the study area (northern sector)
lead to the conclusion that these shrimps could not
sustain economic exploitation on the basis of very
similar catch rate levels obtained in most samplings
(Costa et al., 2005). Whereas these levels are indeed
remarkably lower than those generally sustained by
coastal shrimps, the high market prices of aristeid
shrimps allow a profitable commercial exploitation
even in the long-term (more than 10 years) such as
that observed in the Mediterranean fisheries (Carbonell & Azevedo, 2003).
Figure 8. Cumulative curves of the area swept daily by
the aristeid shrimp trawl fishery off Brazil. Values were
weighted by the surface of each fishing ground within the
latitudinal sectors a) south, b) central, and c) north. Vertical lines delimit the years of exploitation.
Figura 8. Curvas cumulativas de las áreas barridas diariamente por la pesca de arrastre dirigida a las gambas
aristeideas en la costa de Brasil. Los valores fueron ponderados por la superficie de cada área de pesca dentro de
los sectores latitudinales sur (a), central (b) y norte (c).
Las líneas verticales delimitan los años de explotación.
Another similar pattern found between the Brazilian aristeid shrimp fishery and those sustained elsewhere in the world is the alternation of dominant species on the fishing grounds. Off the Brazilian slope,
catches were generally dominated by the “carabinero”
shrimp. As catch rates of this species decreased, possibly as a consequence of heavy fishing, other species,
usually the “moruno”, tended to exhibit higher proportions and to replace the “carabinero” in the catches. In
the Gulf of Lion (Mediterranean Sea), the same scenario was observed on fishing grounds where the disappearance of “moruno” shrimp resulted in the increase of “alistado” shrimp in catches (Campillo, 1994
fide Cau et al., 2002), although ecological aspects
related to this pattern are unclear. But it is possible
that the species composition in the catches reflects the
natural dominance pattern of the three species in the
depth stratum exploited by the trawlers, which, in turn,
340
Table 5. Catches, fishing effort, and surface areas of the fishing grounds explored by the chartered trawlers targeting
aristeid shrimps off Brazil between November 2002 and May 2007. NA: tows conducted outside the fishing grounds and
north of 18º20’S.
Tabla 5. Capturas, esfuerzo de pesca y área de los fondos de pesca explotados por arrastreros arrendados para la pesca de
gambas aristeideas en la costa de Brasil entre noviembre 2002 y mayo 2007. NA: arrastres realizados fuera de los fondos
de pesca y al norte de 18º20’S.
Fishing
grounds
Area
(km²)
Tows
(total number)
Trawling
hours
A. edwardsiana
(kg)
A. foliacea
(kg)
A. antillensis
(kg)
S1
766.808
1,383
5,701.7
41,858.9
61.2
24.7
S2
158.873
231
766.8
5,425.8
26.6
3.5
S3
496.853
1,096
4,334.2
29,324.8
133.8
6.0
C1
349.259
1,323
5,069.7
38,974.2
1,981.9
124.0
C2
1,226.655
3,811
16,207.4
124,660.1
16,472.1
1,297.5
C3
1,040.714
2,988
12,493.1
100,077.5
27,582.7
2,819.0
C4
202.300
404
1,794.7
6,822.8
22,386.6
697.4
N1
341.585
800
2,727.2
16,274.1
25,380.5
2,155.8
N2
463.798
1,682
6,769.7
47,427.7
9,308.8
9,413.2
N3
252.857
929
4,041.4
32,076.9
15,360.3
237.8
N4
124.521
412
1,538.1
9,090.4
2,481.3
11,098.5
NA
542
1,923.0
3,344.7
321.7
42.4
Total
15,601
63,367.1
455,357.8
121,497.4
27,919.8
Table 6. Annual mean yields (kg hour-1) of Aristaeopsis edwardsiana, Aristaeomorpha foliacea, and Aristeus antillensis
obtained by chartered trawlers within each latitudinal sector. Standard errors are given between brackets.
Tabla 6. Rendimientos anuales (kg hora-1) de Aristaeopsis edwardsiana, Aristaeomorpha foliacea y Aristeus antillensis
obtenidos por arrastreros arrendados dentro de los sectores latitudinales. Valores del error estándard entre paréntesis.
Year
Central
(kg hour-1)
Northern
(kg hour-1)
Southern
(kg hour-1)
2002
14.026
( ± 0.830)
---
---
2003
9.380
( ± 0.164)
---
---
0.774
( ± 0.065)
---
0.082
( ± 0.006)
---
2004
8.130
( ± 0.116)
9.750
( ± 0.257)
---
1.743
( ± 0.088)
0.760
( ± 0.053)
0.051
( ± 0.004)
2.386
( ± 0.193)
2005
7.686
( ± 0.081)
6.468
( ± 0.087)
8.492
( ± 0.122)
1.264
( ± 0.070)
3.084
( ± 0.127)
0.062
( ± 0.005)
1.757
( ± 0.081)
2006
4.705
( ± 0.055)
6.221
( ± 0.123)
6.234
( ± 0.090)
3.269
( ± 0.180)
6.351
( ± 0.270)
0.344
( ± 0.034)
0.703
( ± 0.055)
2007
5.380
( ± 0.140)
7.076
( ± 0.211)
6.362
( ± 0.139)
3.046
( ± 0.275)
5.088
( ± 0.489)
0.005
( ± 0.003)
0.825
( ± 0.080)
Central
(kg hour-1)
0.000
Northern
(kg hour-1)
---
Central
(kg hour-1)
0.000
Northern
(kg hour-1)
---
Figure 9. Relative composition of the three species of
aristeid shrimps in annual catches obtained by operations
in the fishing grounds of the central sector, southeastern
Brazil. Data from 2007 refer to the first semester only.
Figura 9. Composición relativa de las tres especies de
gambas aristeideas en las capturas anuales obtenidas en
las áreas de pesca del sector central, sureste de Brasil.
Datos de 2007 se refieren al primer semestre.
341
Figure 10. Relative composition of the three species of
aristeid shrimps in annual catches obtained by operations
in the fishing grounds of the north sector, southeastern
Brazil. Data from 2007 refer to the first semester only.
Figura 10. Composición relativa de las tres especies de
gambas aristeideas en las capturas anuales obtenidas en
las áreas de pesca del sector norte, sureste de Brasil.
Datos de 2007 se refieren al primer semestre.
Figure 11. Mean yields (kg hour-1) and standard errors
(vertical bars) of Aristaeopsis edwardsiana for each
quarter of the trawl fishery off Brazil in the a) central
sector, b) north sector, and c) south sector.
Figura 11. Rendimientos medios (kg hora-1) y error
patrón (líneas verticales) de Aristaeopsis edwardsiana en
cada trimestre de la pesquería de arrastre en la costra de
Brasil. a) sector central, b) sector norte y c) sector sur.
342
(vertical bars) of Aristaeomorpha foliacea for each quarter of fishery off Brazil in the a) central sector and b)
north sector.
patrón (líneas verticales) de Aristaeomorpha foliacea en
cada trimestre de la pesquería de arrastre en la costa de
Brasil. a) sector central y b) sector norte.
(vertical bars) of Aristeus antillensis for each quarter of
fishery off Brazil in the a) central sector and b) north
sector.
patrón (líneas verticales) de Aristeus antillensis en cada
trimestre de la pesquería de arrastre en la costa de Brasil.
a) sector central y b) sector norte.
may be part of the potential outcome of a competition
process in the slope areas. In this process, “carabinero” shrimps might have naturally predominated the
fishing areas of Brazil, whereas “moruno” and “alistado” shrimps may have been limited to deeper or
adjacent areas not exploited by the fishery. Because
the “carabinero” attains larger sizes and matures later
in life, the species may be better fit for survival and
out-compete the others within the 700-800 m stratum.
Fishing first removes the highly vulnerable “carabinero” shrimp, opening space on the fishing grounds for
smaller and possibly faster-growing “moruno” to expand their distribution. Studies conducted by Pezzuto
& Dias (2007) revealed that the “moruno” shrimp has
a continuous, year-round reproductive pattern,
whereas the “carabinero” shrimp has defined, seasonal
reproductive activity. Such distinct reproductive
strategies may also provide evidence to support a possible dominance oscillation. Although mostly hypothetical at this point, such an interpretation is partially
supported by the results of trawling surveys conducted
in the northern sector of the study area (Serejo et al.,
2007), revealing discrete bathymetrically-defined
crustacean assemblages on the slope. Aristeid shrimps,
which occur in areas as deep as 1,800 m, seem to con
centrate in the rather narrow 500-700 m depth stratum,
as also reported in other areas of the world (Cartes &
Sardà, 1992).
Despite the biological and ecological similarities of
these resources, fishery regimes have usually been
established following different structural and motivational processes, including:
a) Long-term fisheries normally developed in combination with the seasonal availability of other
demersal resources. In French Guiana, an aristeid
fishery has been carried out for 20 years by a local
fleet of small trawlers as a seasonal alternative to
their main target, the coastal penaeid shrimp Farfantepenaeus subtilis. Catches are concentrated
between June and November, when the abundance
of F. subtilis decreases on the shelf areas and that
of the “carabinero” increases on the middle and
lower slope (Guéguen, 1998). In the Mediterranean Sea, this fishery has existed for more than 60
years, conducted by regional fleets of trawlers
generally smaller than those operating under the
chartering program in Brazilian waters. Mediterranean trawlers concentrate on aristeid shrimp as
long as their density is sustained over profitable
343
levels, switching to other valuable resources otherwise (Maynou et al., 2003; Company et al.,
2008).
b) Opportunistic exploitation as valuable bycatch
components of multispecies trawling operations.
In Portugal, small catches of aristeid shrimps are
part of a multi-specific, crustacean slope fishery
(Monteiro et al., 2001). Only in recent years has a
directed fishery for aristeid shrimp been proposed
due to its high market value and the overexploitation of traditional resources (Figueiredo et al.,
2001).
c) Planned activities considering previously assessed
local fishing potential. In Indonesian waters, a directed fishery for aristeid shrimp and other crustaceans only developed after stock assessment allowed for the definition of effort limits and maximum annual caches (Suman et al., 2006). On fishing grounds of the Ionian Sea, virginal populations of aristeid shrimps were intensely studied in
order to subsidize the development of a directed
fishery under precautionary effort limitations (Papaconstantinou & Kapiris, 2001, 2003).
None of the processes above can be directly related
to the development of the Brazilian fishery for aristeid
shrimps. In this case, the activity was induced by fishing authorities as a way of obtaining knowledge on
stock distribution and availability, fishing and processing technology, and market opportunities (Perez et al.,
2003). This process, however, was not ruled by precaution or a previous delimitation of the stock potentiality but was mostly profit-oriented, fast, uncontrolled,
and disorganized. Since its early days, an excessive
number of large vessels were allowed to concentrate
in very limited areas of the central slope, and the most
productive grounds were fully swept (once to twice) in
a very short time. The exploration of new sectors of
the Brazilian slope were only initiated as catch rates of
the “carabinero” shrimp dropped below profitable
levels in the central sector. Such exploration, however,
followed the same “clean-up” strategy and produced
similar local density reductions in the northern and
southern slope sectors. Pezzuto et al. (2006b) analyzed
this fishery between October 2002 and August 2004,
warning about the negative consequences of the kind
of fishing regime promoted by the chartered fleet.
They concluded that operating large chartered trawlers
in very restricted areas of the slope was only justifiable as long as it complemented existing information
on deep-sea shrimp concentrations with data from still
unexplored areas. In that sense, the interruption of the
entry of new vessels into the fishery was recommended, along with the establishment of a rotating
harvesting strategy that would allow the effort to
spread along the Brazilian EEZ. As demonstrated,
however, the deep-sea shrimp fishery developed off
Brazil after 2004 regardless of these recommendations. In 2007, only two vessels were operating, a
natural consequence of the major reduction of catch
rates verified in most exploited fishing areas. Although producing timely estimates for a valuable and
sustainable fishery development, this process rendered
a biologically unsafe and unsustainable scenario and
proved to be a dangerous strategy, particularly when
directed at fragile deep-sea resources. Whereas the
fishing regime established for the aristeid shrimps off
Brazil seems to be clearly incompatible with sustained
activity, its continuity under any of the patterns described elsewhere in the world will depend on severe
restrictions to the total effort and a complete plan for
biomass restoration on most productive grounds.
ACKNOWLEDGEMENTS
The authors are thankful to the Brazilian Government
(SEAP/PR/001/2003; SEAP/PR/078/2004; SEAP/PR/
064/2005; SEAP/PR/027/2007), the team of fisheries
observers, and the staff of “Grupo de Estudos
Pesqueiros” for making available information indispensable to this study.
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346
Lat. Am. J. Aquat. Res., 37(3): 347-360, 2009 Size and maturity of the Juan Fernández golden crab
347
Research Article
Size structure and sexual maturity of the golden crab (Chaceon chilensis)
exploited off Robinson Crusoe Island, Chile
1
Aurora Guerrero1 & Patricio Arana1
ABSTRACT. Golden crab (Chaceon chilensis) specimens were analyzed after being caught with traps by
artisanal fishermen off Robinson Crusoe Island, Juan Fernández Archipelago, Chile. Of the 13,027 individuals
caught between 300 and 1,000 m depth, 97.9% were male (12,754) and the rest female (273). The carapace
length (CL) of the sampled crabs was measured and, on average, the males (CL: 118.9 mm) were larger than
the females (CL: 94.3 mm). On the north side of the island, the specimens presented lower average sizes
(112.2 mm) whereas, in the remaining zones, the average carapace lengths were similar (CL: 117.1-119.5
mm). In bathymetric terms, an increasing trend was seen between average size and depth, with sizes over 123
mm CL found beginning at 750 m depth. A comparison of linear regressions between the carapace length and
chela length of males revealed physical maturity at 100 mm CL, whereas a numerical analysis showed the size
at first sexual maturity (SSM50%) to be 109 mm CL.
Keywords: golden crab, Chaceon chilensis, size distribution, maturity, Juan Fernandez Archipelago, Chile.
Estructuras de tallas y madurez en el cangrejo dorado (Chaceon chilensis)
explotado alrededor de la isla Robinson Crusoe, Chile
RESUMEN. Se analizaron ejemplares de cangrejo dorado (Chaceon chilensis) capturados mediante trampas
por pescadores artesanales en torno a la isla Robinson Crusoe del archipiélago de Juan Fernández (Chile),
entre 300 y 1.000 m de profundidad. Se midió la longitud cefalotorácica (LC) de 13.027 individuos de los
cuales 12.754 correspondieron a machos y únicamente 273 a hembras, con un claro predominio de machos
(97,9%), fueron de talla promedio superior a las hembras (118,9 y 94,3 mm de LC, respectivamente). En el
sector norte de la isla, se encontraron ejemplares con menor talla media (112,2 mm) que en las zonas restantes,
la longitud cefalotorácica media presentó valores similares (117,1 a 119,5 mm de LC). Se encontró una
tendencia creciente entre la talla media y la profundidad, registrándose a partir del estrato de 750 m tallas
promedio superiores a 123 mm de LC. Mediante la comparación de regresiones lineales entre la longitud
cefalotorácica y la longitud de la quela, en machos se estableció la talla de madurez física a los 100 mm de LC
y mediante análisis numérico la talla de primera madurez sexual (TMS50%) a los 109 mm de LC.
Palabras clave: cangrejo dorado, Chaceon chilensis, distribución de tallas, madurez, archipiélago de Juan
Fernández, Chile.
________________________
INTRODUCTION
The golden crab (Chaceon chilensis Chirino-Gálvez &
Manning, 1989) is a crustacean belonging to the family Geryonidae. This crab is distributed in the Juan
Fernández underwater mountain range and off San
Félix and San Ambrosio islands (Retamal, 1981;
Chirino-Gálvez & Manning, 1989). Occasionally, this
species has been detected off the central coast of Chile
(Báez & Andrade, 1977; Andrade & Báez, 1980;
Andrade, 1985, 1987). Moreover, Parin et al. (1997)
reported the presence of a geryonid in the Nazca un-
348
derwater mountain range that could correspond to C.
chilensis; nonetheless, this finding has not been ratified. Golden crabs are generally distributed to 2,000 m
depth (Dawson & Webber, 1991). Around Robinson
Crusoe and Santa Clara islands, however, they have
been found inhabiting muddy-sandy bottoms (Arana
& Vega, 2000) from 100 m to 1000 m, the maximum
depth explored off these islands (Arana, 2000a). Fishing activities are normally carried out between 450
and 550 m depth, where these crustaceans are most
abundant (Arana et al., 2006).
As a result of the exploratory fishing campaigns
carried out (by the Pontificia Universidad Católica of
Valparaíso) around Robinson Crusoe and Santa Clara
islands in 1996 and 1997 (Arana, 2000a, 200b; Arana
& Vega, 2000), C. chilensis was catalogued as a potential target resource for artisanal fishing in the Juan
Fernández Archipelago. Because of its abundant, large
specimens, the crab became an option for the island
fishers, who are economically dependent on lobster
(Jasus frontalis) extraction. Thus, regular artisanal
fishing of the golden crab began in 2000; annual landings from 2000 to 2006 varied between 2 and 49 tons
a year, with an average of around 17 tons a year
(SERNAPESCA, 2008).
In spite of the development of the fishery, knowledge on the golden crab population off Juan
Fernández is still scarce. The data available was recorded during one exploratory and another experimental fishing trip done in 1996/1997 (Arana, 2000a;
Arana & Vega, 2000). These campaigns revealed a
scant presence of females in the catches and, on average, large-sized specimens. Thus, new biologicalfishing data on C. chilensis is necessary in order to
examine possible changes in its population structure
and to expand understanding of this resource. Therefore, our objective for the present study is to determine the structure of the exploited golden crab stock
around Robinson Crusoe Island in terms of its distribution of size frequencies, sexual proportion, and size
at first sexual maturity.
General aspects
The study was carried out around Robinson Crusoe
Island in the Juan Fernández Archipelago, located
approximately between 33º35´S and 33º50´S and between 78º40´W and 79º50´W. The information was
gathered between July 2005 and May 2006 by sampling the specimens caught during the commercial
fishing operations of artisanal fishers using 9-m-long
wooden boats and rectangular traps (40x70x130 cm)
built with native woods and set between 300 and
1,000 m depth. The operations were carried out in the
fishing areas used by the fishers, which are located to
the north (La Vaquería, Bahía Cumberland), northeast
(Puerto Francés), southeast (Playa Larga), and south
(Bahía Villagra) of the island (Fig. 1).
Structure of the exploited stock
To establish the size structure of the golden crab, the
sampled specimens were separated by sex and then
measured for the carapace length (CL; ± 1.0 mm), or
the straight-line distance over the mid-dorsal axis from
the post-ocular ridge to the posterior limit of the carapace. The size frequency distribution of C. chilensis
was made by grouping the carapace length measurements in 1-mm intervals. In addition, the average size,
variance, and standard deviation were calculated by sex,
month, fishing zone, and the following depths:
350 = 300 to 399 m;
450 = 400 to 499 m;
550 = 500 to 599 m;
650 = 600 to 699 m
750 = 700 to 799 m
850+ = 800 to 1000 m
The global sexual proportion of the samples taken
was established in terms of the percentage of males
present in the catches (% males).
Size-weight relation
A sub-sample was used to establish the size-weight
relationship, measuring the total weight (± 1.0 g) and
the carapace length (± 1.0 mm) of the specimens. We
used the standard power function, in which WLC is the
total whole weight (g) of an individual of CL (mm), a
is the condition, and b the allometry.
WLC = a LC b
The parameters were obtained by minimizing the
sum of the difference of the least squares for the observed and predicted values: E = ∑i =1( Wi − a LCi b )2 .
m
Student's t test was used to establish the type of relative growth (allometric - isometric) presented by the
golden crab (Dixon & Massey, 1957).
First sexual maturity
It tends to be difficult to estimate the size or age at
which male crustaceans mature since they lack external characteristics that can be used for these purposes.
Based on the assumption that, beginning with the
puberty molt, the organisms register a noteworthy
variation in relative growth of some structures
(George & Morgan, 1979; Conan & Comeau, 1986),
the morphometric relationships between the carapace
Size and maturity of the Juan Fernández golden crab
349
Figure 1. Golden crab fishing zones off Robinson Crusoe Island.
Figura 1. Zonas de pesca de cangrejo dorado alrededor de la isla Robinson Crusoe.
length and the chela length (both precise to ± 0.1 mm)
were analyzed. This was done in order to establish the
break in the relationship that could be attributed to the
specimens’ physical maturity (Fernández-Vergaz et
al.,2000). Hence, the methodologies proposed by
Somerton (1980) and Udupa (1986) were taken into
account when determining male maturity, testing the
equality of two linear regressions using the F test (α,
n1-2, n2- 2) ≤ F* (Neter & Wasserman, 1974).
RESULTS
During the development of this research, 13,027 individuals were measured, of which 12,754 were males
and only 273 were females (Table 1). The sexual proportion in golden crabs was characterized by the recurrence of high levels of males throughout the analysis
period, with a global average of 97.9% (Fig. 2).
Between July 2005 and May 2006, females sizes
ranged from CL 68.7 to 150.0 mm, with an average of
94.3 mm, whereas the males had a greater range of
sizes (CL: 46.0 to 189.7 mm) and a significantly
higher average (118.9 mm) (Fig. 3). The average size
of the specimens caught showed a marked difference
between males and females, with males averaging
between 114.4 mm (March) and 130.3 mm (September) and females, lesser in numbers and mean size,
averaging from 91.1 mm (March) to 107.0 mm (September) (Table 1).
The size of the specimens was also analyzed by
fishing zone. The lowest average value (112.2 mm)
was found at La Vaquería, in the north sector of the
island. In the remaining areas, the average carapace
length of the golden crab was higher and similar:
117.1 mm in Bahía Villagra, 118.3 mm in Bahía
Cumberland, and 119.5 mm in Puerto Francés and
Playa Larga (Fig. 4, Table 2). The bathymetry revealed an increasing tendency between average size
and depth; the specimens caught as of 750 m depth
were larger than CL 123 mm, whereas those caught in
the shallower strata averaged from 113.1 to 118.9 mm
(Fig. 5, Table 3).
The size frequency distribution for males was bimodal, with one mode around 100 mm and another,
the most important, around 130 mm. On the other
hand, the females showed a relatively uniform structure with only one modal size at 93 mm (Fig. 6).
In monthly terms, the size range dropped from July
2005 to May 2006 and fewer large specimens were
observed (Fig. 7). Regardless, throughout the analyzed
period, the size structures of the males maintained two
modes. In an analysis of size frequency distribution by
fishing zone, the area corresponding to Bahía Cumberland stands out, having an ample size range and
greater relative importance of specimens over CL 130
mm (Fig. 8). In bathymetric terms, the deeper strata
are lacking smaller specimens; at over 800 m depth,
only specimens over CL 100 mm (Fig. 9) are found.
350
Table 1. Main statistics of the carapace length in golden crabs between July 2005 and May 2006.
Tabla 1. Principales estadígrafos de la longitud cefalotorácica en cangrejo dorado, entre julio 2005 y mayo 2006.
Month
Number of
sampled
specimens
(N)
August
September
October
November
December
January
February
March
April
May
880
1,198
544
669
1,575
562
678
725
2,269
1,819
1,801
12,720
5
23
5
7
16
17
24
4
108
36
24
269
Total
885
1,221
549
676
2
579
702
729
2
2
2
1
Males
46 - 177.4
74.3 - 165
79 -162.1
76.6 - 165.6
69.8 - 148.7
63.1 - 153.7
77.8 - 153.7
80.4 - 153.7
74.1 - 147.1
78,4 - 189.7
75.1 - 170.4
46 - 189.7
86.2 - 114
80.1 - 117.2
97.2 - 111.2
80 - 150
76.1 - 101,1
85.4 - 98
84.1 - 103.6
91 - 100.9
73.2 - 112.9
68.7 - 105.7
87 - 109.4
68.7 - 150
Total
46 - 177.4
74.3 - 165
79 - 162.1
76.6 - 165.6
69.8 - 148.7
63.1 - 153.7
77.8 - 153.7
80.4 -153.7
73.2 - 147.1
68.7 - 189.7
75.1 - 170.4
46 - 189.7
Males
124.6
123.9
129.8
118.2
119.3
119.4
117.7
119.3
114.0
117.1
114.3
118.5
Females
95.2
104.9
106.6
98.0
90.7
92.2
94.5
96.3
90.6
94.4
95.3
93.9
Total
124.5
123.6
129.6
118.0
119.0
118.6
116.9
119.1
112.9
116.6
114.1
118.0
Males
130.0
127.3
132.8
121.3
121.7
122.6
120.7
122.2
116.4
119.4
115.1
120.6
Females
92.0
110.6
107.0
91.5
90.8
93.0
95.2
96.6
91.2
93.2
95.6
93.2
Total
129.5
126.3
132.6
121.0
121.5
122.2
120.2
122.1
115.2
119.1
114.9
120.1
Males
20.0
19.2
17.4
17.1
15.2
13.5
15.0
13.8
14.4
13.5
14.1
16.1
Females
11.0
12.6
5.7
24.1
6.2
3.3
5.7
4.1
6.9
7.4
5.9
9.0
Total
20.1
19.3
17.5
17.3
15.4
14.1
15.3
13.9
15.0
13.7
14.2
16.3
Males
Females
Range (mm) Females
Mean
(mm)
Median
(mm)
Standard
deviation
(mm)
Total
July
351
Figure 2. Global sexual proportion (% males) of golden crabs recorded between July 2005 and May 2006.
Figura 2. Proporción sexual global (% machos) en cangrejo dorado, registrado entre julio 2005 y mayo 2006.
Figure 3. Average, standard deviation, and maximum
and minimum carapace length of the golden crabs by sex.
Figura 3. Promedio, desviación estándar y valores
máximos y mínimos de la longitud cefalotorácica en
cangrejo dorado, por sexo.
and minimum carapace length of male golden crabs by
fishing zone.
machos de cangrejo dorado, por zona de pesca.
and minimum carapace length of male golden crabs by
depth.
machos de cangrejo dorado, por estrato de profundidad.
352
Table 2. Main statistics of the carapace length in male golden crabs by fishing zone.
Tabla 2. Principales estadígrafos de la longitud cefalotorácica en machos de cangrejo dorado, por zona de pesca.
Number of
specimens
2 196
Mean
(mm)
118.3
Standard deviation
(mm)
7.2
Puerto Francés
5 929
119.5
3.9
Playa Larga
1 104
119.5
5.1
695
117.1
6.7
1 515
112.2
5.5
Fishing zone
Bahía Cumberland
Bahia Villagra
La Vaquería
Due to the limited catches of females, the sizeweight relationship was defined by analyzing a sample
of 264 males. The estimated growth factor (b) was
3.0694, whereas the condition factor (a) was 0.0004.
According to the isometry test, this shows an isometric
growth factor (Table 4).
The sexual maturity of the males was determined
using the carapace length (CL) and chela length (QL)
from a sample of 1,067 specimens whose sizes varied
between CL 71 and 141 mm. Before establishing the
CL QL-1 relationship, the values were grouped by
determining the average QL in each range of CL 1
mm. These values, when graphed, revealed a break in
the relationship between these two variables at CL 100
mm, establishing the following statistically different
linear functions (Fig. 10), which show that physical
maturity occurs at CL 100 mm in males:
QL1 = 0.85697 CL − 7.47098
in the range between CL 71 and 100 mm; and
QL2 = 0.99243 CL − 17.85592
in the range between CL 100 and 141 mm
Given the two important modes found for male
golden crabs, a bimodal distribution made up of mature and immature individuals was determined for the
captured specimens. Thus, the maturing process occurs within the size range of the first modal group and,
supposing a normal distribution within this, its ave age
would be the established physical maturity size (CL:
100 mm). Using numerical approximation, it was
possible to establish the fraction of mature specimens
in each size range. Finally, through a non-linear fit of
the data to the sigmoid curve, the curve’s parameters
were set, thereby determining the first sexual maturity
in male golden crab (SSM50%) at CL 109 mm (CW:
125 mm) (Fig. 11).
Figure 6. Distribution of size frequencies in golden crabs
by sex.
Figura 6. Distribución de frecuencias de tallas en cangrejo dorado, por sexo.
353
2006
2005
6
6
Jul/05
n = 880
5
5
4
4
3
3
2
2
1
1
0
0
6
6
Aug/05
n = 1,198
5
Feb/06
n = 725
5
4
4
3
3
2
2
1
1
0
0
6
Relative frequency (%)
Jan/06
n = 678
n = 544
Sep/05
6
5
5
4
4
3
3
2
2
1
1
0
0
6
n = 669
Oct/05
n = 2,269
6
5
5
4
4
3
3
2
2
1
1
0
0
Mar/06
n = 1,819
Apr/06
6
6
May/06
n = 1,801
Nov/05
n = 1,575
5
5
4
4
3
3
2
2
1
1
0
0
50
65
80
95
110
125
140
155
170
Carapace length (mm)
6
n = 562
Dec/05
5
4
3
2
1
0
50
65
80
95
110
125
140
155
170
Figure 7. Monthly distribution of size frequencies in male golden crabs from July 2005 to May 2006.
Figura 7. Distribución mensual de frecuencias de tallas en machos de cangrejo dorado, julio 2005 a mayo 2006.
354
6
10
Bahía Cumberland
5
N = 234
300 m
N = 2,196
8
4
6
3
4
2
2
1
0
0
10
400 m
6
N = 395
8
Puerto Francés
5
N = 5,929
6
4
4
3
2
2
0
1
10
500 m
0
N = 268
6
6
Playa Larga
N = 1,104
5
8
4
3
2
1
0
4
2
0
10
600 m
N = 123
8
6
4
6
Bahía Villagra
N = 695
5
2
0
4
3
10
2
8
1
6
0
4
N = 57
700 m
2
6
La Vaquería
N = 1,515
5
0
4
10
3
8
2
6
1
4
≥ 800 m
N = 67
2
0
45
65
85
105
125
145
165
0
50
60
70
80
90
100 110 120 130 140 150 160
Figure 8. Distribution of size frequencies in male golden
crabs by fishing zone.
Figura 8. Distribución de frecuencias de talla en machos
de cangrejo dorado, por zona de pesca.
Figure 9. Distribution of size frequencies in male golden
crabs by depth.
Figura 9. Distribución de frecuencias de talla en cangrejos dorados machos, por estrato de profundidad.
355
Figure 10. Relationship between carapace length and chela length in male golden crabs.
Figura 10. Relación entre la longitud cefalotorácica y la longitud de la quela en machos de cangrejo dorado.
Figure 11. Ojive of maturity determined for male golden crabs.
Figura 11. Ojiva de madurez determinada en machos de cangrejo dorado.
Table 3. Main statistics of the carapace length in male golden crabs by depth.
Tabla 3. Principales estadígrafos de la longitud cefalotorácica en machos de cangrejo dorado, por estrato de profundidad.
Depth (m)
Number of
specimens
Mean length
(mm)
Standard deviation
(mm)
350 (300 - 399)
234
118.9
9.2
450 (400 - 499)
395
113.1
7.0
550 (500 - 599)
268
113.7
9.5
650 (600 - 699)
123
118.0
22.6
750 (700 - 799)
57
123.3
18.0
850+ (≥ 800)
67
124.7
7.2
356
Table 4. Regression parameters by region and sex of the
carapace length-total weight relationship in golden crab.
Tabla 4. Parámetros de regresión, por región y sexo, de
la relación longitud-peso de cangrejo dorado.
Males
Estimate
Standard error
t-Student
p value
Bottom limit
Top limit
a
b
0.0004
0.000067
6.394724
0.000000
0.000297
0.000560
3.069
0.032472
94.52792
0.000000
3.005613
.133300
Correlation coefficient (R)
Sample (n)
0.9958
264
DISCUSSION
One characteristic of the golden crab fishery is the fact
that it is carried out almost exclusively on male
specimens. In fact, the percentage of males caught was
97.9%, similar to the value determined by Arana
(2000a) prior to the development of commercial fishing; this author estimated a value of 98.1%, whereas
Arana (2000b) and Arana & Vega (2000) estimated a
value of 97.8%. Low proportions of females were also
found by McElman & Elner (1982) for Geryon quinquedens over the Scottish platform; by Wenner et al.
(1987) for Geryon fenneri off the coasts of South
Carolina and Georgia; and by Kendall (1990) for the
golden crab fishery of Georgia. Likewise, Pinho et al.
(2001) determined a male predominance of 1.7:1
(63%) for Chaceon affinis off the Azore Islands,
whereas López-Abellán et al. (2002) determined a
male proportion of 57% (1:0.74) for this same species
off the Canary Islands.
According to Barea & Defeo (1986), this could be
explained i) by the trap soak time, which would allow
smaller specimens to escape (and females are, in general, smaller), and ii) by the low mobility of the females, which would not enter the traps. Another explanation could be a stratification of the sexes by
depth or a different spatial distribution; however, such
a situation has not yet been found in these islands.
The results for the size of the specimens caught in
this investigation differ from those obtained in the
exploratory and experimental fishing campaigns carried out in 1996-1997. First, the size range in the present study is wider, including specimens from CL 46
to 189.7 mm. These sizes exceed the results of Arana
(2000a), who recorded specimens between CL 86 and
140 mm, and those of Arana & Vega (2000), who
reported individuals from 84 to 147-mm.
In spite of the larger size rage found herein, the average size of the males (118.9 mm) was lower than in
1997 (123.0 mm). This is due to the increased representation of smaller specimens, evident when observing the size frequency distributions of the two relevant
modal groups (CL: 130 and 100 mm). It should be
noted that the first mode was not apparent in the size
structures found by Arana (2000b) during the experimental fishing done in 1996-1997.
The differences detected in both the size structure
and the average size of the specimens caught is mainly
due to the fact that the previous results correspond to
the development of experimental fishing operations
intended to evaluate catches using different kinds of
traps and diverse depth ranges. Such variables are
absent in commercial fishing, as the fishers have
adopted one kind of fishing gear and determined the
best places to fish for golden crab.
Nonetheless, the difference in the size frequency
distributions between both sexes coincides with reports by other authors for C. affinis (Pinho et al.,
2001; López-Abellán et al., 2002) and shows a general
pattern for geryonids. Similarly, Melville-Smith
(1989) attributes this difference in C. maritae to the
different molting process of males and females, stating
that the unimodal structure of the latter could be the
result of short intermolt periods in immature specimens and long periods after maturity.
In general, sexual maturity studies have been based
on functional characteristics that show mating capacity (Goshima et al., 2000; Gardner & Williams, 2002),
physiological characteristics (the presence of spermatophores) (Warner, 1977; Melville-Smith, 1987;
Comeau & Conan, 1992), and/or morphometric features such as the use of some physical trait to distinguish between mature and immature individuals
(Somerton, 1980; Conan & Comeau, 1986; Comeau &
Conan, 1992; Gardner & Williams, 2002). In this last
case, the morphometric (or physical) maturity of the
males has been determined by analyzing the relationships between body size and the dimension of some
body parts (Hall et al., 2006).
Due to the scarce female specimens caught for this
study, it was not possible to establish the sexual maturity (SSM) of the female golden crabs. However,
since females are smaller than males and the smallest
female caught with eggs under the abdomen measured
CL 81 mm, we can estimate an SSM for females to be
around this carapace length (CW 95 mm, according to
the CL/CW relationship determined by Arana, 2000b).
357
Table 5. Estimates of size at sexual maturity for the genus Chaceon carried out by diverse authors. CW: carapace with, LC: carapace lengh.
Tabla 5. Estimaciones de talla de madurez sexual en el género Chaceon efectuadas por diversos autores. CW: ancho cefalotorácico, LC: longitud cefalotorácica.
Size at sexual maturity
(mm)
Males
Females
Author
Type of
measurement
Species
Location
Methodology
Chaceon affinis
Canary Islands
Morphometric relations
Gonad maturity
129
-
99.3
109
CW
CW
Fernández-Vergaz et al. (2000)
Chaceon affinis
Azore Islands
Macroscopic observation
-
83
CL
Pinho et al. (2001)
Chaceon quinquedens
Chesapeake Bay
Gonad maturity
-
80-91
CW
Haefner (1977)
Chaceon quinquedens
Canada
Gonad maturity
>115
-
CW
Lawton & Duggan (1998)
Chaceon maritae
Côte d'Ivoire
Gonad development
105-115
80-90
CW
Le Loueuff et al. (1978)
Chaceon maritae
Senegal
100
83
CW
Gaetner & Laloé (1986)
Chaceon maritae
Namibia
Histological analysis
>80
100
CW
Melville-Smith (1987)
Chaceon notialis
Brasil
Vulva condition and eggs
69
97
84
CW
Sant’Ana & Pezzuto (2009)
Chaceon notialis
Uruguay
Gonad maturity
-
70.2-71.7
CW
Delgado & Defeo (2004)
Chaceon chilensis
Juan Fernández
Archipelago
109
-
CW
Present study
358
In males, a change occurred in the relationship between carapace and chela length at CL 100 mm (that
is, CW 115 mm). According to the growth estimate
done for this resource, the size of the first physical (or
morphometric) maturity corresponds to the change in
the molting state, possibly between the modal classes
of CL 100 and 109 mm. It should be noted that this
length is comparable to estimates made by diverse
authors for other Chaceon species (Table 5).
The methodological focus used was based on the
affirmation of Hartnoll (1974), who indicated that
some species might present ontogenic variations in the
relative growth pattern of some body parts that can be
translated into differences in the development between
sexes and/or between immature and mature specimens. In morphometric relationships, these changes
contribute to the reproductive behavior and are required for successful reproduction. In some brachyurans, the size of the chela in males is particularly important in the reproductive process, whether for fighting over females, courting, copulating, or protecting
the females after mating.
It is important to note that males can be functionally and physiologically mature before being able to
reproduce, and that the reproduction capacity is
achieved upon reaching morphometric or physical
maturity (Hall et al., 2006). From this point of view,
the size at first sexual maturity (SSM50%) as such
would occur at sizes greater than those of morphometric or physical maturity, as determined herein.
Our results ratify that the golden crab fishery is
sustained mainly by males, an important aspect for
future fishery management and one that will require
constant monitoring since a reduction in the number of
males could influence the sustainability of the stock.
Thus, it is also important to determine the size at
which males reach sexual maturity (Conan & Comeau,
1986; Ennis et al., 1988; Wenner, 1990; Gardner &
Williams, 2002), as this is an important reference
parameter for management. The results obtained in
this study are favorable since the average size of the
males caught (CL: 118.9 mm) exceeded the SSM50%
(CL: 109 mm).
Finally, we would like to point out that, in the particular case of the Juan Fernández golden crab fishery,
the fishers themselves have established a minimum
saleable size of CW 130 mm (Arana et al., 2006),
equivalent to CL 113 mm. This value is also higher
than the SSM50%, and so we can conclude that the C.
chilensis stock is, at least from this point of view,
protected from overexploitation by recruitment, although the vulnerability presented due to the mainly
male catches must also be taken into account.
ACKNOWLEDGEMENTS
The authors thank the Sindicato de Pescadores Artesanales del Archipélago de Juan Fernández, particularly those who collaborated with sampling off Robinson Crusoe Island and the fishermen Pedro Chamorro,
Mario Llanquín, and Danilo Rodríguez, who allowed
sampling of catches in their boats. This article was
generated with results from two projects: “Monitoreo
biológico-pesquero de la langosta y el cangrejo dorado
en el archipiélago de Juan Fernández” (FIP Project
2004-48) and “Evaluación del stock y distribución de
cangrejo dorado y langosta en el archipiélago de Juan
Fernández” (FIP Project 2005-21), financed by the
Fondo de Investigación Pesquera (FIP) and carried out
by the Pontificia Universidad Católica de Valparaíso.
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Lat. Am. J. Aquat. Res., 37(3): 361-370, 2009Fishing yields and size structures of Patagonian toothfish
361
Research Article
Fishing yields and size structures of Patagonian toothfish (Dissostichus
eleginoides) caught with pots and long-lines off far southern Chile
1
ABSTRACT. Herein, we compare information taken from the Patagonian toothfish (Dissostichus eleginoides)
fishery operations carried out off the far southern coast of Chile (47°00’S-57°00’S) using pots (pots) and longlines. In January 2006 and from June to October 2006, 167 fishing hauls were done, 119 using long-lines and
48 using pots. The total Patagonian toothfish catch was 60.9 tons, of which 81.2% were caught with long-lines
and 18.8% with pots. On average, 5,395 hooks and 147 pots were set per haul, with average yields of 0.08 kg
hook-1 and 1.43 kg pot-1. The average depth for setting the gear was 1,581 m (long-lines) and 1,318 m (pots).
Significant differences were found between these two types of gear, as well as between the time of setting and
the time of retrieval. Greater fishing yields were obtained from the long-line fishery operations, with
significant differences between the gear types in terms of the catch per haul (kg haul-1) and the catch per length
of the specimens retained (kg 1000 m-1). On average, the individuals caught with pots (110.8 cm total length)
were larger than those caught with long-lines (105.1 cm total length). Nonetheless, no significant differences
were recorded for the size structures. In terms of interactions with birds, during setting, no birds were observed
at the trapping operations, whereas a few specimens (≤ 10 birds) were seen during only 2.5% of the long-line
operations. During retrieval, birds were observed during 34.9% of the hauls with pots and 62.8% of the longline operations. The presence of mammals around the fishery operations during setting and retrieval was
similar for both types of gear.
Keywords: yields, pot, long-line, Patagonian toothfish, Dissostichus eleginoides, Chile.
Rendimientos de pesca y estructuras de tallas de bacalao de profundidad (Dissostichus
eleginoides) capturados con trampas y espineles en el extremo sur de Chile
RESUMEN. Se compara información proveniente de operaciones de pesca de bacalao de profundidad (Dissostichus eleginoides) efectuadas mediante trampas y espineles en enero de 2006 y entre junio y octubre de
2006, frente a la costa sur-austral de Chile (47°00’S-57°00’S). Se realizaron 167 lances de pesca, 119 correspondieron a operaciones de pesca con espinel y 48 con trampas, registrándose una captura total de bacalao de
profundidad de 60,9 ton, de las cuales 81,2% fue extraída con espinel y 18,8% con trampas. Se calaron en
promedio 5.395 anzuelos/lance y 147 trampas/lance, obteniéndose un rendimiento promedio de 0,08 kg anzuelo-1 y 1,43 kg trampa-1. La profundidad media de calado fue 1.581 m con espineles y 1.318 m con trampas, encontrándose diferencias significativas entre ambos aparejos, al igual que en el tiempo de calado y de virado.
En las operaciones de pesca con espinel se obtuvo rendimientos de pesca superiores, siendo estas diferencias
significativas entre los aparejos en términos de la captura por lance (kg lance-1) y la captura por longitud de retenida (kg 1000 m-1). Respecto del tamaño de los ejemplares capturados, aquellos pescados con trampas exhibieron talla promedio superior a los extraídos con espineles, registrándose valores medios de 110,8 y 105,1
cm de longitud total, respectivamente; sin embargo, la estructura de talla no registró diferencias significativas.
En relación a la interacción con aves, durante el calado con trampas no se observó presencia de ellas, mientras
que con espineles sólo en el 2,5% de los lances se detectaron algunos ejemplares (≤ 10 aves). En la etapa de
virado, las aves se observaron en el 34,9% de los lances con trampas y en el 62,8% en las faenas con espineles.
362
La presencia de mamíferos en las operaciones de pesca con ambos aparejos tanto en el calado como el virado
fue similar.
Palabras clave: rendimientos, trampa, espinel, bacalao de profundidad, Dissostichus eleginoides, Chile.
________________________
INTRODUCTION
The Patagonian toothfish (Dissostichus eleginoides
Smitt, 1898) is a demersal species found widely in the
southern realms of the Atlantic, Pacific, and Indian
oceans, especially between 40º and 60º S. This species
is found all along the continental coast of South America, from northern Peru to far southern Chile. Its
bathymetry covers 70 to 2,800 m and, in Chilean waters, specimens have been caught at up to 2,500 m
depth (Young et al., 1998). Most Patagonian toothfish
fisheries are between 1,000 and 1,500 m (Young et al.,
1996).
Given its wide Antarctic circumpolar distribution,
D. eleginoides is caught mainly around the southern
cone of America, the Falkland/Malvinas islands,
South Georgia Island, and numerous other islands and
oceanic elevations (Gon & Heemstra, 1990). A large
part of the distribution of this resource is located in the
Sub Antarctic and the Antarctic and its exploitation
therein is regulated by the standards adopted by the
Convention for the Conservation of Live Antarctic
Marine Resources (CCRVMA).
In Chile, Patagonian toothfish fisheries began in
1955, but it was not until the 1970s that an artisanal
fleet in the central sector of the country began commercial exploitation of the species. Later, this same
group expanded operations northward and then
southward, where fishing yields improved (Oyarzún et
al., 2003a, 2003b). At present, the fishery is divided
into two zones. The north zone, between Chile’s
northern limit (18º21’S) and parallel 47º’S, is reserved
exclusively for artisanal fishing whereas, in the south
zone (47ºS to 57º’S), the resource is exploited through
industrial fishing activities.
Technologically, given the resource’s bathymetric
distribution, any fishing gear used to catch Patagonian
toothfish must meet strength standards that allow hauling aboard heavy, large-sized specimens, generally
from depths over 1,000 m. At the end of the 1960s,
Pavez et al. (1968) designed a special long-line to be
used at such depths. This long-line was adopted by the
artisanal fishers that first exploited this resource. Later
attempts to use gills nets and large, heavy rectangular
traps were not very effective and, thus, the long-line
was determined to be the most efficient fishing technique (Zuleta et al., 1996).
The worldwide Patagonian toothfish fishery relies
largely on bottom-set long-lines. In Chile, the rapid
expansion of the fishery as of the 1990s resulted in the
introduction of new fishing techniques, consolidating
the design of a new fishing gear, the Spanish longline, also known as “quebrado” or “retenida”. This
new design was successful in allowing fishing under
any sea conditions and at greater depths (Cascorbi,
2004). In Chilean waters, the gear used to catch D.
eleginoides is regulated, and the use of any fishing
gear or technique other than the long-line is prohibited.
Nonetheless, the use of long-lines for Patagonian
toothfish fishing operations has also had side effects
such as sea bird mortalities, principally albatross (Diomedea spp.) and petrels (Macronectes giganteus)
(Ashford et al., 1994, 1995, 1996; Barea et al., 1994;
Moreno et al., 2003, among others). Likewise, interactions occur between fishery’s activities and whales,
mostly sperm whales (Physeter macrocephalus) and
orcas (Orcinus orca) (Salas et al., 1987; Ashford et
al., 1996; Moreno et al., 2003). In these cases, the
mammals feed on the specimens caught on the longlines when they are brought on deck, resulting in lost
catches. The interaction is also dangerous for the
whales, who could be harmed or killed when becoming tangled in the gear or when driven off by the fishers (Angliss & DeMaster, 1997).
Thus, the evaluation of other fishing techniques for
catching Patagonian toothfish became pertinent for
both the institutions whose objective it is to safeguard
the ecosystem’s conservation and for the users of the
Patagonian toothfish fishery. One of the options being
considered for the exploitation of this species is the
use of pots or traps. In terms of the principle used for
catching the resource, this method does not differ from
the long-line: both are passive, use bait, and require a
certain resting or soak period to attract the prey. No
experiments have been done to evaluate this fishing
alternative in Chilean waters. However, internationally, a study was done by the United Kingdom in waters off South Georgia Island (Subarea 48.3) in which
pots were used for experimental fishing of Patagonian
Fishing yields and size structures of Patagonian toothfish
toothfish from March to May 2000 (Agnew et al.,
2001).
Therefore, participants in this fishery, with the
consent of the Chilean fishing authority, promoted a
research fishing campaign in order to evaluate the
feasibility and convenience of using pots for the industrial fishing of Patagonian toothfish. The objective
of this study was to compare fishing operations using
this gear with those using long-lines, considering fishing yields as well as the main associated operational
aspects. We also analyzed the respective size structures of the catches obtained with each type of gear
and interactions with birds and mammals.
MATERIALS AND METHODS
This study analyzes information on Patagonian toothfish fishing operations using pots (traps) and longlines along the southern coast of Chile (47°S-57°S)
363
and from 630 to 2,269 m depth. The extractive activities were carried out in two periods: in January and
from June to October 2006. The fishing operations
were performed with the long-line factory vessel
“Tierra del Fuego” (53.6 m long), which is normally
used for commercial fishing of this species. The vessel
was rigged to permit trap deployment without interfering with the equipment or the maneuvers required for
long-line fishing. The main modifications were the
implementation of a telescopic crane (Fig. 1a, 1b), the
construction of a trap retrieval collar (Fig. 1c), and a
rail (Fig. 1d) for moving the traps from the retrieval
platform to the setting position (stern).
A Spanish or “quebrado” type long-line was used.
This gear is used frequently by the industrial fleet for
commercial catches of Patagonian toothfish off far
southern Chile. This gear usually consists of a mother
line (PA ø3.5 mm), leaders (PA ø1.2 mm), and hooks
(No. 9). The traps used were troncoconical in design;
Figure 1. Rigging the vessel to operate with a) pots, b) telescopic crane, c) pot retrieval collar, and d) rail for moving the
pots.
Figura 1. Acondicionamiento de la nave para operar con a) trampas, b) grúa telescópica, c) anillo de recepción de trampas y d) riel para desplazamiento de trampas.
364
with a circular base of 150 cm, an upper part of 86 cm;
they were 90 cm high and made of FE (ø17 mm) and
mesh panels (120 mm for the body and 38 mm for the
mouth). These pots were operated using bait, specifically South American pilchard (Sardinops sagax), the
same species used for long-line fishing.
The pot fishing was done in the fishery grounds
where the fleet typically operates and was randomly
interspersed with long-line fishing. For each haul, the
geographical position, date, depth, setting and retrieval
time, gear soak time, and corresponding catch were
noted, as were the characteristics of the gear used
(mother line length, number of hooks/pots set).
The main test statistics used to compare the pot and
long-line fishing operations were the depth of setting
and the setting, retrieval, and soak times; the corresponding average values were determined. A t-test
(95% confidence interval and n1+n2 -2 g.l.) was used
to compare the operational variables for the two types
of fishing gear.
In terms of fishing yields from long-line and trap
operations, the catch per haul (kg haul-1), catch per
hook set (kg hook-1), and catch per trap set (kg trap-1)
were determined. It should be noted that the comparison of yields for different types of fishing gear is not a
trivial matter, requiring a common unit of effort for
both types of gear. Herein, the soak time (h) for each
gear type and length of the mother line (m) were taken
as the nominal unit of effort. These were used to determine the two indicators – catch per hour the gear
was soaked (kg h-1) and catch per 1,000 m of mother
line (kg 1,000 m-1) – used for the comparative analysis.
To analyze the catches obtained per fishing gear,
Patagonian toothfish specimens were measured at
random according to their arrival on the processing
deck. Each individual was sexed and total length (TL)
was determined with an ichthyometer (± 1 cm). These
records were used to determine the sexual proportion
(% males) of the catches. Furthermore, the respective
size frequency distributions were elucidated and individual measurements of total length were grouped in
2-cm intervals, thereby allowing us to compare the
size structures of the Patagonian toothfish specimens
caught with both types of fishing gear. In each case,
we estimated the mean and median sizes, the variance,
and the standard deviation. For purposes of comparison, in order to establish the differences in the size
structures of the catches, the Kolmogorov-Smirnov
test was used.
Finally, in order to quantify the interaction of the
gear with marine birds and mammals, we recorded the
presence of these animals during setting and retrieval
operations. These interactions were categorized as
either many (> 10), few (≤ 10), or none (0). Later, we
determined the percentage of hauls in which we recorded the presence/absence of these animals with the
different types of fishing gear. Likewise, we noted the
by-catch of birds, indicating the number of birds
caught (live or dead) for each haul.
RESULTS
During the study, 167 fishing hauls were carried out
from 1 to 28 January 2006 and from 17 June to 31
October 2006, spread over the entire study area (Fig.
2). Long-line fishing was done on 119 of the hauls and
trap fishing on the remaining 48. The total catch of
Patagonian toothfish was 60.9 ton, 81.2% from the
long-lines and 18.8% from the pots.
During the two fishing periods, 642,024 hooks
were used, ranging from 2,704 to 10,296 hooks/haul
( x = 5.395 hooks haul-1), and 7,052 pots were used,
ranging from 60 to 238 pots haul-1 ( x =147 pots haul-1).
The average yield obtained by each gear was 0.08 kg
hook-1 and 1.43 kg pot-1.
The fishing hauls were done at average depths of
810 to 2,269 m (long-lines) and 630 to 2,020 m (pots).
The average setting depth differed significantly by
type of gear, averaging 1,581 m for long-lines and
1,318 m for pots (Fig. 3).
The setting of the long-lines required 0.8 h for an
average of 5,395 hooks haul-1, whereas setting the pots
required 0.9 h for 147 pots haul-1. The average retrieval time was 5.2 h (long-lines) and 4.2 h (pots).
Both setting and retrieval times differed significantly.
The average soak time for the long-lines was 17.9 h
and for the pots 19.1 h; this difference was not significant (Fig. 3).
The fishing yields for the long-line operations were
higher than those obtained with traps. The catch per
haul with the traditional gear was 462.1 kg haul-1
whereas, with the pots, it was 253.6 kg haul-1. Likewise, when basing these values on the soak time and
length of the mother line, they were 28.9 ton h-1 and
48.1 kg 1000 m-1 for long-lines and 17.3 kg h-1 and
28.6 kg 1000 m-1 for traps. Although the three indicators revealed clear differences between the types of
gear, these were only statistically significant in terms
of the catch per haul (kg haul-1) and the catch per
length of mother line (kg 1000 m-1) (Fig. 4).
During the study period, we sampled 2,058 specimens from long-lines and 663 from pots (Table 1).
The global sexual proportion of the catches obtained
with the two types of gear varied slightly, with more
365
Figure 2. Locations of the fishing hauls done with long-lines and pots during the study period.
Figura 2. Posicionamiento de los lances de pesca con espinel y trampas efectuadas durante el período de estudio.
Figure 3. Box plot of operational variables recorded with long-lines (e) and pots (t).
Figura 3. Box plot de variables operacionales registradas con espinel (e) y trampas (t).
males caught on long-lines than in pots (65.3% vs
49.6%). Nevertheless, males between 85 and 115 cm
total length predominated the size structures of the
catches from both types of gear (Fig. 5).
On average, the trapped specimens were larger
than those caught on long-lines (110.8 vs 105.1 cm
TL) (Table 1). The size frequency distributions revealed, in both cases, a greater breadth of range in
length for the females. The males showed an important mode of 101 cm TL (Fig. 6). The total size structures of the catches from both types of gear were
similar. In fact, the results of the Kolmogorov-
366
Figure 4. Box plot of yields obtained with long-lines (e) and pots (t).
Figura 4. Box plot de los rendimientos obtenidos con espinel (e) y trampas (t).
Smirnov test confirmed that no significant differences
exist between the size frequency distributions for
long-lines and pots (Fig. 7, Table 1).
Regarding the matter of bird interactions, no birds
were observed during trap setting and only a few (≤ 10
birds) were seen during 2.5% of the long-line settings.
More birds were observed during retrieval, again with
lower numbers for traps than long-lines. Birds were
present, considering both observations of “few” and
“many”, at only 34.9% of the trapping and 62.8% of
the long-line operations (Table 2). During this
study, bird mortality was 0.0031 birds 1000 hooks-1
and only occurred during long-line fishing.
The presence of mammals around trapping and
long-line fishing operations, both during setting and
retrieval, was similar. In fact, with long-lines, mammals were observed in 80.7% of the setting and 99.1%
of the retrieval operations whereas, with the pots,
mammals were observed in 97.8% of the setting and
100% of the retrieval operations (Table 2). The personnel onboard reported that the trapped catch showed
no evidence of attack by mammals.
Figure 5. Sexual proportion of the size at catch of Patagonian toothfish obtained with long-lines and pots.
Figura 5. Proporción sexual a la talla de las capturas de bacalao de profundidad obtenidas con espinel y trampas.
367
Table 1. Main statistics for total length of Patagonian toothfish caught with long-lines and pots and the results of the
comparison of the respective size frequency distributions.
Tabla 1. Principales estadígrafos de la longitud total en bacalao de profundidad capturado con espinel y trampas y resultados de la comparación de las respectivas distribuciones de frecuencias de tallas.
Number of specimens
Range (cm)
Mean size (cm)
Median (cm)
Variance (cm2)
Standard error (cm)
Coefficient of variation
Kolmogorov-Smirnov test
Long-lines
Males
Females
Total
1,331
727
2,058
57 - 171 55 - 183 55 - 183
103.1
108.8
105.1
103.5
110.0
104.8
287.2
619.9
411.7
0.5
0.9
0.5
0.2
0.2
0.2
Dn
Dα=0.05
Males
325
67 - 203
104.9
103.5
321.3
1.0
0.2
0.023
0.26
Pots
Females
338
63 - 221
116.4
113.3
982.1
1.7
0.3
Figure 6. Distribution of size frequencies in Patagonian toothfish by sex and fishing gear.
Figura 6. Distribución de frecuencias de tallas en bacalao de profundidad por sexo y aparejo de pesca.
Total
663
63 - 221
110.8
106.5
690.6
1.0
0.2
368
Figure 7. Distribution of relative and accumulated size frequencies in Patagonian toothfish caught with long-lines and
pots.
Figura 7. Distribución de frecuencias de tallas relativas y acumuladas en bacalao de profundidad capturado con espinel y
trampas.
Table 2. Presence of birds and mammals (%) during gear setting and retrieval operations (long-lines and pots).
Tabla 2. Presencia de aves y mamíferos (%) en las faenas de calado y virado de los aparejos (espinel y trampas).
Percentage of hauls (%)
Setting
Retrieval
N
P
M
N
P
M
None
Few
Many
None
Few
Many
(0 ind.)
(≤ 10 ind.)
(> 10 ind.)
(0 ind.)
(≤ 10 ind.)
(> 10 ind.)
Presence of birds
97.5
2.5
0.0
37.3
51.0
11.8
Presence of mammals
9.3
69.5
21.2
0.9
56.5
42.6
100.0
0,0
0.0
65.1
32.6
2.3
2.2
78.3
19.6
0.0
54.5
45.5
Number of individuals
observed
Presence of birds
Presence of mammals
DISCUSSION
The fishing activity exercised on Patagonian toothfish
has historically been the subject of studies and controversy. The intense exploitation to which the species
has been subjected around the Antarctic continent and
in the waters off southern Chile, as well as the implications of this for the ecosystem, have led to the constant evaluation of long-line fishing operations and
Long-lines
Pots
discussions as to the possibility of using an alternative
fishing gear that would allow efficient fishing without
interfering with other marine populations. However,
such a change requires more experiments to compare
types of fishing gear.
In this sense, the use of traps has been considered
as an alternative to the long-line. However, a comparison of the two presents some difficulties since nominally the effort used for catching the resource with the
two types of gear are not equivalent. Therefore, although hooks and traps use a similar fishing technique, requiring bait to attract the fish and soak time
for the catch process to take place, the traditional yield
indicators used to contrast the results of fishing operations cannot be used herein.
In this case, one of the first aspects of the fishing
operations to compare is whether both types of gear
act on the same fraction of the stock from the point of
view of its structure. According to the size frequency
distributions, although the average specimens caught
with pots were larger than those on the long-lines
(110.8 vs 105.1 cm TL), the size structures revealed
no significant differences. Thus, we can infer that the
differences found are basically associated with factors
related to the operation and effectiveness of the gear.
Our analysis showed significant differences in the
operation of the gear. The long-lines were set at
greater depths; the pots were set at shallower depths
due to problems with the retrieval equipment onboard
that impeded deploying the traps any deeper. Likewise, gear operation differed significantly during setting and retrieval, with the maneuvering time being
longer for long-lines during both operational phases.
The total difference generated in the haul was 1.1 h
(66 min). This value is, in practical terms, irrelevant
and can be attributed to the greater depth at which the
long-lines were set.
The soak time recorded for the two types of gear
differed, but not significantly. Gear soak time is defined a priori and usually does not exceed 24 h in
order to prevent the catch being attacked by “mixines”
or “pulguilla” predators (Anphipoda: Crustacea).
Nonetheless, the soak time is subject to the weather
conditions and, when these are adverse, can last up to
three or more days.
The fishing yields also differed, with greater values
found for the long-lines than for the pots. The catch
per haul with long-lines was nearly double that with
pots (462.1 kg haul-1 vs 253.6 kg haul-1). The same
was true for the yield in function of the length of the
mother line (long-lines: 48.1 kg 1000 m-1 vs pots: 28.6
kg 1000 m-1). In spite of the lack of clarity regarding
the equivalence in the catchability of these two types
of gear – no hook-trap relationship has been defined
and between-gear comparisons are complex – the
results show that the long-lines are more effective.
Hence, from this point of view, the use of pots is not
an option for the near future.
It should be noted that this experience of trapping
Patagonian toothfish is unique in Chile. Only one
similar experiment was found in the literature, a report
by Agnew et al. (2001) of Shag Rocks and the waters
369
to the northeast of South Shetland Island in the South
Atlantic. These authors reported lower yields per pot
than those found herein (1.28 kg trap-1 vs 1.43 kg trap1
). However, they operated under different conditions
and in fishing zones with different abundances.
One of the main advantages of the pots was the
lack of incidents with birds. Nevertheless, birds were
present around the fishing operations. The use of traps
eliminated bird mortality as well as bait consumption
by birds, thereby reducing the real fishing effort by up
to 26% of the line (Brothers & Foster, 1997). It should
be mentioned that, according to the number of hooks
set, the bird mortality rate recorded in the present
study (0.003 birds 1000 hooks-1) was significantly
inferior to that obtained in 2001 by Moreno et al.
(2003), who reported mortality of 0.36 birds 1000
hooks-1.
Interactions with mammals were also altered. The
trapping operation eliminated predatory attacks by
mammals on the catch, with none of the caught
specimens showing signs of having been attacked by
these animals. This is an important factor for the fishery users, since such attacks reduce the effective catch
on the long-line. Moreno et al. (2003) calculated a
monetary loss of US$ 138 per haul caused by marine
mammals and of US$ 92,684 for the entire fleet in the
fishing season, due to the high value of this resource
on the international markets.
The present research shows the feasibility of employing pots for catching Patagonian toothfish. However, this gear was not sufficiently favorable for the
fishers. The main difficulties in using the pots were
operational aspects due, by and large, to the considerable depth at which this resource is caught, the weight
of the gear, and the complexity of its operation. Longlines are clearly more efficient than pots. Here it is
important to mention that, parallel to the execution of
this project, the industrial fleet introduced “cachaloteras” (anti-predation devices) on their long-lines.
This modification basically involves a net that wraps
around the leaders and hooks during retrieval, impeding predation by sperm whales and orcas on the caught
specimens, thereby incrementing the effectiveness of
the long-lines.
The experience of fishing with pots can be repeated successfully with other resources, mainly those
available at lesser depths and that are affected by birds
and/or mammals. Nonetheless, the use of these traps
requires technological changes in the fishing vessels
that should be analyzed and evaluated for the target
species, particularly regarding those aspects related
directly to the capacity of the winches to raise the
gear.
370
Finally, it is necessary to state that adopting the use
of pots as a fishing method necessitates a study of the
impact this change would produce on the exploited
population. Such a study should include the “ghost
fishing” that would arise due to the loss of pots, which
continue to attract and trap specimens indefinitely,
causing mortality that could become significant and
that should be incorporated into the population evaluation models. An evaluation could be done of the use of
biodegradable materials in some sections of the pot
that would allow the organisms to escape after a certain time, thus minimizing or eliminating this additional source of mortality.
ACKNOWLEDGEMENTS
The authors thank Pesca Chile S.A., for allowing us to
carry out the present investigation and, in particular,
the ship-owners of the vessel “Tierra del Fuego” and
all its crew, whose assistance was important during
experimental fishing activities. We especially thank
the Operations Manager, Mr. Enrique Gutiérrez, for
his support and constant collaboration, which helped
make this study a success.
We also thank the Fishery Undersecretary, who
permitted this project, and especially Mr. Marcelo
García for his willingness to resolve administrative
issues for the project.
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and non-serious injury of marine mammals taken incidental to commercial fishing operations: Report of
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Spring, MD, USA, 51 pp.
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Ashford, J.R., J.P. Croxall, P.S. Rubilar & C.A. Moreno.
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Ashford, J.R., P.S. Rubilar & A.R. Martin. 1996. Interactions between cetaceans and longline fishery operations around South Geogia. Mar. Mamm. Sci., 12(3):
452-457.
Received: 24 July 2008; Accepted: 5 August 2009
Barea, L., I. Loinaz, Y. Marin, C. Rios, A. Saralegui, A.
Stagi, R. Vaz-Ferreira & N. Wilson. 1994. Mortality
of albatrosses and other seabird produced by tuna
long-line fisheries in Uruguay. CCAMLR Doc. WGIMALF-94/17.
Brothers, N. & A.B. Foster. 1997. Seabird catch rates: an
assessment of causes and solutions in Australia’s domestic tuna longline fishery. Mar. Ornit., 25: 37-42.
Cascorbi, A. 2004. Seafood watch. Seafood Report:
“Chilean Seabass”. Patagonian toothfish (Dissostichus eleginoides) and Antarctic toothfish (Dissostichus mawsoni). Doc. Monterey Bay Aquarium, 15
pp.
Gon, O. & P.C. Heemstra. 1990. Fishes of the Southern
Ocean. Nototheniidae: Genus Dissostichus. JLB.
Smith Institute of Ichthyology, Grahamstown, South
Africa, pp 285-289.
Moreno, C., R. Hucke-Gaete & J. Arata. 2003. Interacción de la pesquería del bacalao de profundidad con
mamíferos y aves marinas. Informe Final, Proyecto
FIP 2001-31: 211 pp.
Oyarzún, C., S. Gacitúa, M. Araya, L. Cubillos, R. Galleguillos, C. Pino, G. Aedo, M. Salamanca, M. Pedraza & J. Lamilla. 2003a. Asignación de edades y
crecimiento de bacalao de profundidad. Informes
Técnicos FIP-IT/2001-17: 1-74.
Oyarzún, C., S. Gacitúa, M. Araya, L. Cubillos, R. Galleguillos, C. Pino, G. Aedo, M. Salamanca, M. Pedraza & J. Lamilla. 2003b. Monitoreo de la pesquería
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Pavez, P., T. Melo & R. Méndez. 1968. Pesca exploratoria con espineles de profundidad. Informe Técnico
convenio Universidad Católica de ValparaísoMinisterio de Agricultura, Chile, 45 pp.
Salas, R., H. Robotham & G. Lizama. 1987. Investigación del bacalao en la VIII Región. Informe Técnico,
Intendencia Región Bío-Bío e Instituto de Fomento
Pesquero, Talcahuano, 183 pp.
Young, Z., H. Robotham & R. Gili. 1996. Evaluación de
la pesquería y del stock de bacalao de profundidad al
sur del paralelo 47° L.S. Informe Final FIP 94-10: 44
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Young, Z., H. González & P. Gálvez. 1998. Análisis de
la pesquería de bacalao de profundidad en la zona
sur-austral. Informe Final FIP 96-40: 54 pp.
Zuleta, A., C. Moreno, P. Rubilar & J. Guerra. 1996.
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Lat. Am. J. Aquat. Res., 37(3): 371-380, 2009 Haliporoides diomedeae frente a la costa norte de Perú
Research Article
Distribución, abundancia y estructura poblacional del langostino rojo de
profundidad Haliporoides diomedeae (Crustacea: Decapoda: Solenoceridae)
frente a la zona norte de Perú (2007-2008)
Edward Barriga1, Carlos Salazar1, Jacqueline Palacios1, Miguel Romero1 & Aldo Rodríguez1
1
Instituto del Mar del Perú, Esquina Gamarra y General Valle s/n, Chucuito, Callao, Perú
RESUMEN. Se determinó la distribución, abundancia relativa y estructura poblacional de Haliporoides diomedeae frente a la zona norte de Perú (3º30’S-10º00’S), con los resultados de dos cruceros desarrollados en
2007 y 2008 a bordo del B/O Miguel Oliver, que realizó investigaciones de la fauna bentodemersal entre 200 y
1.500 m de profundidad, mediante un muestreo al azar estratificado de arrastre de fondo. En 122 lances realizados en cuatro sectores y tres estratos se capturó un total de 48.056 kg, compuestos por ~347 especies de peces e invertebrados. H. diomedeae fue la especie de langostino más importante en las capturas (411 kg), con
los mayores niveles de abundancia entre 600 y 1.600 m al norte de los 7ºS, con valores medios de captura por
unidad de área (CPUA) entre 83,4 y 211 kg km-2 y una biomasa total estimada de 1.139,74 ton (± 245,6 ton).
Las hembras presentaron una longitud cefalotorácica media de 40,6 mm, rango de 14,5 y 74,5 mm y grupo
modal dominante de 30 mm, mientras que en los machos la media fue de 30,6 mm, rango 16 a 33 mm y grupo
modal principal de 27 mm; para ambos sexos se identificaron seis grupos modales, dimorfismo sexual y gradiente batimétrica. La relación talla-peso fue de tipo alométrico. En general, las características de distribución,
abundancia y estructura poblacional de H. diomedeae permiten considerarla como una especie potencialmente
explotable en el norte del mar peruano.
Palabras clave: Haliporoides diomedeae, distribución, abundancia, estructura poblacional, zona norte, Perú.
Distribution, abundance, and population structure of deep red shrimp
Haliporoides diomedeae (Crustacea: Decapoda: Solenoceridae) off northern
Perú (2007-2008)
ABSTRACT. The distribution, relative abundance, and population structure of Haliporoides diomedeae was
determined off northern Perú (3º30’S-10º00’S) by analyzing data from two cruises carried out in 2007 and
2008 on board the B/O Miguel Oliver to assess the bentho-demersal fauna between 200 and 1,500 m depth, using a stratified random bottom trawl design. The total catch from the 122 hauls (covering four sectors and
three strata) was 48,056 kg, with ~347 fish and invertebrate species. H. diomedeae was the most important
shrimp in the catches (411 kg), with the highest abundance levels between 600 and 1,600 m depth north of
7º00’S. The mean catch per unit area (CPUA) was between 83.4 and 211 kg km-2. The total biomass was estimated to be 1,139.74 ton (± 245.6 ton). The mean carapace length of the females was 40.6 mm, with a range
of 14.5 to 74.5 mm and a main modal group of 30 mm; the mean carapace length of the males was 30.6 mm,
with a range of 16 to 63 mm and a main modal group of 27 mm. Males and females showed six modal groups,
sexual dimorphism, and a bathymetric gradient. The length-weight relationship was allometric. Given the distribution, abundance, and size structure of H. diomedeae off the northern Peruvian coast, it can be considered a
potentially exploitable species in the sea off northern Perú.
Keywords: Haliporoides diomedeae, distribution, abundance, population structure, northern Perú.
________________________
Corresponding author: Edward Barriga ([email protected])
371
372
INTRODUCCIÓN
Desde mediados de la década de los 60’s a la fecha, se
ha desarrollado un importante número de exploraciones pesqueras en las zonas batial y arquibentónica del
mar peruano, a bordo de diferentes buques de investigación (Del Solar & Álamo, 1970; Del Solar & Mistakides, 1971; Vílchez et al., 1971; Del Solar & Flores,
1972; Kameya et al., 1997, 2006b; JDSTA-IMARPE,
2004), para estudiar los componentes faunísticos de
estos hábitat e identificar especies potenciales para el
desarrollo de pesquerías de profundidad. Todas ellas
han señalado a la gamba roja o langostino rojo de
profundidad Haliporoides diomedeae (Faxon, 1893)
como componente importante de su biocenosis, considerándose una especie potencialmente explotable en el
norte de Perú, debido a la amplitud de su distribución
y niveles de abundancia (Del Solar & Álamo, 1970;
Vélez et al., 1992; Kameya et al., 2006a).
Se describen y analizan los resultados de dos campañas de investigación efectuadas en el mar peruano, en
la primavera de 2007 y 2008, a bordo del Buque
Oceanográfico Español B/O Miguel Oliver, cubriendo
la plataforma y talud continental entre 200 y 1.500 m
de profundidad, desde Puerto Pizarro (3º30’S) a
Huarmey (10º00’S) (Fig. 1).
La evaluación se realizó mediante un muestreo al
azar estratificado de fondo, usando una red de fondo
tipo Lofoten con nomenclatura por diseño de 456 x
140 de Polietileno (PE) para fondos duros; con clasificación FAO perteneciente al grupo de redes de arrastre
de fondo con puertas, operada por popa del buque
(OTB-2 Código ISSCFG 03.1.2), con tamaño de malla
en el copo de 35 mm. La duración promedio por operación de pesca (lance) fue de 30 min de arrastre efectivo, monitoreado por el sistema Net sonda ITI
SIMRAD, a una velocidad media de 3 nudos. Todos
los lances fueron realizados durante el día (6:00 a
18:00 h) con un promedio de cinco lances diarios.
El área de estudio fue dividida en cuatro sectores y
cada uno de ellos en tres estratos de profundidad (200500, 500-1000 y 1000-1500 m) (Tabla 1, Fig. 1), totalizando 12 estratos. Cada estrato fue a su vez dividido
en unidades básicas de muestreo (UBM) de 9 mn2 de
área (cuadrantes de 3 x 3 mn), de las que se seleccionó
aleatoriamente una muestra, cuyo tamaño fue proporcional a la extensión del área. Los sectores A y B fueron estudiados durante la campaña 2007 (14 de septiembre al 10 de octubre) y los sectores C y D en la
campaña 2008 (2 de septiembre al 2 de octubre).
Previa a la ejecución de los lances, se realizó el levantamiento batimétrico de las UBM seleccionadas al
azar y con estos insumos se planificó la estrategia de
arrastre. Para la localización de áreas arrastrables se
utilizó un ecosonda Multihaz SIMRAD EM-302 de
rango medio de gran resolución, alta velocidad de
adquisición de datos, fiabilidad y facilidad de operación. Se trabajó con una frecuencia de 30 Khz, con
pulsos de tipo CW y Chirp (Fm), que aseguró una
completa capacidad de “barrido”. En el caso que las
UBM seleccionadas no presentaron condiciones de
arrastre adecuadas, se optó por ubicar una zona adyacente o reasignar aleatoriamente una UBM alterna.
Durante la ejecución de cada lance se registraron
las principales características operacionales (velocidad
de arrastre, tiempo efectivo, posición geográfica, rumbo, longitud del cable, entre otras). Asimismo, se utilizó el sistema Net sonda ITI SIMRAD, con sensores
que registraron la abertura horizontal entre puertas y
alas, abertura vertical, posición de la red, profundidad,
temperatura y registro del cardumen que entra en la
H. diomedeae es un crustáceo decápodo bentónico
de la familia Solenoceridae, que se distribuye desde el
golfo de Panamá (7º30’N) hasta los 42º30’S (Chile)
(Arana et al., 2003), sobre el talud continental a profundidades que varían entre 240 y 1.866 m (Méndez,
1981). En Perú, diferentes estudios han contribuido
significativamente al conocimiento de las características poblacionales y biológicas de esta especie (Del
Solar & Álamo, 1970; Del Solar & Mistakides, 1971;
Vílchez et al., 1971; Del Solar & Flores, 1972; Kameya et al., 1997; JDSTA-IMARPE, 2004). Sin embargo, hasta el momento no se ha desarrollado ninguna
pesquería directa o indirecta de este recurso; manteniéndose las poblaciones de langostinos de profundidad en condiciones prístinas no sometidas a presión de
pesca y potencialmente explotables.
En Chile, la captura de H. diomedeae ha sido considerada como actividad asociada a la pesca de arrastre
dirigida a camarón nailon (Heterocarpus reedi), adquiriendo a partir de 1999 una mayor importancia
relativa dentro de la pesquería de crustáceos demersales, principalmente en la región de Valparaíso (Arana
et al., 2002; SUBPESCA, 2004).
En ese sentido, este documento tiene por objetivo
fortalecer los conocimientos biológicos y poblacionales del langostino de profundidad H. diomedeae, como
recurso potencialmente explotable en el norte del mar
peruano, a partir de los resultados obtenidos en dos
campañas de investigación realizadas en 2007 y 2008,
en el marco del convenio de cooperación suscrito
entre el Instituto del Mar de Perú y la Secretaría General del Mar de España.
Haliporoides diomedeae frente a la costa norte de Perú
boca de la red. La información monitoreada a través
de este equipo permitió controlar los arrastres en sus
diferentes fases y fue insumo para las estimaciones del
área barrida.
El área barrida (Abi) se estableció como el producto de la velocidad (Vi), tiempo efectivo de arrastre (ti)
y abertura horizontal (Ahi) en cada lance:
Abi = ti Vi Ahi
La estimación de la biomasa se realizó mediante el
método de área barrida, que consiste en calcular la
densidad de la especie objetivo, relacionando su captura con el área o sector de barrido efectivo y extrapolándola a la totalidad del área de cada estrato. De este
modo el principal supuesto es que este índice de densidad es proporcional a la abundancia presente en el
área prospectada (estrato) (Alverson & Pereyra, 1969;
Espino & Wosnitza-Mendo, 1984; Sparre & Venema,
1995), considerando un coeficiente de capturabilidad
(factor de eficiencia) equivalente a la unidad.
Como índice de densidad se utilizó la captura por
unidad de área (CPUA expresada en kg km-2), que es
la captura de la especie objetivo en el lance i por unidad de área barrida del mismo lance.
CPUAi =
Ci
Abi
Para el cálculo de la CPUA promedio ( CPUAe ) por
estrato, se consideró la media aritmética de las CPUA
de todos los lances efectuados en el estrato (n).
CPUAe =
∑ CPUAi
n
La biomasa vulnerable (Be) presente en una unidad
espacial (estrato) quedó determinada por el estimador
de la captura por unidad de área ( CPUAe ), amplificado
o expandido al área total (Ae) de la región o conglomerado (estrato), de acuerdo a la siguiente expresión:
Be = CPUAe Ae
y la biomasa total (Bt) corresponde a la sumatoria de
las biomasas estimadas en todos los estratos (Be)
Bt =
e
∑ Be
1
En cada lance, todos los ejemplares de Haliporoides diomedeae fueron separaron por sexo y se les
midió la longitud cefalotorácica (Lc) al mm inferior,
con un calibre (vernier) de 0,1 mm de precisión, y su
correspondiente peso corporal (g) con una balanza
digital (0,01 g de precisión). Con estos datos se analizó la proporción sexual, estimada como el número de
373
hembras o machos en relación al número total de
ejemplares muestreados por rango de talla; se obtuvo
la estructura de tallas por distribución de frecuencias
agrupadas en rangos de 1 mm de Lc (por sexo, sector
y estrato) y en grupos modales que fueron determinados por el método de Bhattacharya siguiendo la rutina
específica en el programa FiSAT II (Gayanilo & Pauly, 1997; Gayanilo et al., 2003). Se estimó la talla
media y desviación estándar para cada caso; asimismo, se analizó la relación talla-peso a través de la
función de poder tradicional, cuyos parámetros se
estimaron con ajuste de mínimos cuadrados, linealizando la función mediante el logaritmo natural (ln)
(Sparre & Venema, 1995).
Toda la información, producto de los muestreos,
fue inicialmente recopilada en formularios y posteriormente almacenada y procesada en hojas de cálculo
Excel.
RESULTADOS
Durante las campañas de 2007 y 2008 se ejecutaron
122 operaciones de pesca (lances) que cubrieron todos
los sectores y estratos del área de estudio (Tabla 1,
Fig. 1). Se obtuvo 48.055,57 kg de captura total, de los
cuales el 92% correspondió a 147 especies de peces,
4,2% a 68 especies de crustáceos, 1,3% a 34 especies
de equinodermos, 1,1% a 35 especies de moluscos y el
resto a 33 especies de otros grupos taxonómicos, como
poliquetos y cnidarios.
De todas las especies de langostinos capturados, la
gamba roja Haliporoides diomedeae fue la más importante en las capturas (411 kg), con alta presencia en
los lances efectuados a profundidades mayores de 500
m (Tabla 2), principalmente en los sectores A y B
(norte de 7ºS), seguido en importancia por Benthesicymus tanneri, Heterocarpus vicarius, H. hostilis y
Nematocarcinus agassizii.
H. diomedeae se distribuyó entre 600 y 1600 m, estando ausente en profundidades menores a 500 m. Se
distinguieron tres zonas con diferencias en distribución y abundancia: la primera, al norte de los 4º30’S
con mayor abundancia entre 600 y 1000 m; la segunda, entre 4º30’S y 7º00’S con amplia presencia y con
los mayores valores de abundancia entre 1000 y 1500
m de profundidad, y la tercera zona ubicada al sur de
los 7ºS, con bajos niveles de abundancia relativa, entre
600 y 1200 m (Figs. 1 y 2).
La mayor abundancia relativa de H. diomedeae se
encontró en los estratos 2 y 3 de los sectores A y B,
con valores medios entre 191,7 kg km-2 y 211 kg km-2,
374
Tabla 1. Número de operaciones de pesca (lances) efectuados durante dos campañas de investigación (2007-2008), por
sectores y estratos de profundidad.
Table 1. Number of fishing operations (hauls) carried out during two research cruises (2007-2008), by sector and stratum.
Sector
Estrato (m)
A
B
C
D
3º30’S-5º00’S
5º00’S-7º00’S
7º00’S-8º30’S
8º30’S-10º00’S
Total
1
200-500
13
7
18
10
48
2
500-1000
9
9
12
10
40
3
1000-1500
7
11
8
8
34
29
27
38
28
122
Total
Figura 1. a) Distribución geográfica de las operaciones de pesca de arrastre por estrato y sector. b) Distribución y abundancia relativa (kg km-2) de Haliporoides diomedeae frente a la zona norte de Perú. Cruceros de investigación 2007 y
2008.
Figure 1. a) Geographic distribution of trawl fishing operations (hauls) by strata and sector. b) Distribution and relative
abundance (kg km-2) of Haliporoides diomedeae off northern Perú. Research cruises in 2007 and 2008.
375
Tabla 2. Porcentaje de lances con presencia de Haliporoides diomedeae por sector y estrato, en dos cruceros de investigación frente a la zona norte de Perú (2007-2008).
Table 2. Percentage of fishing operations (hauls) with catches of Haliporoides diomedeae during two research cruises off
northern Perú (2007-2008) by sector and stratum.
Estrato (m)
1
2
3
Total
200-500
500-1000
1000-1500
A
3º30’S-5º00’S
15.38
100,00
100,00
62,07
Sector
B
C
5º00’S-7º00’S 7º00’S-8º30’S
77,78
100,00
66,67
D
8º30’S-10º00’S
75,00
87,50
42,11
Total
4,17
80,00
82,35
50,82
70,00
37,50
35,71
Figura 2. Variación latitudinal y batimétrica de la distribución y abundancia relativa (log CPUA+1) de Haliporoides
diomedeae frente a la zona norte de Perú (el tamaño de las burbujas es proporcional a los valores de abundancia relativa).
Cruceros de investigación 2007 y 2008.
Figure 2. Latitudinal and bathymetric variations of distribution and relative abundance (log CPUA+1) of Haliporoides
diomedeae off northern Perú (bubble size is proportional to relative abundance). Research cruises in 2007 and 2008.
respectivamente, mientras que en los sectores C y D la
mayor abundancia se obtuvo en el estrato 2 con valores de 26,34 kg km-2 y 13,83 kg km-2 respectivamente
(Tabla 3). La biomasa total estimada por el método de
área barrida fue de 1.139,74 ton (± 245,6 ton), de las
cuales el 89% se registró en los estratos 2 y 3, entre
3º30’S y 7º00’S (Tabla 4).
Para determinar la estructura por tallas de H. diomedeae en el área evaluada, se midió la longitud cefalotorácica de 5.701 individuos, de los cuales el 64,4%
fueron hembras y 35,6% machos. Las hembras presentaron una talla media de 40,6 mm en un rango de 14,5
y 74,5 mm con al menos seis grupos modales distinguibles (17, 30, 40, 48, 57 y 60 mm), de los cuales el
Tabla 3. Captura por unidad de área (kg km-2) de Haliporoides diomedeae por sector y estrato.
Table 3. Catch per unit of area (kg km-2) of Haliporoides diomedeae by sector and stratum.
Sector
B
A
Estrato
CPUA (kg km-2)
Desv. estándar
CPUA (ton mn-2)
Biomasa (ton)
1
0,05
0,15
0,0002
0,11
2
191,70
94,36
0,658
271,84
3
210,97
204,58
0,724
232,58
1
2
83,44
137,42
0,286
132,38
C
3
196,89
100,72
0,675
373,33
1
2
26,34
41,24
0,090
71,79
D
3
14,47
19,50
0,050
24,96
1
2
13,83
19,43
0,047
29,42
3
1,62
2,73
0,006
3,35
376
Tabla 4. Biomasa (ton) estimada de Haliporoides diomedeae por sector. IC: intervalo de confianza, CV: coeficiente de variación.
Table 4. Biomass (ton) of Haliporoides diomedeae by
sector. IC: confidence interval, CV: coefficient of variation.
Sector
Total
A
B
C
D
Biomasa (ton)
504,52
505,70
96,74
32,77
1139,74
IC (± ton)
169,08
164,91
62,93
23,96
245,59
17,10
16,64
33,19
37,30
10,99
CV %
grupo de 30 mm fue el más abundante en el estrato 2
de todos los sectores, representando el 44% del total.
Los machos se presentaron en un rango de tallas entre
16 y 63 mm de longitud cefalotorácica, talla media de
30,6 mm y seis grupos modales (17, 27, 34, 38, 43 y
50 mm) de los cuales el grupo de 27 mm fue el más
abundante en las capturas (60%), principalmente en el
estrato 2 de toda el área, mientras que el grupo de 34
mm lo fue en el estrato 3. La diversidad de grupos
modales fue similar en todos los sectores (Fig. 3).
Hembras y machos mostraron un gradiente batimétrico de tallas, los ejemplares más grandes se encontraron a mayor profundidad. No es claramente distinguible una gradiente latitudinal. La discriminación por
grupos modales mostró un notable dimorfismo sexual,
que se hizo más evidente a partir del grupo 2 (~28
mm). Las hembras y los machos del grupo 3 presentaron talla media de ~40 y ~34 mm respectivamente; el
grupo 4 en hembras tuvo ~48 mm y en machos ~38
mm; y el grupo 5 tuvo una talla media de ~57 mm
para hembras y ~43 mm en machos (Tabla 5).
El análisis de la proporción sexual por tallas, permitió distinguir que en los grupos más juveniles hubo
un predominio de machos en una proporción de 3:1
(tres machos por una hembra), situación que se revirtió a partir de 36 mm, donde las hembras fueron dominantes, alcanzando casi la totalidad en tallas superiores a 45 mm (Fig. 4). La alternancia observada en
30 y 34 mm fue basada en el dimorfismo sexual, es
decir no hubo un grupo importante de machos formando un grupo modal en 30 mm (grupo 2, en el que
los machos miden 27 mm), asimismo no hubo un grupo de hembras formando un grupo modal en 35 mm
(grupo 3, donde las hembras tienen 40 mm).
Figura 3. Frecuencia relativa (%) de la longitud cefalotorácica (mm) de Haliporoides diomedeae por sectores (A, B, C y
D), en los estratos 2 y 3, en hembras y machos.
Figure 3. Relative frequency (%) of carapace length (mm) of Haliporoides diomedeae by sectors (A, B, C, D) and strata 2
and 3, for females and males.
377
Las relaciones talla (longitud cefalotorácica) y peso corporal (g) mostraron una relación del tipo alométrico negativo (Fig. 5), similar a lo reportado por Arana et al. (2003).
Tabla 5. Longitud cefalotorácica (Lc mm) media y porcentaje de incidencia de los grupos modales por sexo de
Haliporoides diomedeae. DE: desviación estándar.
Table 5. Mean carapace length (Lc mm) and incidence
(%) of modal groups by sex for Haliporoides diomedeae.
DE: Standard deviation.
Grupo
1
2
3
4
5
6
Hembras
Lc Media DE
%
17,2 1,6
1,13
29,6 2,7 42,78
40,0 1,9 20,15
47,8 3,1 23,54
56,8 2,4
7,37
61,7 2,2
5,03
Machos
Lc Media DE
17,3 1,0
27,4 2,1
34,0 1,4
38,1 1,7
42,8 1,8
49,5 0,4
%
0,62
59,53
21,82
13,55
4,27
0,21
Figura 4. Proporción sexual de hembras y machos por
rango de talla de Haliporoides diomedeae.
Figure 4. Sexual proportion of females and males of
Haliporoides diomedeae by size range.
Figura 5. Representación de la relación talla-peso de Haliporoides diomedeae por sexo y ajuste de la curva de poder
correspondiente, frente a la zona norte de Perú (2007-2008). a) Hembras, b) machos, y c) total.
Figure 5. Length-weight relationship representation of Haliporoides diomedeae by sex and power curve adjust, off
northern Perú (2007-2008). a) Females, b) males, and c) total.
378
DISCUSIÓN
La amplia presencia del langostino de profundidad
Haliporoides diomedeae en el área estudiada, confirma la existencia de condiciones ambientales favorables para el desarrollo biológico y poblacional de esta
especie, principalmente en el rango de 600 a 1500 m
entre 4º30’S y 7º00’S, relacionado con la presencia del
Agua Intermedia Antártica (Kameya et al., 1997),
fondo fangoso-arenoso (Méndez, 1981) y fuertemente
asociado con la distribución de los langostinos Heterocarpus hostilis y Nematocarcinus agassizii al norte
de los 4º30’S y con Benthesicymus tanneri al sur de
esta latitud, principalmente en profundidades mayores
a 800 m. La situación anterior difiere con lo reportado
para esta especie en la zona central de Chile, cuyo
rango batimétrico está entre 330 y 682 m, asociado a
camarón nailon (Heterocarpus reedi) y langostino
amarillo (Cervimunida johni) sometidos a explotación,
vulnerable a las redes de pesca de la flota arrastrera y
con creciente presencia en las capturas (Arana et al.,
2002, 2003).
En cuanto a la abundancia relativa de H. diomedeae, los valores descritos en esta investigación son
superiores a los indicados para los alrededores del
Banco de Máncora en 1996, (Kameya et al., 1997);
asimismo, mayores a los registrados para esta misma
área entre 1998 y 2002, cuyos valores no superaron
los 114 kg km-2, aunque ligeramente inferiores a los
reportados en 2003 (553 kg km-2), en que se incluyeron todos los langostinos y cangrejos (JDSTAIMARPE, 2004). Por otro lado, en la costa central de
Chile se han reportado densidades medias del orden de
552 y 714 kg km-2, y niveles de biomasa de ~645 ton
en un área de 1.159,8 km2 (Arana et al., 2003), superiores en densidad media e inferiores al nivel de biomasa total observado en este estudio.
El límite superior del rango de tallas y la talla media de H. diomedeae en ambos sexos, obtenidos en
este estudio, fueron superiores a los anteriormente
señalados para Perú (Méndez, 1981; Kameya et al.,
1997), resaltando la existencia de langostinos de mayor talla a profundidades mayores a 1.000 m. Sin embargo, coinciden en la distribución polimodal de las
frecuencias de tallas, con el grupo modal predominante de ~30 mm para hembras y ~27 mm para machos.
En relación a la estructura de tallas observada en Chile
(Arana et al., 2002, 2003, 2006), aunque se presentan
rangos de tallas similares, las tallas medias para Perú
son superiores tanto en machos como hembras (en este
estudio); asimismo, es notorio que la estructura demográfica del stock del centro de Chile muestra escasa
presencia de los grupos modales de tallas mayores,
evidencia del efecto de la actividad pesquera que
muestra una disminución paulatina de las tallas medias
en las capturas en las principales zonas de pesca
(SUBPESCA, 2004).
Los aportes al conocimiento de la biología de esta
especie en el Perú son escasos y principalmente han
enfatizado las relaciones talla-peso (Méndez, 1981;
Kameya et al., 1997), cuyos resultados son similares a
los mostrados en este trabajo. Mayores contribuciones
se han realizado en Chile, destacando la evidencia de
dimorfismo sexual en estructura por tallas o grupos
modales (confirmados en este estudio), parámetros de
crecimiento individual y talla de madurez gonadal
establecido para machos en 32,5 mm y 36,5-37,5 mm
para hembras (Arana et al., 2002, 2003).
En las zonas batial y arquibentónica de Perú se han
identificado 247 especies de peces y 284 de invertebrados, cuyo grado de diversidad está asociado a la
profundidad, con el más alto valor entre 500 y 1.000
m y en menor escala entre 1.000 y 1.500 m (Kameya
et al., 2006b), zona donde se encontró la mayor abundancia de H. diomedeae. Esta situación permite prever
que el ejercicio de cualquier actividad pesquera con
redes de arrastre o artes de pesca poco selectivos en
estas áreas orientadas a la pesquería del langostino
rojo de profundidad, afectaría notablemente a un alto
número de especies de peces e invertebrados que cohabitan con éste, las que serían capturadas como pesca
incidental y probablemente descartadas, con los subsecuentes efectos sobre la biocenosis batial y arquibentónica de Perú.
Siendo prioritaria para Perú la necesidad de identificar especies con potencial pesquero, que permitan
satisfacer la demanda pesquera nacional e internacional, crear oportunidades de empleo, estimular la inversión pesquera y proveer pesquerías alternativas ante el
decrecimiento de las pesquerías tradicionales (Kameya
et al., 2006a), las especies de langostinos de profundidad, principalmente la gamba roja H. diomedeae, se
perfilan con un importante potencial, no sólo por su
disponibilidad sino por su apreciada demanda comercial. Los resultados de este trabajo ponen a disposición
de la comunidad científica y pesquera nacional e internacional información reciente sobre distribución,
disponibilidad, estructura poblacional y abundancia
relativa de esta especie. Sin embargo, se estima prudente advertir que la decisión de establecer una actividad pesquera sostenible, amerita el desarrollo de programas de investigación previos que enfaticen estudios de biología reproductiva, ecología trófica, crecimiento, dinámica poblacional, así como estudios de
rendimiento pesquero y selectividad, que provean
información para el manejo y administración pesquera
sostenible y responsable, con un enfoque ecosistémico
y que dinamice el sector pesquero y la economía del
país.
AGRADECIMIENTOS
A la Secretaría General del Mar de España y al Instituto del Mar del Perú, de cuyas campañas de investigación se extrajeron los datos necesarios para este estudio; así como al grupo científico español y peruano
que participó en los muestreos y análisis de datos. Al
Dr. Wilmer Carbajal, quien contribuyó con su revisión, críticas y aportes a la elaboración de este trabajo;
Asimismo, especial reconocimiento al Dr. Patricio
Arana de la Pontificia Universidad Católica de Valparaíso de Chile, quien estimuló y propició la publicación de este documento.
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Arana, P., M. Ahumada & A. Guerrero. 2003. Distribución y abundancia de la gamba Haliporoides diomedeae (Crustacea: Decapoda: Penaeidae) frente a la
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Received: 8 May 2009; Accepted: 18 August 2009
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380
Lat. Am. J. Aquat. Res., 37(3): 381-394,
2009
Reproductive
aspects of the Patagonian toothfish off southern Chile
381
Research Article
Reproductive aspects of the Patagonian toothfish (Dissostichus eleginoides)
off southern Chile
1
Patricio Arana1
ABSTRACT. We present the results for the reproductive biology of Patagonian toothfish (Dissostichus eleginoides) caught off southern Chile from January to March and June to November 2006. A total of 10,896 specimens were measured (55-220 cm total length, TL) and sexed (7,049 males, 64.7%; and 3,847 females, 35.3%).
Macroscopic observations showed that gonad maturation begins at 60 cm TL in both sexes, with an average
maturation size of 81 cm TL in males and 89 cm TL in females. This species appears to have an ample spawning period that occurs only off the far southern region of Chile. To date, no evidence indicates that this resource reproduces in any other areas of the Pacific Ocean off the coasts of South America, where no specimens were observed with mature gonads, percentages of atresia were high, and juvenile fish were not caught
in trawl fishing operations targeting other commercial species.
Keywords: size structure, reproduction, size at first maturity, Patagonian toothfish, Dissostichus eleginoides,
Chile.
Aspectos reproductivos del bacalao de profundidad (Dissostichus eleginoides)
en el extremo austral de Chile
RESUMEN. Se dan a conocer resultados sobre la biología reproductiva del bacalao de profundidad (Dissostichus eleginoides) capturado en el extremo sur-austral de Chile, entre enero y marzo y de junio a noviembre de
2006. En dicho período se midió y determinó el sexo a 10.896 ejemplares, comprendidos entre 55 y 220 cm de
longitud total (LT), de los cuales 7.049 correspondieron a machos (64,7%) y 3.847 a hembras (35,3%). Mediante la observación macroscópica de las gónadas se determinó que en machos y hembras se observa el comienzo de la maduración gonádica a partir de 60 cm de LT, con una talla media de maduración (TMS50%) en
machos a 81 cm y en hembras a 89 cm. Se sugiere que esta especie presenta un período amplio de desove y
que este proceso se efectuaría únicamente en la región austral de Chile, destacándose que hasta ahora no se
cuenta con evidencias que este recurso se reproduzca en otra zona del océano Pacífico frente a la costa de Sudamérica en atención a la ausencia de ejemplares maduros en las capturas, altos porcentajes de atresia y ausencia de peces juveniles en faenas de pesca de arrastre dirigidas a otras especies comerciales.
Palabras clave: estructura de tallas, reproducción, talla de primera madurez sexual, bacalao de profundidad,
Dissostichus eleginoides, Chile.
________________________
Corresponding author: P. Arana ([email protected])
INTRODUCTION
The Patagonian toothfish (Dissostichus eleginoides
Smith, 1898) is a demersal species distributed in the
southern hemisphere, mainly between 40º and 60ºS
and at depths of 500 to 2000 m. Most catches of this
resource occur on the continental shelf off the southern cone of South America and around numerous
382
islands and oceanic elevations in the southern sectors
of the Atlantic, Pacific, and Indian oceans (Gon &
Heemstra, 1990). The high fishery yields and the elevated price that Patagonian toothfish brings on international markets have awoken greater interest in extracting and commercializing its meat.
In Chile, D. eleginoides is an important resource
for industrial and artisanal fishing. Thus, it has been
subjected to intense exploitation over a long period of
time. This situation is worrisome, especially since this
is a slow-growing species. In order to adapt the management measures intended to conserve this resource,
we must understand its reproductive cycle and particularly its size at first sexual maturity. Previous studies
have shown that this fish is a synchronous spawner
(also known as a total or isochronal spawner), with
two groups of different sized ovocytes; the larger diameter group is released during the first spawning
(Young et al., 1999). D. eleginoides spawns in the
southern part of the country in winter, mainly between
July and August, presenting low fecundity in relation
to its body weight (10-24 eggs per gram of weight)
(Young et al., 1995). This agrees with that indicated
by Agnew et al. (1999) for South Georgia Island.
These authors observed massive spawning in
July/August and suggested that a second, less intense
spawning period occurs in April/May. Arana & Bustos
(2006) detected a high percentage of specimens in an
advanced state of maturity during experimental fishing
operations for D. eleginoides off far-southern Chile in
the second half of September and first half of October
2005.
Given the uncertainty as to the spawning zones and
periods of the Patagonian toothfish south of 50°S and
the importance of understanding this species’ reproductive aspects for its adequate management, the present investigation set out to define the stock composition, reproductive period, and size at first sexual maturity for these fish, especially including the months in
which this species is under a reproductive ban.
The information analyzed was gathered on board a
longline factory vessel during two commercial fishing
campaigns: one from 01 January to 25 March 2006
and another from 17 June to 10 November 2006, totaling 130 days of operation. The extractive operations
were carried out of far-southern Chile, between
49°49’S and 59°39’S (Fig. 1). From a bathymetric
point of view, the hauls were done between 600 and
2,393 m depth.
The extractive operations were done with Spanishtype or “quebrado” longlines and size 9 hooks, those
commonly used by the industrial fleet (Guerrero &
Arana, 2009). The South American pilchard or “sardina” (Sardinops sagax) was used as bait.
For each fishing haul, random measurements were
made of a certain number of Patagonian toothfish
according to their arrival on the processing deck. The
total length (TL) of each individual was measured
with an ichthyometer (± 1 cm) and the total weight
using a scale precise to ±10 g. At the same time, we
determined the sex and state of maturity of the specimens through a visual, macroscopic examination of
the gonads according to the scale proposed by Kock &
Kellerman (1991) for Antarctic fishes (Table 1).
Based on the information recorded, we determined
the global sexual proportion and estimated the average
and median sizes, variance, and standard deviations.
In order to establish the composition of the catches for
each sex, the size records were grouped by trimesters
and the corresponding size frequency distributions
were constructed. Likewise, we determined the sexual
proportion by size based on the number of males
caught as compared to all the specimens
(males+females) in each length range.
The size at first sexual maturity (TMS50%) was determined separately for males and females according
to the percentage of specimens that presented mature
sexual organs with respect to the total of specimens
analyzed. The records were grouped every two centimeters in order to increase the number of observations
in each length range. Individuals were considered to
be mature at maturity stage 3 or higher (Everson &
Murray, 1999; Young et al., 1999).
The fit of the percentages of mature specimens vs.
the size of the specimens was done using two procedures. In the first, the model parameters were estimated using the linearization of the logistic function:
% M̂ ad LT =
1
1 + exp
( − a − b LT )
through which it is possible to estimate
TMS50% = -a/ b
s(TMS50%) = 1/ b
where:
%Mad TL
: proportion of mature specimens at
length TL (cm)
a, b
: model parameters
TL
: total length (cm)
TMS50%
: size at first sexual maturity of 50%
s(TMS50%) : standard deviation of the TMS50%
383
Reproductive aspects of the Patagonian toothfish off southern Chile
Figure 1. Area of Dissostichus eleginoides extraction operations.
Figura 1. Lugares de captura de los ejemplares analizados de Dissostichus eleginoides.
Table 1. Maturity scales based on ovarian and testis cycles in Notothenia coriiceps, Champsocephalus gunnari, Chaenocephalus aceratus and Pseudochaenichthys georgianus (from Kock & Kellerman, 1991).
Tabla 1. Escala de madurez basada en ciclos de ovarios y testículos de Notothenia coriiceps, Champsocephalus gunnari,
Chaenocephalus aceratus y Pseudochaenichthys georgianus (Kock & Kellerman, 1991).
Female
Maturity Stage
Males
Ovary small, firm, no eggs visible to the
naked eye
1
Inmature
Ovary more extended, firm, small oocytes
visible, giving ovary a grainy appearance
2
Developing or
resting
3
Developed
Testis small, translucent, whitish, long,
thin strips lying close to the vertebral
column
Testis white, flat, convoluted, easily
visible to the naked eye,
about 1/4 length of the body cavity
Testis large, white and onvoluted, no
milt produced when pressed or cut
4
Ripe
5
Shrunk
Testis large, opalescent white, drops of
milt produced when pressed or cut
Testis shrunk, flabby, dirty white in
colour
Ovary large, starting to swell the body
cavity, colour varies according to species,
contains oocytes of two sizes
Ovary large, filling or swelling the body
cavity, when opened large ova spill out
Ovary shrunken, flaccid, contains a few
residual eggs and many small ova
384
In the second procedure, the fit was made using the
non-linear least squares routine, considering the
Gauss-Newton method. The model was coded in MatLab language (v6.5) and solved using the function
nlinfit.m, which, along with the resolved parameters,
provided the vector of residuals and the “Jacobian”
matrix of first-order partial derivatives, that is:
⎛ ∂% Mad LT ( a ,b , LT ) ∂% Mad LT f ( a ,b , LT ) ⎞
,
J =⎜
⎟
∂a
∂b
⎠
⎝
where Mad LT corresponds to the logistic models of
sexual maturity at size TL.
The variance-covariance matrix for the parameters
was obtained with the equation:
n
males and females. The percentages of mature individuals based on size (stages ≥ 3) showed the usual
sigmoid form; the fit of these values was adequate
with both procedures used (Fig. 5). The linear and
non-linear fits (Table 3) showed an average size of
maturity (TMS50%) of 81 cm in males and 89 cm TL in
females.
Likewise, the maturity ogives show that not all the
fish over the TMS50% spawned. Only 90% of the
males measuring 95 cm TL or more reproduced. Although this situation was not as notorious for females,
nonetheless, not all specimens over 110 cm TL
spawned.
∑(% M̂ad LT − % Mad LT )2
DISCUSSION
n− p
Fish reproduction studies that determine size at first
sexual maturity and the place, period, and duration of
spawning make a necessary contribution, both from a
scientific point of view and to fishery management
especially for exploited species. In the particular case
of the Patagonian toothfish, both aspects are relevant
given the high longevity and slow growth of the species, plus the heavy fishing pressure to which it has
been subjected, indicating that this resource is highly
vulnerable to extreme situations.
The high percentage females in maturity stage 3
and of both sexes in this and higher maturity stages in
June and July indicate that the Patagonian toothfish
spawns in these months (Fig. 4). Nonetheless, the high
percentages of specimens in the post-spawning stage
in the other months considered herein indicate that this
species has a broad reproductive period. Despite this,
the lack of information from the months prior to and
following the analyzed periods impedes a more precise determination of the lapse in which the maximum
release of sexual products occurs.
As for size at first sexual maturity, the TMS50%
values for males (81 cm TL) and females (89 cm TL)
fall within the general range estimated by other authors (Table 4). The results for the females are similar
to those presented by Moreno (1998), Prenski &
Almeida (2000), Laptikhovsky & Brickle (2005), and
Shust & Kozlov (2006); whereas the males’ results
resemble the TMS50% values presented by CCRVMA
(1997), Everson & Murray (1999), Prenski & Almeida
(2000), and Laptikhovsky & Brickle (2005). In all
cases, the larger mature size of the females is evident.
According to the age estimates done by Oyarzún et al.
(2003), males mature at around nine years and the
females at around 11 years of age.
The lack of spawning in some fish larger than the
TMS50% is a phenomenon known for teleosts. A simi-
v = ( J ' J )−1 LT =1
where n is the number of observations and p is the
number of parameters. The standard error of each
parameter was obtained by taking the square root of
the elements that make up the diagonal of this matrix.
In this case, we determined the standard error and the
confidence range (95%) for the average value.
RESULTS
During the investigation, we analyzed a total of
10,896 individuals: 7,049 males and 3,847 females.
The males presented total lengths between 55 and 202
cm and the females between 55 and 220 cm (Fig. 2).
The average sizes of the specimens were similar in
January and July, when males averaged 104 to 113
mm TL and females 110 to 122.5 cm TL. In August,
however, the values decreased noticeably, remaining
more or less constant until November, with averagesizes of 88.5 to 98.4 mm TL for the males and 88.6 to
98.6 cm TL for the females.
The sexual proportion, except in August and November, was predominated by males (62.3-71.4%)
(Table 2). In terms of sexual proportion at size, in the
three trimesters examined, the males were predominant in number up to approximately 120 cm TL, after
which the proportion of females was greater (Fig. 3).
Between June and November (2006), we recorded
the gonad maturity stage of 6,160 individuals: 3,950
males and 2,210 females. In the period analyzed, a
high percentage of the specimens – both males and
females – showed developing gonads in June and July;
mature gonads from July to September, and spent
gonads from August to October (Fig. 4).
Our observation of the maturity stage of the gonads
revealed that maturation began as of 60 cm TL in both
Reproductive aspects of the Patagonian toothfish off southern Chile 385
Males
8
7
n= 2,542
Females
100
7
80
6
60
40
3
2
20
1
0
5
0
8
100
20
1
60
0
40
3
2
20
1
6
5
3
2
1
0
0
0
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
8
100
80
60
4
7
40
2
20
1
100
n= 1,325
80
6
5
60
40
3
2
20
1
0
0
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
20
0
0
0
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
0
8
7
n= 3,476
6
5
4
3
2
1
0
100
90
80
70
60
50
40
30
20
10
0
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
4
3
40
2
8
7
6
5
4
3
n= 3,738
100
80
60
40
2
1
0
20
0
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
Total length (cm)
Figure 2. Trimester size frequency and accumulated frequency distributions in Patagonian toothfish (Dissostichus eleginoides).
Figura 2. Distribuciones de frecuencias de tallas y frecuencia acumuladas trimestrales en bacalao de profundidad (Dissostichus eleginoides).
Sep - Nov
5
8
60
3
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
n= 2,413
6
5
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
100
90
80
70
60
50
40
30
20
10
0
n= 1,382
4
4
100
80
6
1
0
8
n= 3,682
4
40
2
7
80
5
7
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
n= 2,094
6
8
Jun -Aug
60
3
55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215
7
80
6
4
4
7
100
n= 1,140
Jan - Mar
5
8
Total
386
Table 2. Monthly sexual proportion, mean size, median size, and standard deviation in Patagonian toothfish caught off the far southern tip of Chile.
Tabla 2. Proporción sexual mensual, talla media, talla mediana y desviación estándar en bacalao de profundidad capturado en la región sur-austral de Chile.
Month
Monthly sexual
proportion
Range (cm)
Mean size (cm)
Median size (cm)
Standard deviation
(cm)
January
February
March
June
July
August
September
October
November
Males
62.3
68.6
71.4
67.6
59.6
41.2
68.5
59.4
49.4
Females
37.7
31.4
28.6
32.4
40.4
58.5
31.5
40.6
50.6
Males
80 - 138
57 - 169
59 - 192
58 - 202
57 - 159
58 - 152
55 - 156
56 - 144
59 - 132
Females
71 - 170
61 - 216
63 - 210
55 - 220
61 - 195
60 - 161
56 - 177
57 - 178
59 - 146
Total
71 - 170
57- 216
59 - 210
55 - 220
57 - 195
58 - 161
55 - 177
56 - 178
59 - 146
Males
104.2
107.6
110.6
106.9
113.7
88.9
92.3
98.4
88.5
Females
109.9
118.1
119.4
122.5
110.1
94.5
92.5
98.9
88.8
Total
106-4
111.0
113.1
111.9
114.7
92.2
92.4
98.6
88.6
Males
101.0
107.0
109.0
105.0
112.9
90.0
90.0
99.0
86.0
Females
102.5
117.0
117.0
120.0
109.2
89.5
87.0
96.0
86.0
Total
101.0
110.0
110.0
109.0
113.2
90.0
90.0
99.0
86.0
Males
12.6
16.8
17.4
16.8
20.3
17.2
16.6
16.8
14.2
Females
26.8
26.5
27.5
26.6
26.5
23.3
20.5
22.2
16.1
Total
19.5
21.0
21.2
21.8
23.6
21.2
17.9
19.2
15.2
Figure 3. Sexual proportion at size in Patagonian toothfish .
Figura 3. Proporción sexual a la talla en bacalao de profundidad.
lar situation was described by Everson & Murray
(1999) for this same species around South Georgia
Island, where up to 43% of the sampled females did
not spawn. It is reasonable to expect a certain percentage of atresia in large-sized females. Moreover, this
situation can be found in species with extended reproductive periods, so that, at any given moment, it is
possible to find spawning and spent individuals.
During the spawning period, females have been reported to emerge to shallower waters (400 a 500 m),
making it hard to find them in the commercial fishery
operations carried out at greater depths (Chikov &
Melnikov, 1990; Kock & Kellerman, 1991; Young et
al., 1999). This fact explains, at least partially, the
predominance of males in the catches in most of the
months analyzed, although the low proportion of females could also indicate an actual different propor-
387
tion between the sexes or that the females are less
attracted to the bait used in the fishing gear.
This study allowed us to gather information on the
reproductive process during the period of the reproductive ban decreed by the fishery authority for this
resource between 53°S and 57°S, recognizing the
occurrence of this process in the region. Nevertheless,
the specimens caught in this period presented evidence
of a progressive development of gonad maturity that
spanned practically the entire lapse analyzed. This
evidence indicates that the reproductive period of
Patagonian toothfish is broader than that considered so
far, with a certain number of mature specimens even
in the second half of the year (June to November
2006). In the samples analyzed in October-November
from far-southern Chile, when handling the specimens
for purposes of registering their total length and sex, it
was possible to induce ejaculation in males by palpating or placing slight pressure on the abdomen; the
same occurred with females, which released massive
amounts of eggs when slight pressure was applied to
their abdomens (Figs. 6 to 8).
Our results confirm that the Patagonian toothfish
reproduces in the southern region of Chile and that the
spawning period extends, partially or totally, to the
last trimester of the year. Likewise, these results show
the need to use the sizes determined herein as the
TMS50% rather than those values that attribute sexual
maturity to much larger sizes. This possible overestimation of lengths could be due to the analysis of small
samples in periods of scant reproductive activity or the
omission of small-sized specimens from the study.
According to the available evidence, this resource
does not reproduce off Chilean coasts north of 50°S,
despite being present in the deep waters of this oceanic sector. Several studies done off north and central
Chile verify this, mentioning the presence of specimens considered to be “maturing”. Thus, for example,
the microscopic analyses and gonadosomatic indexes
determined by Oliva et al. (1999) for the fish caught in
the far north of the country during an annual cycle did
not reveal a seasonal pattern; thus, these authors could
not identify a possible spawning period. The same was
found first by Martínez (1975) and then by Young et
al. (1999), who noted no mature individuals in the
north and central-south zones; rather, 95.6% and
99.7% of the males in these areas had “immature”
testicles. Moreover, an important percentage of the
females presented folicular atresia: on average, 82.0%
in the north and 54.3% in the south (Young et al.,
1999). More recently, Oyarzún et al. (2003) analyzed
the monthly variation of the gonadosomatic index
(GSI) calculated for samples of specimens landed at
Lebu (37°35`S) and Corral (39°53`S), reporting no
reproductive activity.
388
Males
Females
n = 502
100
80.5
80
60
40
20
6.2
12.4
1.0
0.0
4
5
0
1
2
3
n = 888
100
80
55.4
60
40
20
23.6
15.7
5.3
0.0
0
1
2
3
4
Percentage
80
60
38.7
40
30.2
21.7
20
6.6
2.8
0
1
2
3
4
80
60
42.1
40
20
29.7
11.3
14.0
2.9
0
1
2
3
4
80
51.7
60
40
20
26.5
12.7
2.4
6.7
0
1
2
3
4
100
90
80
70
60
50
40
30
20
10
0
66.9
16.1
15.7
1
2
100
90
80
70
60
50
40
30
20
10
0
5
1.2
0.0
4
5
45.2
34.4
14.7
4.8
2
0.9
3
4
5
n = 106
55.7
25.5
12.3
3.8
2.8
2
3
4
5
n = 755
33.9
31.1
23.3
7.7
4.0
1
100
90
80
70
60
50
40
30
20
10
0
3
n = 544
1
5
n = 804
100
n = 248
1
5
n = 1,650
100
100
90
80
70
60
50
40
30
20
10
0
5
n = 106
100
100
90
80
70
60
50
40
30
20
10
0
2
3
4
5
n = 557
37.2
32.9
16.2
12.4
1.4
1
2
3
4
5
Maturity stage
Figure 4. Maturity stage by sex and month in Patagonian toothfish (Dissostichus eleginoides).
Figura 4. Estados de madurez, por sexo y mes en bacalao de profundidad (Dissostichus eleginoides).
However, those individuals landed at Quellón (43°S),
but caught farther south, showed high GSI values.
Our results, and those of earlier studies, allow us to
conclude that D. eleginoides reproduces massively in
the far south of Chile. No similar situation has been
shown in other parts of the country, suggesting that
this resource does not reproduce off north and central
Chile. The Patagonian toothfish is known to be stratified by size according to depth, with juveniles found
in shallower strata than the adults; this is a defense
mechanism that allows the former to avoid being
preyed on by individuals of their own species. Despite
389
this, trawlers operating in diverse Chilean fisheries on
the continental shelf and upper slope to at least 500 m
depth have not reported catches of D. eleginoides
juveniles, strengthening the hypothesis that only
adults, displaced from rearing zones in far southern
Chile or from Atlantic sectors, are present in these
waters.
1,0
% Mad =
0,9
% mature females
0,8
a
1
1 + e (8.069 − 0.089 LT )
0,7
0,6
0,5
0,4
0,3
FEMALES
0,2
0,1
0,0
0
20
40
60
80
100
120
140
160
180
Total length (cm)
1,0
b
0,9
0,8
% mature males
The size range and average sizes determined for
Patagonian toothfish are generally found within the
margins determined previously for the region where
the present study was performed. Likewise, the average sizes reported herein agree with those established
for specimens extracted with longlines from the waters
around the Falkland/Malvinas Islands (Laptikhovsky
et al., 2006). Nevertheless, the change in the average
sizes found in the study area during the different
months is striking, possibly indicating differences in
the behavior of the resource or geographic or bathymetric displacements that reveal the arrival of largesized specimens in the first month of the year; in the
second semester, the average size declines, reflecting a
process of recruitment of smaller sizes or the displacement of larger sizes to areas where they are not
fished.
TMS50% = 89.89 cm
0,7
0,6
% Mad =
0,5
0,4
1
1 + e (8.379 − 0.103 LT )
0,3
MALES
0,2
TMS50% = 81.319 cm
0,1
0,0
0
20
40
60
80
100
120
140
160
180
Total length (cm)
Figure 5. Sexual maturity ogive in Patagonian toothfish
off southern region of Chile.
Figura 5. Ojiva de madurez sexual en bacalao de profundidad en la región sur-austral de Chile.
Table 3. Logistic function results of the fit the data of maturity.
Tabla 3. Resultado del ajuste de la función logística con los datos de madurez a la talla.
Fit
Linear
Non-linear
Sex
Parameter
a
b
TMS50%
TMS50% limits
lower upper
Females 8.069 0.089
89.89
86.4
93.4
Males
0.379 0.103
81.31
78.4
84.4
Females 7.864 0.089
88.84
87.15
90.54
Males
80.31
78.93
81.69
8.277 0.103
The rapid change in average sizes determined in
the three analyzed trimesters highlights the lower sizes
towards the end of the year and the corresponding
increment in the proportion of specimens that are
caught under the TMS50% (Table 5). This situation is
especially evident in the last trimester, when 47.5% of
the females caught were smaller than those at maturity. This situation is worrisome since the decreasing
sizes are due to extraction, which puts the conservation of the stock at risk.
An alternative explanation could be that the females are not attracted to the bait during certain pe-
riods or that they move away from the fishing areas
normally used by the fleet. Another option is that, in
the second semester, Patagonian toothfish come from
the Atlantic sector, possibly juveniles that are recruited to the Pacific population. This would produce
a progressive increment in the smaller size fraction
and, therefore, the reduction of the quantity of specimens over the TMS50% (Fig. 2, Table 5). The fishermen know to expect a sudden increment in yields in
the second half of September due to the apparent arrival of specimens from the Atlantic sector. Thus, they
prefer to postpone the onset of fishing for this species,
390
Table 4. Size at first sexual maturity (TMS50%) determined in Patagonian toothfish.
Tabla 4. Tallas de primera madurez sexual (TMS50%) determinadas en el bacalao de profundidad.
Geographic area
Total length (cm)
Author
Males
Females
Both sexes
75.7
110.4
-
CCRVMA (1997)
67
86
-
Moreno (1998)
78.5
98.2
-
Everson & Murray (1999)
75
101
-
Agnew et al. (1999)
-
-
100
65
80
-
63
85
86
96
-
Laptikhovsky & Bricckle (2005)
Argentina
76.3
87.1
-
Prenski & Almeyda (2000)
Chile
105
117
-
Moreno et al. (1997)
-
128.7
-
Young et al. (1999)
78-94
113-117
-
Oyarzún et al. (2003)
81
89
-
Present study
South Georgia Island (Subarea 48.3)
Head and MacDonald Islands
Kerguelen Islands
Falkland/Malvinas Islands
Constable et al. (1999)
Duhamel (1991)
Lord et al. (2006)
Figure 6. Female Dissostichus eleginoides gonad in an advanced stage of maturity.
Figura 6. Gónada de hembra de Dissostichus eleginoides en avanzado estado de madurez.
391
Figure 7. Ovas in a female Dissostichus eleginoides gonad.
Figura 7. Óvulos en gónada de hembra de Dissostichus eleginoides.
Table 5. Average size and weight of the specimens, and percentage of specimens under the size at first sexual maturity
per period for each sex.
Tabla 5. Talla y peso media de los ejemplares, y porcentaje de ejemplares bajo la talla de primera madurez sexual por
período en cada sexo.
Males
Females
n
Mean size
(cm)
Jan - Mar
2,542
109.0
8.3
6.1
1,140
118.5
17.7
14.6
Jun - Aug
2,094
103.1
7.1
12.3
1,382
111.2
15.0
25.9
Sep - Nov
2,413
93.7
5.4
27.8
1,325
94.2
8.0
47.5
Total
7,049
Period
Mean weight % below
(kg)
TMS50%
first filling quotas for other resources (e.g., southern
hake and pink cusk-eel).
The displacement of the Patagonian toothfish from
the far south of Chile or even from the Atlantic sector
towards lower latitudes, should be confirmed by tagging, a methodology that is being used successfully in
other regions where this species is found (e.g., Williams et al., 2002; Marlow et al., 2003; Agnew et al.,
2006). Along with the scientific contribution of such a
study in diverse biological aspects, it would allow us
to determine whether the Patagonian toothfish effec-
n
Mean size Mean weight % below
(cm)
(kg)
TMS50%
3,847
tively migrates northward along the western coast of
the South American continent. This, in conjunction
with the hypothesis (not yet proven with certainty)
that D. eleginoides does not reproduces north of 47°S,
would imply that these fish are only invaders, taking
advantage of oceanographic conditions similar to
those found in deeper waters. If this is so, it would
also help explain the progressive decline in the yields
off central and northern Chile, since the exploitation
of these fish in the south would decrease the possibility of finding them farther north.
392
Apablaza, Francisco Gallardo, Andrés Ruíz, Alejandro
Stack, and Guillermo Stack for helping with on-board
sampling operations.
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Figure 8. Gonad and ejaculation induced by pressure on
the abdomen of Dissostichus eleginoides male.
Figura 8. Gónada y eyaculación inducida por presión del
abdomen de machos de Dissostichus eleginoides
ACKNOWLEDGEMENTS
The authors thank Pesca Chile S.A. for the support
and facilities granted for carrying out the present research project. We also thank the crew and Mr. Pedro
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& J. Pearce. 1999. Depth distribution and spawning
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Received: 11 November 2008; Accepted: 19 August 2009
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394
Lat. Am. J. Aquat. Res., 37(3): 395-408, 2009
Demersal biomass and potential yield from southern Brazil
395
Research Article
Biomass and fishing potential yield of demersal resources from the outer shelf
and upper slope of southern Brazil
Manuel Haimovici¹, Luciano Gomes Fischer2, Carmem L.D.B.S. Rossi-Wongtschowski3,
Roberto Ávila Bernardes3 & Roberta Aguiar dos Santos4
1
Instituto de Oceanografia, Fundação Universidade Federal de Rio Grande, FURG
2
Pós Graduação em Oceanografía Biológica, FURG
3
Instituto Oceanográfico da Universidade de São Paulo, IOUSP
4
Instituto Chico Mendes, ICMBio, Ministério do Meio Ambiente
ABSTRACT. The relative abundance and fishing potential of the commercially valuable fishes and cephalopods with marketable size was assessed using two seasonal bottom trawl surveys performed in 2001 and 2002
on the outer shelf and upper slope (100-600 m depth) off the coast of southern Brazil. These surveys were part
of REVIZEE, a national program designed to assess the fishery potential within the Economic Exclusive Zone.
Of the 228 fish and cephalopod species caught during the surveys, only 27 species and genera were considered
to be of commercial interest. Commercial-sized individuals of these species made up 52.3% of the total catch.
The total biomass was estimated to be 167,193 ton (± 22%) and 165,460 ton (± 25%) in the winter-spring and
summer-autumn surveys, respectively. The most abundant species were the Argentine short-fin squid Illex argentinus, a species with highly variable recruitment, followed by the Argentine hake Merluccius hubbsi, the
gulf-hake Urophycis mystacea, and the monkfish Lophius gastrophysus. The latter three were intensively
fished prior to the surveys, as well as the beardfish Polymixia lowei and silvery John dory Zenopsis conchifera, both relatively abundant but with a very low market value. The potential yield of the demersal fish species, not considering Illex argentinus, estimated with the Gulland equation for a mean natural mortality of M =
0.31, was 20,460 ton. When considering only Merluccius hubbsi, Urophycis mystacea, and Lophius gastrophysus, the potential yield decreased to 6,625 ton. The surveys showed that the fishery potential of the outer
shelf and upper slope was substantially lower than that of the inner shelf. Therefore, this environment should
be carefully monitored to avoid overfishing and fast depletion.
Keywords: demersal fishes, stock assessment, biomass, Brazil.
Biomasa y rendimiento potencial pesquero de recursos demersales de la plataforma
externa y talud superior del sur de Brasil
RESUMEN. Se evaluó la abundancia relativa y el potencial pesquero de peces y cefalópodos de especies y
tamaños de valor comercial en dos muestreos estacionales con redes de arrastre de fondo realizados en los
años 2001 y 2002 sobre la plataforma externa y talud superior, 100 a 600 m de profundidad, a lo largo del extremo sur de la costa brasilera, como parte de un programa nacional de evaluación del potencial pesquero de la
Zona Económica Exclusiva (Programa REVIZEE). Del total de 228 especies de peces y cefalópodos capturados, sólo 27 especies y géneros fueron considerados de interés comercial. Los tamaños comercializables de estas especies representaron 52,3% de la captura total. La biomasa total estimada fue de 167.193 ton (± 22%) y
165.460 ton (± 25%) en los muestreos de invierno-primavera y verano-otoño respectivamente. Las especies
más abundantes fueron el calamar argentino Illex argentinus, especie de reclutamiento muy variable, seguido
de la merluza argentina Merluccius hubbsi, la brótola de profundidad Urophycis mystacea, el pez sapo o rapé
Lophius gastrophysus, estas últimas intensamente explotadas en la época de los levantamientos, así como también Polymixia lowei y Zenopsis conchifera, ambas relativamente abundantes pero de escaso valor comercial.
El rendimiento potencial de especies demersales excluido Illex argentinus, estimado a través de la ecuación de
Gulland para un coeficiente de mortalidad natural medio de M = 0,31, fue de 20.460 ton. Cuando sólo
396
Merluccius hubbsi, Urophycis mystacea y Lophius gastrophysus fueron considerados, el potencial disminuye a
6.625 ton. Los mustreos mostraron que el potencial pesquero de la plataforma continental externa y el talud
superior es substancialmente inferior al de la plataforma interna, por lo tanto, este ambiente debe ser cuidadosamente controlado para evitar la sobrepesca y rápida depleción.
Palabras clave: peces demersales, evaluación, biomasa Brasil.
________________________
Corresponding author: Manuel Haimovici ([email protected])
INTRODUCTION
Exploratory bottom trawl surveys provide important
information on the distribution and abundance of potential fish resources (Saville, 1977). Density estimates based on research surveys are subject to bias
due to several factors, including the gear and its rigging, trawl depth, time of day, distribution, fish behavior and size, and others (Gunderson, 1993). More
realistically, bottom trawl surveys produce relative
abundance indices rather than absolute estimates, and
potential yield must be carefully inferred. However, at
the initial stages of fishery development, such surveys
can be helpful, providing rough estimates of the biomass and the potential yield of the assessed resources
(Gulland, 1983).
Industrial fisheries in southern Brazil began in the
late 1940s following the same development pattern
observed worldwide in the second half of the 20th
century (Yesaki & Bager, 1975). For two decades,
bottom trawling expanded almost exclusively over the
inner shelf at depths under 100 m and it peaked in the
early 1970s (Haimovici et al., 1989; Valentini et al.,
1991). Due to the combination of new fishing technologies, cheap fuel, elevated fish abundances, and
increasing market demands, catches have decreased
steadily since then, despite increased efforts (Haimovici, 1998). Fishing on the outer shelf for demersal
fishes with bottom trawls or bottom gill-nets began off
the state of Rio Grande do Sul in the mid-1980s, targeting elasmobranches and flatfishes (Haimovici,
1997). In the late 1990s, this effort expanded along the
outer shelf off Santa Catarina State and, later, over the
entire southern region (Perez & Pezzuto, 2006). Intense fishing on the upper slope started soon after,
when large foreign fishing vessels with the capacity
for onboard processing and freezing were authorized
to fish on the upper slope (Perez et al., 2003).
It is possible to contextualize Brazilian exploratory
fishing by research vessels and the development of
commercial fisheries as follows: early exploratory
fishing to assess the demersal fishing potential on the
outer shelf and slope started in the 1950s and 1960s
onboard Portuguese, Japanese, and German research
vessels. In the 1970s, the national fishery agency
(SUDEPE), with support from the United Nations
agency (PNUD), developed a series of surveys with
large commercial bottom trawlers. These surveys were
continued in the 1980s with the research vessel Atlântico Sul of the Federal University of Rio Grande
(FURG). The main results of these surveys, including
unpublished reports, were summarized in Haimovici et
al. (2007). More recently, two seasonal bottom trawl
surveys were performed in 2001 and 2002 as part of
the Brazilian governmental program REVIZEE: Assessment of the Sustainable Yield of the Economic
Exclusive Zone (Haimovici et al., 2008).
This paper focuses on the distribution, relative
abundance, and fishing potential of the main commercially valuable species on the outer shelf and upper
slope of southern Brazil based on data obtained during
the REVIZEE surveys. These surveys coincided with
the rapid development of trawling and gillnet fishing
on the upper slope and provided useful data on the
distribution, seasonality, and yields of the demersal
fish resources vulnerable to such gears.
Study area
The study area included southern Brazil’s outer shelf
and slope between Cabo Frio (23°S) and Chui
(34°35’S) (Fig. 1). Along this area, the shelf width
ranged from 140 to 180 km, narrowed to 90 km along
Cabo de Santa Marta Grande (29ºS), attained a maximum width of 250 km along the southeastern Brazilian Bight, and narrowed again to 50 km in Cabo Frio.
The area encompassed by the 100 to 600 m isobaths
covered 152,354 km2 (Table 1). Bottom sediments on
the outer shelf were mostly mud rich in silts and clay,
although large patches with biodetritic sediments and
sand were found near the shelf break and along Cabo
Frio; on the slope, muddy sediments were dominant
(Martins et al., 1976; Figueiredo & Madureira, 2004).
The most remarkable hydrographic characteristics on
the shelf were the seasonal variation of the water temperature and water column stratification, which was
strong in summer and weak or non-existent in winter
(Castro & Miranda, 1998). Another important feature
397
Figure 1. The study area and haul positions in the REVIZEE trawl surveys along the outer shelf and upper slope in southern Brazil.
Figura 1. Área de estudio y posición de los arrastres en el levantamiento pesquero del programa REVIZEE realizado en
la plataforma externa y talud superior del sur de Brasil.
Table 1. Areas and number of hauls at each depth and latitude stratum in the REVIZEE bottom trawl surveys on the outer
shelf and upper slope in southern Brazil (2001-2002) in winter-spring (w-s) and summer-autumn (s-a).
Tabla 1. Áreas y número de lances en cada estrato de profundidad y latitud en los muestreos pesqueros de arrastre de
fondo del Programa REVIZEE realizados en la plataforma externa y talud superior del sur de Brasil (2001-2002) in invierno-primavera (w-s) y verano-otoño (s-a).
Stratum
A (Chuí – Conceição)
B (Conceição - Santa
Marta Grande)
34°35'S - 31°30'S
31°30'S - 28°00'S
Areas
Depth (m)
2
Hauls
Areas
2
Hauls
C (Santa Marta Grande D (Ilha Bela - Cabo Frio)
Ilha Bela)
28°00'S - 24°24'S
Areas
2
24°24'S - 23°00'S
Hauls
Areas
2
Hauls
km
w-s
s-a
km
w-s
s-a
km
w-s
s-a
km
w-s
s-a
100-149
7,524
6
5
16,723
8
9
17,124
6
4
14,961
5
6
150-199
7,869
4
4
15,284
4
3
20,354
6
4
8,110
2
5
200-299
2,237
5
4
6,456
7
6
5,762
4
3
3,121
3
2
300-399
1,247
5
4
3,460
3
4
2,450
4
5
1,857
1
6
400-600
3,340
10
10
6,529
6
6
5,141
15
11
2,805
9
10
Total
22,217
30
27
48,452
28
28
50,830
35
27
30,855
20
29
398
at latitudes over 30ºS was a shelf front that shifted
northward in the cold season and southward in the
warm months, separating the cold, less salty
Subantarctic Surface Waters of the shelf from the
warmer, saltier Shelf Subtropical Waters (Piola et al.,
2000). On the upper slope, the Brazil Current ran
southward in the upper layers and the Malvinas Current ran northward, meeting at a front that shifted
seasonally in the north-south direction and was known
as the western boundary of the Subtropical Convergence. Beneath the Brazil Current, the South Atlantic
Central Waters (SACW) had temperatures between
10ºC and 17ºC and, below these, between 400 and 600
m, a mixture of SACW and Antarctic Intermediate
Waters were found with bottom temperatures ranging
from 4ºC to 10ºC.
Vessels and gears
Due to the large extension of the area under investigation, two research vessels were used: the R/V Soloncy
Moura (26 m, 600 HP) from the Brazilian Environmental Agency (IBAMA) and the R/V Atlântico Sul
(39.5 m, 860 HP) from the Federal University of Rio
Grande (FURG).
Both vessels were geared with Engel Star Ballon
trawl nets with 439 meshes of 160 mm stretched between opposite knots in the mouth and 27 mm in the
codend. The groundrope had a “rockhopper” of rubber
discs (300, 200, and 130 mm in diameter) in its central
20.8 m with two lateral extensions of 9.8 m each;
considering the 75 mm rubber discs, this totalled 40.4
m. The otter doors (550 kg rectangular Engel Hydro)
were connected to the wings of the net by 5-m-long
lengthening bridles and to the winch cables with 50-m
bridles. These nets were similar to those used in commercial fishing on the upper slope by otter trawlers,
although the mesh size in the codend was smaller in
this study.
Sampling
The surveys were performed almost simultaneously,
with the R/V Atlântico Sul operating from August to
September 2001 and March to April 2002 between
28ºS and 34º35’S, and the R/V Soloncy Moura cruising from August to October 2001 and from February
to April and in late June 2002 between 23ºS and 28ºS.
Overall, 224 effective fishing hauls were performed
between Cabo Frio and Chuí at depths between the
100 m and 600 m isobaths: 113 hauls were done in
winter and spring 2001 and 2002 and 111 in summer
and autumn 2002 (Table 1). After each tow, the fishes
and cephalopods in the catch were classified, counted,
and weighed. For large catches, random samples of 30
kg of small fish and cephalopods were classified and
the number and weight of each species was recorded.
For most of the tows, the length composition of the
samples of all the species was also recorded. The total
catch in number and weight and the mean weight for
each haul was calculated for all species (Haimovici et
al., 2008).
The main scope of the surveys was to study the
distribution and abundance of the whole fish fauna
vulnerable to bottom trawls without much previous
knowledge about the distribution pattern of each species (Haimovici et al., 2008). In this situation, systematic sampling was recommended to cover the whole
study area (Saville, 1977; Gunderson, 1993); this was
done by distributing the fishing stations along profiles
perpendicular to the coastline, 55 miles apart and in
depth ranges of 100-149, 150-199, 200-299, 300-399,
and 400-600 m. Some depth ranges were not well
represented along the profiles with sharp slopes,
whereas additional stations were included to better
represent larger areas in depth ranges with milder
slopes. For the biomass analysis, hauls were grouped
into four latitudinal areas named A to D from south to
north (Fig. 1). Combining latitudinal and depth ranges,
20 strata were defined (Table 1). The surface of each
stratum was calculated graphically with ArcView 3.2
Software, integrating the polygons determined by the
latitudinal transects and isobaths obtained from the
GEBCO (General Bathymetric Chart of the Oceans)
database (http://www.gebco.net) and complemented
with data from acoustic surveys of the REVIZEE Program (Madureira et al., 2005).
Since the codends of the nets used for the bottom
trawl surveys had smaller mesh than those used in
commercial fishing, the samples included fishes
weighing less than the minimum marketable weight
(MMW). The MMW values for the main species in
the catch were obtained from the literature or personal
communications (Table 2). As the scope of this paper
is to estimate the commercial biomass and potential
yield for each of the main species, only hauls in which
the mean weight was over the MMW were included.
This assumption was necessary because the size composition of all species for all hauls was not always
available. Preliminary tests showed that the hauls in
which the mean weight was under the MMW had a
very small fraction in weight over the MMW and
those in which the mean weight was over the MMW
had only a small fraction of the catch smaller than the
marketable size.
Density and biomass estimates
Densities were calculated as catch per unit of areas
(CPUA) in kg km-2. The swept areas were estimated
by multiplying the distances between the beginning
and the end of the hauls recorded by the satellite posi-
399
Table 2. Minimum marketable individual weight (MMW) and minimum marketable total length or mantle length
(MMTL) of the main commercially important species caught in the REVIZEE bottom trawl surveys on the outer-shelf and
upper-slope in southern Brazil (2001-2002).
Tabla 2. Peso mínimo de peces y calamares con valor comercial (MMW) y peso mínimo largo total o del manto (MMTL)
de las principales especies capturadas en los muestreos de arrastre de fondo del Programa REVIZEE en la plataforma
externa y talud superior del sur de Brasil (2001-2002).
MMW MMTL
Reference
(g)
(mm)
% of hauls with mean
weight over MMW
Species
Illex argentinus
83
100
180
Haimovici et al. (2006a)
Urophycis mystacea
98
100
250
Haimovici et al. (2006b)
Merluccius hubbsi
85
100
250
Haimovici et al. (1993)
Lophius gastrophysus
100
350
290
Haimovici (pers. observ.)
Zenopsis conchifera
67
350
280
Haimovici (pers. observ.)
Polymixia lowei
91
100
200
Rossi-Wongtschowski (pers. observ.)
tioning system and the width of the swept area calculated as 18.18 m or 45% of the length of the groundrope based on Alverson & Pereyra (1969). Geometry
and net gearing, towing speed, and fish behavior can
affect catchability (q); since none of these effects
could be measured, a value of 1 was attributed to q as
suggested by Alverson & Pereyra (1969) and Fogarty
(1985).
The mean densities (kg km-2) Di of each species i
in each survey were calculated by weighing the mean
densities in each stratum by the fraction of the total
area of each stratum Ae (eq. 1). The variances of the
mean density of each species in each stratum S D2
i
were calculated by weighing the variances in each
stratum SDie divided by the number of samples and
multiplied by the square of the fraction of the area of
each stratum (eq. 2).
Di =
S2 =
Di
∑e Die ⎛⎜⎝ AAe ⎞⎟⎠
∑
e
(1)
2
S2
Die ⎛ A e ⎞
⎟
⎜
n e ⎜⎝ A ⎟⎠
(2)
The biomass of each species in each survey was
calculated as the sum of the products of the densities
for the areas of all strata (eq. 3), and the total variances were calculated by multiplying the variances in
each stratum by the respective squared areas.
e
Bi =
∑A
1
e D i.e
(3)
e
var Bi =
∑A
2 2
e SDie
(4)
1
The 90% confidence intervals of the biomass estimates were calculated based on Student’s “t” distribution for α = 0.1 and v degrees of freedom (Zar, 1984)
according to equations (5) and (6).
2
ICα% = Bi ± tα,ν SD
(5)
ν = ∑ ( ne − 1)
(6)
ie
e
Potential yield
Potential yield was calculated under the assumption
that the maximum growth in mass of a population
occurs at intermediate levels of abundance and is related to the population’s natural mortality. In its simplest form, populations can be assumed to grow following a logistic model in which maximum growth
occurs when the biomass halves the virginal biomass
(B∞) and fishing mortality (F) equals the natural mortality (M) (Graham, 1935). Provided unbiased estimates of virginal biomass and natural mortality are
available, an approximation of the maximum equilibrium yield (Ymax) can be calculated by the formula
Ymax= M (X B∞) (Gulland, 1971). The value of 0.5 for
X, originally proposed by Gulland, was considered to
be too high for most long-living species (Beddington
& Cooke, 1983; Walters & Martell, 2002); thus, we
used a value of 0.4 in our calculations.
Natural mortality was calculated separately for
each of the five most abundant commercially valuable
fishes; this was inferred from the longevity equation
400
proposed by Hoenig (1983) based on longevity estimated from growth studies (Table 3). A common
value of M = 0.31 was calculated, weighing M estimates for each species or group of species by its contribution in weight to the catch of those species.
excluded, the winter-spring biomass was 16% higher
(158,281 ton) than the biomass estimated during the
summer-autumn survey (136,813 ton). In the winterspring survey, bony fishes were 13% and elasmobranches 26% more abundant than in the summerautumn survey (Table 5).
The total biomass of commercial sizes of marketable species was calculated by depth and latitude
strata in both seasons (Fig. 2). On the outer shelf,
biomass decreased from higher to lower latitudes in
both surveys; elasmobranches were more abundant in
the south (areas A and B), where commercial-sized
Illex argentinus were absent. On the upper slope, biomass was higher in the central areas (B and C) in winter-spring and, in area B, in summer-autumn, and both
bony fish and I. argentinus biomasses were larger.
Elasmobranches were more abundant on the outer
shelf than on the upper slope and in the southern area
of the study.
Overall density was 27% higher in the summerautumn survey. On the outer shelf, it was much higher
in the south, particularly in winter-spring. On the upper slope, the difference was smaller but densities
were still higher in the south. Both biomass and densities of commercially valuable fishes from the outer
shelf were lower than those on the upper slope (Table
6).
RESULTS
The list of fishes and cephalopods caught in the
REVIZEE bottom trawl surveys off southern Brazil
included 228 species (Haimovici et al., 2008); few of
them were of commercial interest. To select those
species, we examined the marine fisheries landing
reports for the southern states of Brazil (IBAMA,
2007). We also examined the literature and databases
such as FISHBASE (Froese & Pauly, 2009) to find
additional species that are commercially fished in
other regions. This filtering resulted in 27 species and
genera of interest (Table 4).
The overall catch from both surveys was 32,715
kg, and the total catch of the 27 selected species was
24,946.3 kg (76.5%), 17,418 kg (52.9%) of which
complied with the adopted size selection criteria (Table 4). Six species (Illex argentinus, Urophycis mystacea, Merluccius hubbsi, Polymixia lowei, Zenopsis
conchifera, Lophius gastrophysus) accounted for
77.8% of the catch with commercial value; another
9.8% consisted of other bony fishes and 12.4% were
cartilaginous fishes.
The total biomass of commercial sizes for marketable species was estimated to be 167,193 ton (± 22%)
in the winter-spring survey and 165,460 ton (± 25%)
in the summer-autumn survey. However, if squids are
Illex argentinus
The mean mantle length of the Argentine short-fin
squid Illex argentinus landed by commercial fishing
was over 160 mm for males and 180 mm for females
(Haimovici et al., 2006a), corresponding to approximately 100 g. In the surveys, 83% (in weight) of the
Table 3 Hoenig (1983) equation-based estimates of the natural mortalities of the main commercially important species
caught in the REVIZEE bottom trawl surveys on the outer-shelf and upper-slope in southern Brazil (2001-2002). Other
fishes include Elasmobranchii, Sciaenidae and Paralichthyidae.
Tabla 3. Mortalidad natural, estimada mediante la ecuación de Hoenig (1983), de las principales especies de interés comercial capturadas en los muestreos de arrastre de fondo del programa REVIZEE en la plataforma externa y talud superior del sur de Brasil (2001-2002). “Other fishes” incluye Elasmobranchii, Sciaenidae and Paralichthyidae.
% of the
catch
Maximum
age
Mortality
estimate
Urophycis mystacea
9
14
0.30
Haimovici et al. (2006b)
Merluccius hubbsi
17
12
0.35
Vaz-dos-Santos & Rossi-Wongtschowski (2005)
7
18
0.23
Lopes (2005)
Zenopsis conchifera
19
15
0.28
Duarte-Pereira et al. (2005)
Polymixia lowei
25
10
0.42
Rossi-Wongtschowski (pers. observ.)
Other fishes
23
10 - 40
0.20
Species
Reference for maximum age
Table 4. Total catch and catch in hauls with mean weight
over minimum marketable weight (MMW) of the commercially valuable species in the REVIZEE bottom trawl
surveys on the outer shelf and upper slope in southern
Brazil (2001-2002).
Tabla 4. Captura total y en los lances en los cuales el
peso medio fue superior al menor peso comercializable
(MMW) de las especies de interés comercial en los levantamientos pesqueros del programa REVIZEE realizados en la plataforma externa y talud superior del sur de
Brasil (2001-2002).
Under
MMW
(kg)
Over
MMW
(kg)
383
1,240
411
24
0
51
26
145
1,734
3
178
996
536
479
341
175
118
7,796
3,445
2,553
2,316
1,292
1,113
651
430
230
169
163
58
0
0
0
0
0
139
0
19.8
14.7
13.3
7.4
6.4
3.7
2.5
1.3
1.0
0.9
0.3
0.0
0.0
0.0
0.0
0.0
0.8
0.0
0
0
0
39
23
0
0
0
0
461
390
349
167
152
165
156
147
32
2.6
2.2
2.0
1.0
0.9
0.9
0.9
0.8
0.2
% of total
catch
Teleosts
Polymixia lowei
Zenopsis conchifera
Merluccius hubbsi
Urophycis mystacea
Umbrina canosai
Prionotus punctatus
Paralichthys isosceles
Trichiurus lepturus
Genypterus brasiliensis
Beryx splendens
Helicolenus lahillei
Trachurus lathami
Ariomma bondi
Thyrsitops lepidopoides
Loligo plei
Mullus argentinae
Other teleosts
Elasmobranches
Atlantoraja cyclophora
Atlantoraja platana
Squalus mitsukurii
Squalus megalops
Mustelus schmitti
Atlantoraja castelnaui
Squatina argentina
Squatina guggenheim
Squatina punctata
Cephalopods
Illex argentinus
Total
598
2,841
16.3
15,297
17,418
100.0
401
squids caught were over this size (Table 5). In the
winter-spring survey, commercial-sized squids were
concentrated between Solidão and Cabo de Santa
Marta Grande at over 400 m depth, with an estimated
biomass of 8,912 ton (± 106%). In summer-autumn,
squid biomass increased sharply to 28,647 ton (±
62%) and larger densities were found in the 300 to
600 m depth range between Chuí and Cabo de Santa
Marta Grande (Fig. 2). Specimens under the commercial size occurred mainly in the upper 300 m (Haimovici et al., 2008). Wide confidence intervals for the
biomass were due to large catches in only a few hauls.
The aggregated nature of the distribution of this
school-forming squid was also observed in acoustic
surveys by Madureira et al. (2005), who estimated
total biomasses of I. argentinus as high as 31,742 ton
in April and May 1997.
As are all species of the genera, I. argentinus is a
fast-growing, short-lived species with highly variable
interannual abundance (Rodhouse et al., 1998); for a
review, see Perez et al. (2009). Recorded commercial
landings in 2002 reached 2,601 ton, far higher than in
the previous and following years (Fig. 3). It is very
likely that the high proportion of I. argentinus in the
catch of the autumn 2002 survey corresponded to an
exceptionally high recruitment.
Urophycis mystacea
The size distribution of commercial landings of the
gulf-hake Urophycis mystacea in southern Brazil included fishes over 100 g and 250 mm TL (Haimovici
et al., 2006b). In the surveys, 98% (in weight) of the
gulf-hake caught exceeded this size (Table 5). This
species does not seem to form dense schools; rather, it
was caught in a large number of hauls but without
outstanding individual catches. For this reason, biomass estimates were relatively precise compared with
those of other species: 8,583 ton (± 24%) in winterspring and 11,204 ton (± 41%) in summer-autumn
(Table 3). Larger catches occurred in the southern area
in both seasons at depths over 150 m and further north
at depths over 300 m (Fig. 2).
Urophycis mystacea is a relatively slow-growing
species that lives at least 14 years and reaches sexual
maturity between three and six years (Martins & Haimovici, 2000; Haimovici et al., 2006b). This species
was part of the bycatch of the bottom longline fishery
that has targeted the wreckfish Polyprion americanus
since the 1970s (Haimovici et al., 2003). Landings
statistics of Urophycis brasiliensis and U. mystacea
were not differentiated in most states. Pooled landings
of both species were a little above 2,000 ton from
1996 to 2000, increased sharply to 6,013 ton and
8,192 ton in 2002, and decreased slowly in the follo-
402
Table 5. Biomass estimates of the commercial size fraction of the important species in the REVIZEE bottom trawl surveys on the outer shelf and upper slope in southern Brazil (2001-2002) in winter-spring (w-s) and summer-autumn (s-a).
The 90% confidence intervals are shown as percentage of the estimated biomasses
Tabla 5. Biomasas estimadas de las especies y tamaños de interés comercial en los levantamientos de arrastre de fondo
del programa REVIZEE realizados en la plataforma externa y talud superior del sur y sudeste de Brasil (2001-2002) en
invierno-primavera (w-s) y verano-otoño (s-a). El intervalo de 90% de confianza está expresado como porcentaje de la
biomasa.
Depth ranges
Shelf
100-199 m
Upper slope
200-600 m
Areas
92,555 km2
2
Total commercial biomass
Illex argentinus
Merluccius hubbsi
Zenopsis conchifera
Urophycis mystacea
Polymixia lowei
42,168 km
Total area
100-600 m
2
134,724 km
± IC 90%
biomass
w-s
92,398
74,795
167,193
22%
s-a
69,167
96,292
165,460
25%
w-s
5
8,907
8,912
106%
s-a
0
28,647
28,647
62%
w-s
3,079
11,376
14,455
43%
s-a
3,111
12,968
16,078
32%
w-s
6,456
21,760
28,216
61%
s-a
242
20,760
21,003
87%
w-s
3,049
5,535
8,583
24%
s-a
5,453
5,751
11,204
41%
w-s
0
14,854
14,854
85%
s-a
15
17,713
17,728
69%
w-s
9,993
6,002
15,994
27%
s-a
5,213
5,758
10,971
23%
Table 6. Mean densities (kg km-2) of pooled commercially important species in the REVIZEE bottom trawl surveys on
the outer shelf and upper slope in southern Brazil (2001-2002).
Tabla 6. Densidades medias (kg km-2) de las especies de importancia comercial en los muestreos pesqueros de arrastre de
fondo del Programa REVIZEE realizados en la plataforma externa y talud superior del sur de Brasil (2001-2002).
Latitudinal strata
All latitudinal
Latitudinal strata
C and D
strata
A and B
100-199 m 200-600 m 100-200 m 200-600 m 100-200 m 200-600 m
Area (km2)
Winter-Spring surveys
(2001-2002)
Summer-Autumn surveys
(2002)
Total
31,952
38,719
37,655
44,029
69,607
82,749
152,355
2,143
1,059
0,636
0,767
0,829
0,904
0,904
1,485
1,642
0,577
0,743
0,782
1,164
1,164
wing years (Fig. 3). If we assume that landings of U.
brasiliensis remained stable at 2,000 ton, those of U.
mystacea peaked at approximately 6,000 ton in 2002
and decreased in the following years.
Merluccius hubbsi
Commercial landings of the Argentine hake Merluccius hubbsi in southern Brazil considered fish over
100 g and 250 mm (Haimovici et al., 1993). In the
403
Figure 2. Estimated biomass of marketable species (tons) on the outer shelf and upper slope in the bottom trawl
REVIZEE surveys in southern Brazil (2001-2002) (A-D are latitudinal strata defined in the text).
Figura 2. Biomasa estimada de especies de valor comercial (ton), en los levantamientos de arrastre de fondo del programa REVIZEE en el sur de Brasil realizados en la plataforma externa y talud superior (2001-2002). (A-D estratos latitudinales definidos en el texto).
Figure 3. Annual landings (tons) of the main species in
bottom trawl and bottom gillnet catches on upper-slope
of southern Brazil (Valentini & Pezzuto, 2006; IBAMA,
2007).
Figura 3. Desembarques anuales (ton) de las principales
especies demersales del talud superior de la flota de
arrastreros de fondo y de enmalle de fondo de la pesca en
el sur de Brasil (Valentini & Pezzuto, 2006; IBAMA,
2007).
surveys, 85% (in weight) of the species caught were
over this size. Biomass estimates were 14,445 ton (±
43%) in winter-spring and 16,078 ton (± 32%) in summer-autumn, with nearly 3/4 caught on the upper slope
(Table 5). The largest concentrations of this species
were found in the southern and northern parts of the
study area at depths over 300 m (Fig. 4). However,
smaller than commercial-sized specimens were far
more abundant numerically and occurred in catches at
all latitudes and in all depth ranges, particularly on the
outer shelf (Haimovici et al., 2008).
Annual landings of Argentine hake were below
300 ton until 2001; these were fished mostly off Rio
de Janeiro and in Rio Grande do Sul in the years with
a strong influence of cold waters from the Malvinas
Current (Haimovici, 1997). Landings increased
sharply in 2001 to 2,654 ton, peaked at 4,479 in 2002,
and decreased to 1,565 by 2005 (Fig. 3).
Polymixia lowei
Commercial landings of the beardfish Polymixia lowei
are rare and no information is available on its marketing. Occasionally, trawlers fishing on the upper slope
404
Figure 4. Densities (kg km-2) of the commercial size catches of Illex argentinus, Urophycis mystacea, Merluccius hubbsi,
Polymixia lowei, Zenopsis conchifera and Lophius gastrophysus captured in winter-spring (left) and summer-autumn
(right) REVIZEE surveys (2001-2002) by depth and latitude in southern Brazil. For each species and survey, the diameters of the largest circles represent the largest densities.
Figura 4. Densidades (kg km-2) de ejemplares de tamaño comercial de Illex argentinus, Urophycis mystacea, Merluccius
hubbsi, Polymixia lowei, Zenopsis conchifera y Lophius gastrophysus capturados en invierno-primavera (izquierda) y
verano-otoño (derecha) por profundidades y latitudes en los muestreos pesqueros del programa REVIZEE en el sur de
Brasil (2001-2002). Para cada especie los diámetros de los círculos representan las mayores densidades.
obtain large catches of specimens over 100 g and 200
mm total length; these specimens bring low prices
when landed because, according to the fishermen, they
have too many spines. In the surveys, 91% (in weight)
of the P. lowei caught were over this size and the potential commercial biomass estimates were 14,827 ton
(± 63%) in winter-spring and 17,721 ton (± 85 %) in
summer-autumn (Table 5). Wide confidence intervals
occurred due to large catches in a few hauls; this species was very abundant in a few hauls at depths over
300 m between 23ºS and 26ºS (Fig. 4). Specimens
smaller than the commercial size were more frequent
to the south of Cabo de Santa Marta Grande in the 150
to 300 m depth range and at all latitudes between 300
and 400 m (Haimovici et al., 2008). The maximum
total length of this species is under 300 mm and its
biology is poorly known.
Zenopsis conchifera
The silvery John dory Zenopsis conchifera is a benthopelagic species with low commercial value that is
caught incidentally by large foreign trawlers on the
upper slope (Perez et al., 2003). Due to its laterally
compressed body and large dermal bones along the
body, only large specimens are adequate for filleting.
Thus, only samples in which the mean weight of the
fishes was over 350 g were considered for biomass
estimates with commercial value. In the surveys, 67%
(in weight) of the Z. conchifera caught were over this
size and biomass estimates were 28,216 ton (± 61%)
in winter-spring and 21,003 ton (± 87%) in summerautumn (Table 5). As large catches occurred in only a
few hauls, the estimated confidence intervals of the
biomass were large. Higher densities of commercialsized Z. conchifera were found at 300 to 400 m depth
in all seasons in Cabo de Santa Marta Grande region
and also along Ilha Bela in summer-autumn (Fig. 4).
Specimens smaller than the commercial size occurred
mostly over the shelf break (Haimovici et al., 2008).
The monkfish Lophius gastrophysus was the fish with
the highest commercial value among the frequently
caught species. This fish has a very large head and
specimens under 350 g are not considered to be of
commercial interest and are not usually landed
(Schwingel & Andrade, 2002). As few of the L. gastrophysus caught were smaller than this size, all their
catches were considered to have commercial value.
The winter-spring biomass was estimated to be 15,994
ton (± 27%), with 9,993 ton caught on the outer shelf
and 6,002 ton on the upper slope; the summer-autumn
biomass was 10,971 ton (± 23%), of which 47.5%
were caught on the outer shelf (Table 5). The monkfish was caught along all the study area in both surveys. Larger densities were found in both surveys
between Conceição and (area B) and also between
Cabo de Santa Marta Grande and Cabo Frio (areas C
and D) in summer-autumn (Fig. 4). The smallest
specimens, of low commercial value, occurred mostly
on the outer shelf and shelf break and the largest ones
on the upper slope at depths between 250 and 550 m
(Haimovici et al., 2008).
The monkfish was exploited on the outer shelf of
Rio de Janeiro by the local industrial fishing fleet for
decades. Landings increased sharply due to the foreign
gillnet fleet that operated from 1999 to 2002 all along
the upper slope of southern Brazil (Perez et al., 2002;
2005). Total landings peaked at 7,094 ton in 2001 and
5,129 ton in 2002 and decreased to around 2,500 ton
in the later years (Fig. 3).
Fishing potential estimates
Gulland’s formula was used for the first appraisal of
the potential yield of the demersal fish resources vulnerable to bottom trawls on the outer shelf and upper
405
slope of southern Brazil. This approach is not adequate for short-lived species with highly variable recruitment and abundance such as Illex argentinus.
Therefore, the values of this species were not included
in the analysis.
The biomasses estimated from the surveys cannot
be considered to be unexploited stocks (Bo) since the
outer shelf has been fished for years and landings of
Argentine hake, gulf-hake, and monkfish, which were
low until 2000, increased to around 13,500 ton in 2001
and 15,800 in 2002 (Fig. 3). Furthermore, the gulfhake has been caught as bycatch of the bottom
longline fishery since the 1970s (Peres & Haimovici,
1998; Haimovici et al., 2004). Similarly, elasmobranches have been caught on the outer shelf by diverse gears since the 1980s (Vooren & Klippel, 2005).
Thus, our best choice for the exploitable biomass
(exBo) was the biomass estimate of commercially
valuable fishes in the 2001 winter-spring survey, excluding I. argentinus (149,369 ton) and including the
recorded catches of the most important species in
2001 (13,500 ton), for a total of around 165,000 ton.
The potential yield of commercially valuable species was: Y = 0.4 · 0.31 · 165,000 ton = 20,460 ton.
However, 12.4% of the total commercial size of marketable fish biomass were elasmobranches (Squatina
spp. and other legally protected species), which have
slow growth rates and low reproductive potential. Two
potentially marketable species, Polymixia lowei and
Zenopsis conchifera, which represented 18.3%, are
presently discarded or have very little value. Thus,
only three of the species (Argentine hake, gulf-hake,
monkfish) are, at present, targeted by commercial
fishing on the upper slope and their potential yield
may provide a more realistic estimate of the fishing
potential of the demersal fishes vulnerable to trawls in
this environment. Their pooled biomass in the winterspring survey was 39,033 ton. When added to the
13,500 ton of these species caught in 2001, the total
was 53,433 ton. Their common natural mortality was
also estimated at 0.31 and their potential yield was: Y
= 0.4 · 0.31 · 53,433 ton = 6,626.
DISCUSSION
The overall picture revealed by the surveys is that the
demersal fish densities and fishery potential of the
outer shelf and upper slope of southern Brazil is lower
than that of the inner shelf and the same depth ranges
farther south off Uruguay and Argentina but higher
than in central and northeastern Brazil (MMA, 2006).
This result is not unexpected since it agrees with the
differences in productivity of the corresponding environments (Castello & Odebrecht, 2001). The influence
406
of the nearby richer waters to the south is corroborated
by the higher densities in the southern half of the
study area. This pattern was also observed for fishes
vulnerable to bottom longlines (Haimovici et al.,
2004). However, the lower biomass and densities of
commercially valuable fishes on the outer shelf (as
compared to the upper slope; Fig. 3) may have another
explanation: very intense fishing on the shelf over the
last forty years could have reduced the abundance of
species occurring on both the inner and outer shelf
such as sciaenids, red porgy, flatfishes, and elasmobranches (Haimovici, 1997; Haimovici et al., 2006c).
Commercially valuable species have also been fished
on the upper slope but for a far shorter period of time.
The pooled recorded catch of Argentine hake, gulfhake, and monkfish was 13,761 ton in 2001, 15,800
ton in 2002, and 9,413 ton in 2003. These values were
respectively 107%, 138%, and 42% above the common potential yield, estimated to be 6,625 ton. This
may have reduced their exploitable biomass substantially. In fact, reported landings of Argentine hake,
gulf-hake, and monkfish in later years decreased to a
fraction of those from 2001-2002. In part, this decrease coincided with the exit of most of the foreign
fishing vessels in the former years (Perez et al., 2009).
The estimates of the potential yield presented in
this paper were subject to a considerable bias. Underestimates of the swept area due to both gear and fish
behavior may have led to underestimates of the standing biomass. Additionally, incomplete landing reports
affected the proposed correction factor. Considering
that all three species were already exploited before the
surveys and based on life story parameters, Perez
(2006) concluded that sustainable yields for Argentine
hake, gulf-hake, and monkfish should not be over 10%
of the virginal exploitable biomass. His estimate does
not differ substantially from our results based on bottom trawl survey biomass estimates.
Presently, over 700 industrial fishing boats are operating along southern Brazil (unpublished data, Fisheries and Aquaculture Ministry), including trawlers
and gill-net fishing boats. Despite being smaller than
the foreign fishing boats and having poor fishing and
processing technology, many of these could fish on
the upper slope. However, the cost-benefit relationship
does not appear to be attractive to most of them. For
this reason, we believe that the abundance of these
species and their fishing potential is likely to be far
lower than expected in previous years and unlikely to
have been as high as expected or higher than that reported in this paper.
Theoretically, the fourth important fishing resource, Illex argentinus, with an estimated biomass of
over 26,000 ton in the summer-autumn 2002 survey,
could yield over 10,000 ton if an escape of 40% was
allowed, as recommended in the literature (Beddington, 1990). However, this yield would demand a very
high fishing effort in a very short fishing season,
which is not economically feasible. In fact, landings of
the short-fin Argentine squid only reached 2,500 ton
in 2002 and were far lower in the previous and following years (Fig. 3). If managed, I. argentinus could be
fished opportunistically, with high yields in some
years and none in most of the others.
The surveys did not reveal substantial new fishing
resources vulnerable to bottom trawls between 100
and 600 m depth and showed limited potential of those
already exploited; in fact, this potential was substantially lower than that on the inner shelf. Therefore, this
environment cannot be considered to be a “new frontier” for the expansion of fishing, and exploitation
must be carefully controlled to avoid overfishing.
ACKNOWLEDGEMENTS
We acknowledge onboard assistance of the R/V
Atlântico Sul and R/V Soloncy Moura crews and
colleagues at the Federal University of Rio Grande
(FURG) and São Paulo (USP) and the Fisheries
Institute of São Paulo State. We also thank two
anonymous reviewers for their helpful comments.
Logistical support for the research vessels was
provided by CEPSUL/IBAMA and FURG. This
research was based on surveys funded by the
REVIZEE Program. The first author was partly
supported by grants from the Brazilian Research
Council (CNPq). CNPq and the REVIZEE Program
provided grants for R.A.B., L.G.B., and R.A.S.
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Population biology of Illex argentinus off Brazil
Research Article
Biological patterns of the Argentine shortfin squid Illex argentinus
in the slope trawl fishery off Brazil
José Angel Alvarez Perez1, Tiago Nascimento Silva2, Rafael Schroeder1,3
Richard Schwarz1,3 & Rodrigo Silvestre Martins4,5
1
Grupo de Estudos Pesqueiros. Centro de Ciências Tecnológicas da Terra e do Mar.
Universidade do Vale do Itajaí, Rua Uruguai 458, Centro, Itajaí, SC, Brazil
2
Biogás Energia Ambiental S.A., Rua Mogeiro 1580. Bairro Perus, 05206-240 São Paulo, SP, Brazil
3
Curso de Pós-Graduação em Ciência e Tecnologia Ambiental, Centro de Ciências Tecnológicas
da Terra e do Mar, Universidade do Vale do Itajaí, Rua Uruguai 458, Centro, Itajaí, SC, Brazil
4
Marine and Coastal Management (MCM), Private Bag X2, Rogge Bay 8012, Cape Town, South Africa
5
Zoology Department and Marine Research Centre, University of Cape Town, Private Bag X3,
Rondebosch 7701, Cape Town, South Africa
ABSTRACT. Commercial exploitation of the Argentine shortfin squid (Illex argentinus) was virtually nonexistent in Brazilian waters until 2000 when foreign trawlers initiated their operations on slope grounds as part
of a government-induced chartering program. Since then, the species has been included among the targets of a
developing slope trawl fishing off southeastern and southern Brazil. Biological samples were collected from
commercial catches of 25 national and seven foreign (chartered) trawlers between 23°-33°S and 170-740 m
depth. These samples represent two periods of the commercial exploitation of Illex argentinus in Brazil: 20012003, when both chartered and national trawlers operated simultaneously, and 2006-2007, when only national
vessels continued to exploit I. argentinus along with other slope stocks. Catches contained immature and maturing squid throughout the year, as well as at least two distinct, fully mature, spawning groups: one composed
of small-sized males and females present year-round on the shelf-break/ upper slope (< 400 m), and the other
consisting of large squid present only in austral winter-spring in southern (26°-29°S) and deep fishing grounds
(400-700 m). The latter group has sustained the large winter catches reported since 2000 and the large sizes
and concentrations of the specimens sparked the interest of the fishing industry as a potential target of the
slope fishery. The reproductive attributes and temporal/ spatial distribution patterns of winter spawners support the hypothesis that relates this group to migrating concentrations of a north Patagonian shelf stock. If confirmed, the present data would underscore the need to consider multinational shared stock management strategies in the SW Atlantic.
Keywords: ommastrephid squid, Illex argentinus, slope trawl fishery, southern Brazil.
Patrones biológicos del calamar argentino Illex argentinus en la pesquería de
arrastre en el talud continental de Brasil
RESUMEN. La explotación comercial del calamar argentino (Illex argentinus) no existía en aguas brasileñas hasta el año 2000, cuando buques extranjeros iniciaron sus operaciones en el talud como parte de
un programa gubernamental de arrendamiento. Desde entonces la especie forma parte de un conjunto de
recursos que han motivado el desarrollo de una pesquería de arrastre en el talud del sur y sureste de Brasil. Se colectaron muestras biológicas de las capturas comerciales de 25 buques arrastreros nacionales y
siete extranjeros entre los paralelos 23°-33°S y en profundidades de 170 a 740 m. Estas muestras representaron dos periodos de la explotación comercial de I. argentinus en Brasil: 2001-2003, cuando buques
nacionales y extranjeros operaron simultáneamente, y 2006-2007 cuando sólo buques nacionales permanecieron explotando el calamar argentino en conjunto con otros recursos del talud. Las capturas estuvie-
409
410
ron constituidas por calamares inmaduros y en-maduración a lo largo de todo el año, así como al menos
dos grupos distintos de individuos maduros y desovantes: un grupo constituido por machos y hembras de
pequeño tamaño que están presentes en todas las estaciones del año en el borde de la plataforma continental y talud superior (< 400 m), y otro grupo, constituido por calamares de gran tamaño, presente solamente durante el invierno-primavera australes en áreas sureñas (26°-29°S) y profundidad (400-700 m).
Este grupo ha sostenido las grandes capturas invernales reportadas desde 2000 y, dado su largo tamaño y
concentración, ha justificado el interés de la industria pesquera como un potencial recurso para la pesca
en el talud. Características reproductivas y patrones de distribución temporales/ espaciales de los desovantes de invierno corroboran la hipótesis que les relaciona a concentraciones migratorias de stock del
norte de la plataforma Patagónica. Si se confirma esta hipótesis, estos datos resaltan la importancia de
considerar estrategias de manejo dirigidas a stocks compartidos en el Atlántico SW.
Palabras clave: calamares omastréfidos, Illex argentinus, pesquería de arrastre de talud, sur de Brasil.
________________________
Corresponding author: José Angel Alvarez Perez ([email protected])
INTRODUCTION
Squids have long represented important bycatch components of the multispecific trawl fishery off Brazil
(Costa & Haimovici, 1990; Perez & Pezzuto, 1998).
On the continental shelf, loliginids have further become seasonal targets of both hand jigging and trawl
fisheries, as they are densely concentrated in space
and time (Perez, 2000; Martins & Perez, 2007). In
recent years, however, commercial landings of the
ommastrephid Argentine shortfin squid Illex argentinus (Castellanos, 1960) have been recorded in the
southeastern and southern sectors of the Brazilian
coast and have placed this squid among the main
cephalopod resources exploited in the country (Perez
et al., 2009a).
The species is distributed in the SW Atlantic from
Rio de Janeiro (23°S) to southern Argentina (54°S)
sustaining, on the Patagonian shelf and around the
Falkland (Malvinas) Islands, one of the largest cephalopod fisheries in the world (Boyle & Rodhouse,
2005). Off Brazil, several fishing surveys conducted
since the 1970s have revealed important concentrations of paralarvae, juveniles, and spawning individuals, particularly in the shelf break and slope waters of
the southern coast (south of 25°S) (Haimovici & Andriguetto Fo, 1986; Haimovici & Perez, 1991; Haimovici et al., 1995, 2007, 2008). In this area, the species has also been often found in stomach contents of
large predators, and it is regarded as one of the key
components of both pelagic and demersal trophic
chains (Santos & Haimovici, 2000; Gasalla et al.,
2007).
Commercial exploitation of the Argentine shortfin
squid was virtually non-existent in Brazilian waters
until 2000, when foreign-chartered trawlers initiated
their operations on the slope grounds south of 20°S
(Perez et al., 2003, 2009b). In that year, the Portuguese trawler “Joana” landed approximately 48 ton of
this species caught during one fishing trip between 2629°S and 235-401 m isobaths (Perez et al., 2003). In
2002, the South-Korean trawler “In Sung 207” exploited the same area in winter (June-September)
catching, on average, 199 kg of I. argentinus per
trawling hour. After four fishing trips, this vessel
landed a total of 1,400 ton, the largest catch ever recorded in Brazilian waters (Perez et al., 2009b). In
total, landings of I. argentinus that year reached 2,601
ton, nearly twice the amount recorded for other squids
(mostly loliginids). These catches, however, decreased
to 100-400 ton in the following years, as chartered
trawlers either abandoned Brazilian waters or moved
to deeper areas (> 700 m). Since then, national trawlers have included I. argentinus among the targets of a
developing “upper slope” (250-500 m) trawl fishery
(Perez & Pezzuto, 2006; Perez et al., 2009a).
Preliminary assessments of this fishery have considered I. argentinus to be a seasonal resource with a
fishing potential that has not been objectively defined
but that is generally considered to be highly variable
and unpredictable (Haimovici et al., 2006). The main
questions regarding the biological aspects of I. argentinus commercial exploitation off Brazil, however,
revolve around its complex population structure and
potential connections with migrating stocks exploited
off Uruguay and Argentina (Perez et al., 2003; Haimovici et al., 2006). As most ommastrephid squids, I.
argentinus is a short-lived species (~1 year) that matures late in life and dies after a single and terminal
spawning event (Haimovici et al., 1998). Because
generations do not overlap in time, population resilience is highly dependent on recruitment and, consequently, annual abundances typically exhibit wide
oscillations, as do commercial catches (Boyle & Rod-
411
house, 2005). Associated with this extreme life history
pattern, ommastrephids tend to combine extended
spawning seasons, long reproductive migrations, and
the passive transport of offspring by surface geostrophic currents to produce both seasonal and geographic
population units (stocks); this complex structure is
regarded as an evolutionary strategy to minimize the
risks of semelparity (O’Dor, 1998).
In the SW Atlantic, at least four stocks were distinguished from general size-at-maturity patterns:
summer spawning stock (SSS), south Patagonian stock
(SPS), Bonaerensis north Patagonian stock (BNS), and
southern Brazil stock (SBS) (Brunetti, 1988; Haimovici et al., 1998). The latter group included the
main concentrations of spawning squid found in winter months on the slope off southern Brazil (Haimovici
& Perez, 1990; Santos & Haimovici, 1997). Growing
biological evidence (i.e. maturation patterns, trophic
relationships, the occurrence of certain parasites, statolith morphometrics), however, suggests that these
squid are in fact BNS members that migrate north to
spawn in Brazilian waters (Santos & Haimovici, 1997;
Schwarz & Perez, 2007). Although local spawning
was also observed occuring off Brazil throughout the
year, winter spawning was potentially linked to recruitment off the northern Patagonian shelf through
paralarval transport by the Falkland (Malvinas) – Brazil Current system (Haimovici et al., 1995). In this
context, this study analyzes biological attributes of
commercial catches of the Argentine shortfin squid off
southern Brazil as a descriptive approach to assess
both the population structure subject to the seasonal
exploitation regime and the hypothesis of a shared
stock scenario.
Biological samples of the Argentine shortfin squid
were obtained from commercial catches of 25 national
and seven foreign (chartered) trawlers all derived from
operations in the southeastern and southern sectors of
the Brazilian coast (Fig. 1) between 23°-33°S and 170740 m depth. Samples represent two periods of the
species’ commercial exploitation in Brazil: 20012003, when both chartered and national slope trawlers
operated simultaneously, and 2006-2007, when only
national vessels continued to exploit I. argentinus
along with other slope stocks (Table 1) (Perez &
Pezzuto, 2006; Perez et al., 2009b).
Onboard observers collected samples from chartered trawlers for all fishing trips conducted principally between September 2001 and April 2003. After
each positive trawl, a sample was taken from the catch
Figure 1. Spatial distribution of Argentine shortfin squid
Illex argentinus catches off southeastern and southern
Brazil. a) chartered trawlers (2001-2003), b) national
trawlers (2006-2007). Latitude and longitude were decimal transformed.
Figura 1. Distribución espacial de las capturas del calamar argentino Illex argentinus en el sureste y sur de
Brasil. a) arrastreros arrendados (2001-2003), b) arrastreros nacionales (2006-2007). Latitudes y longitudes
fueron transformadas en valores decimales.
and deep-frozen for posterior analysis in the laboratory ashore. Each sample had detailed information on
trawl position (lat-long), date, time, and fishing effort
(trawling hours). Samples from national trawlers were
collected from landings at the harbors of Santa Ca-
412
Table 1. Summary of data for the Argentine shortfin squid Illex argentinus obtained from chartered and national trawlers
operating off Brazil between 2001 and 2007. N: number of individuals; Min-Max: smallest and largest mantle length
(ML) and total wet body weight (BW).
Tabla 1. Resumen de datos de calamar argentino Illex argentinus obtenidos en las operaciones de pesca de arrastreros
arrendados y nacionales en Brasil entre 2001 y 2007. N: número de individuos, Min-Max: valores máximos y mínimos de
la longitud del manto (ML) y peso total húmedo (BW).
Males
Trimester
N
Females
ML (mm)
Min-Max
BW (g)
Min – Max
ML (mm)
Min – Max
BW (g)
Min – Max
14 – 240
23 – 425
25 – 295
26 – 345
27 – 570
260 – 420
29 – 188
40 – 192
195 – 325
24
506
262
524
307
7
60
130
1
91 – 332
105 – 336
98 – 254
104 – 299
114 – 346
280 – 325
143 – 234
130 – 250
250
18 – 455
33 – 655
18 – 320
23 – 560
26 – 775
228 – 670
52 – 260
43 – 400
162
N
Chartered
Jan-Mar/2001
Apr-Jun/2001
Jul-Sep/2001
Oct-Dec/2001
Jan-Mar/2002
Apr-Jun/2002
Jul-Sep/2002
Oct-Dec/2002
Jan-Mar/2003
Apr-Jun/2003
Apr-Jun/2006
Jul-Sep/2006
32
966
395
466
153
4
73
131
7
78 – 195
110 – 278
115 – 221
115 – 239
119 – 316
221 – 275
105 – 191
123 – 200
229 – 259
Total
2227
78 – 316
14 – 570
1821
91 – 346
18 – 775
Jan-Mar/2001
Apr-Jun/2001
Jul-Sep/2001
Oct-Dec/2001
Jan-Mar/2002
Apr-Jun/2002
Jul-Sep/2002
Oct-Dec/2002
Jan-Mar/2003
Apr-Jun/2003
Apr-Jun/2006
Jul-Sep/2006
Oct-Dec/2006
Jan-Mar/2007
Apr-Jun/2007
Jul-Sep/2007
Oct-Dec/2007
Total
4
136
12
36
81
86
95
5
76 – 121
30 – 253
163 – 405
38 – 148
30 – 309
30 – 335
31 – 450
211 – 249
100 – 315
49 – 162
128 – 470
28 – 390
6
213
16
89
125
88
86
8
27
24
43
73
154 – 174
129 – 245
190 – 261
135 – 166
114 – 254
100 – 250
110 – 340
220 – 262
159 – 225
130 – 210
110 – 289
111 – 249
16
51
45
77
155 – 185
115 – 395
195 – 315
124 – 204
117 – 262
130 – 376
118 – 350
252 – 367
190 – 290
117 – 305
166 – 351
132 – 344
79 – 145
32 – 580
90 – 655
39 – 255
31 – 375
44 – 605
25 – 830
196 – 580
180 – 645
68 – 700
57 – 860
35 - 870
75
46
145 -246
160 - 289
50 -299
116 - 505
122
54
135 - 338
223 - 353
37 -740
184 -910
743
100 – 340
28 - 505
996
115 - 395
25 - 910
TOTAL
2970
78 – 340
14 - 570
2817
91 - 395
18 - 910
National
413
tarina state (southern Brazil) as part of a daily fishery
sampling program (Perez et al., 1998). From each
landed catch, approximately 20 kg of squid were
measured for their dorsal mantle length (ML) to the
nearest centimeter, and a length stratified subsample
was taken to the laboratory. These subsamples could
not be related to individual trawls conducted during
each fishing trip, but represented the entire fishing
area covered by it. Information on the fishing area,
effort (mean trawl duration, number of trawls per day,
trip duration in days), and total catch were obtained
during interviews with skippers at the time of the landings.
In the laboratory, the ML and the total body weight
(BW) were recorded to the nearest millimeter and
gram, respectively. After dissecting the mantle, males
and females were differentiated and maturity stages
were assigned according to the macroscopic scale
proposed by Brunetti (1990). This scale defined seven
and eight maturity stages for males and females, respectively, including: immature (stages I and II), in
maturation (stage III), early maturity (stage IV), advanced maturity (stage V), spawning (stage VI for
males and stages VI and VII for females), and spent
(stage VII for males and stage VIII for females).
In females, the ovary and accessory organs (oviduct + nidamental glands + oviducal gland) were
weighed (OW and AOW, respectively), the nidamental gland length was measured (NGL), and the gills
were checked for the presence of spermatophores as
signs of mating. In males, the testis and accessory
organs (spermatophoric complex + Needhan’s sac +
penis) were weighed (TW and AOW, respectively),
the testis length was measured (TL), and the
Needhans’s sac was examined for the presence of
spermatophores. All weights were taken to the nearest
0.1 g and measurements to 0.1 mm.
c) the Testis (TI) - Nidamental Gland (NGI) indices
defined as
TI =
TL
,
ML
NGI =
NGL
ML
(3)
A data bank was produced in which each squid was
described by its origin (sample, landing date), sex, size
(ML, BW), and reproductive characteristics (maturity
stage, OW, TW, AOW, GSI, HI, TI/ NGI).
Size-at-maturity was assessed from the cumulative
ML frequency distribution of mature and spawning
males and females (stages > IV). This distribution was
linearized by the probit transformation of cumulative
ML frequencies and a straight line was then fitted to
the transformed frequency vs. ML class relationship
using the least-squares method. Precise ML at different percentiles were then estimated by substituting the
probit values in the estimated linear equation (i.e.
probit 5 corresponds to 50% percentile):
MLm =
pf − c
d
(4)
Maturation in males and females was expressed
numerically by three indices:
where pf is the probit transformed ML cumulative
frequency and c and d are the intercept and the slope
of the fitted line, respectively.
Population differentiation among squid caught by
commercial trawlers was explored through a multivariate Principal Component Analysis (PCA) applied
separately for males and females. Variables included
in this analysis involved size and reproductive attributes (BW, GSI, HI, TI/ NGI), day-of-the-year (DYR),
decimal latitude (LAT), decimal longitude (LONG),
and depth (DEPTH). A correlation matrix was calculated for the variables (previously standardized as a
proportion of their mean) and new axes (factors) were
extracted in the direction of greatest variance. These
factors were linear combinations of the original variables and used to interpret the potential existence of
biologically similar groups of squids and their occurrence in space and time.
a) the Gonadosomatic index defined for males
(GSIM) and females (GSIF) as:
RESULTS
GSI M =
GSI F =
TW + AOW
100
(BW − (TW + AOW ))
OW + AOW
(BW − (OW + AOW ))
(1)
100
b) the Hayashi index (HI) defined for males (HIM)
and females (HIF) as
HI M =
AOW
TW + AOW
,
HI F =
AOW
OW + AOW
(2)
Size structure of catches
Males and females caught during slope trawl fishing
exhibited a bi-modal ML frequency distribution (Fig.
2). Males ranged from 78 to 340 mm ML, exhibiting
one pronounced mode centered around 160 mm ML
and a secondary mode between 220 and 240 mm ML.
Females were generally larger, ranging from 91 to 395
mm ML. A main modal group was formed around 180
mm ML and a less pronounced one between 280-320
414
mm ML (Fig. 2, Table 1). The overall size structures
remained practically unchanged as the catches by the
chartered and national trawlers in 2001-2007 were
examined separately, although larger females were
found in the former (Fig. 2).
During the early exploitation period (2001-2003),
the size structure of the chartered fleet catches varied
with the season, latitude, and depth of commercial
operations (Figs. 3 and 4). Large males (ML > 200
mm) dominated catches obtained in winter (JulySeptember) south of 28°S, between 350-540 m depth
(Fig. 3). During the rest of the year, catches were generally unimodal, concentrating on individuals between
100-250 mm ML that originated north of 28°S and on
the upper slope (< 400 m depth). In females, the patterns observed were virtually the same (Fig. 4), with
an uniform group of individuals (100-250 mm ML
long) dominating the catches throughout the year,
except for winter months when a distinct group of
large females was caught in southern (south of 28°S)
and deeper (> 350 m) areas.
Slope trawling between 2006-2007, as conducted
by the national fleet, concentrated on the larger fractions of both males and females (Fig. 5). These fractions were generally obtained in areas south of 29°S
(Fig. 1), inshore of the 400 m isobath, and in autumn
(April-June) and winter (July-September) months.
Maturation and maturity stages
Males and females in all maturity stages were present
in the slope trawling catches off southeastern and
southern Brazil (Table 2). The spawning stage (stage
VI) was the most frequently identified maturity condition in both sexes and nearly 50% off all individuals
caught were at least in an early maturity stage (stage
IV and higher). This overall maturity stage composition was observed in 2001-2003 but shifted towards a
complete dominance of spawning (and spent) squid
after 2003, as the national trawlers that continued to
exploit the Argentine shortfin squid tended to catch
and land larger males and females (Fig. 6).
Catches included immature males and females as
small as 78 and 91 mm ML, respectively. Spawning
males (stage VI) and females (stage VII) attained the
largest sizes (Table 2). Squids of both sexes enlarged
homogenously as maturation progressed. At an advanced maturity-spawning condition (stages V, VI,
and VII), however, two distinct size groups were
found (Fig. 7). The first group was dominant in the
samples and was composed of males and females
ranging from 140-180 mm ML and 160-240 mm ML,
respectively. The second group was less abundant but
included larger individuals (males > 200 mm ML;
Figure 2. Mantle length frequency distributions (in mm)
of males and females of the Argentine shortfin squid Illex
argentinus caught by commercial trawlers off Brazilian
coast between 2001 and 2007. a) total catches, b) male
catches obtained by chartered vs. national trawlers, c)
female catches obtained by chartered vs. national trawlers.
Figura 2. Distribución de tallas (largo de manto ML en
mm) de machos y hembras del calamar argentino Illex
argentinus capturados por arrastreros comerciales en la
costa de Brasil entre 2001 y 2007. a) capturas totales, b)
capturas de machos obtenidas por arrastreros arrendados
y nacionales, c) capturas de hembras obtenidas por arrastreros arrendados y nacionales.
415
Figure 3. Size structure of male Illex argentinus caught by chartered trawlers off Brazil between 2001 and 2003. Mantle
length frequency distributions (in mm) are presented by latitudinal (left column) and depth (right column) strata. Colors
differentiate maturity stages according to the Brunetti (1990) macroscopic scale.
Figura 3. Estructura de tallas de machos del calamar argentino Illex argentinus capturados por arrastreros arrendados en
Brasil entre 2001 y 2003. Las distribuciones de frecuencia de tallas (largo de manto ML en mm) están presentadas por
estratos latitudinales (columna de la izquierda) y estratos batimétricos (columna de la derecha). Los colores diferencian
los estadios de maduración sexual según la escala macroscópica de Brunetti (1990).
416
Jan - Mar
Jan - Mar
Stages
I+II
IV+V
VI+VII+VIII
I+II
IV+V
VI+VII+VIII
Apr - Jun
Apr - Jun
Stages
Stages
I+II
IV+V
VI+VII+VIII
I+II
IV+V
VI+VII+VIII
Jul - Sep
Jul - Sep
Stages
Stages
Stages
I+II
IV+V
VI+VII+VIII
I+II
IV+V
VI+VII+VIII
Oct - Dec
Oct - Dec
Stages
I+II
IV+V
VI+VII+VIII
Stages
I+II
IV+V
VI+VII+VIII
Figure 4. Size structure of female Illex argentinus caught by chartered trawlers off Brazil between 2001 and 2003. Mantle
length frequency distributions (in mm) are presented by latitudinal (left column) and depth (right column) strata. Colors
differentiate maturity stages according to the Brunetti (1990) macroscopic scale.
Figura 4. Estructura de tallas de hembras del calamar argentino Illex argentinus capturadas por arrastreros arrendados en
Brasil entre 2001 y 2003. Las distribuciones de frecuencia de tallas (largo de manto ML en mm) están presentadas por
estratos latitudinales (columna de la izquierda) y estratos batimétricos (columna de la derecha). Los colores diferencian
los estadios de maduración sexual según la escala macroscópica de Brunetti (1990).
417
MALES
Stages
MALES
Stages
I+II
IV+V
VI+VII
I+II
IV+V
VI+VII
FEMALES
FEMALES
Stages
I+II
IV+V
VI+VII+VIII
Stages
I+II
IV+V
VI+VII+VIII
Figure 5. Size structure of Illex argentinus caught by national trawlers off Brazil between 2006 and 2007. Mantle length
frequency distributions (in mm) are presented for males and females by latitudinal (left column) and depth (right column)
strata. Colors differentiate maturity stages according to the Brunetti (1990) macroscopic scale.
Figura 5. Estructura de tallas del calamar argentino Illex argentinus capturados por arrastreros nacionales en Brasil entre
2006 y 2007. Las distribuciones de frecuencia de tallas (largo de manto ML en mm) de machos y hembras están presentadas por estratos latitudinales (columna de la izquierda) y estratos batimétricos (columna de la derecha). Los colores diferencian los estadios de maduración sexual según la escala macroscópica de Brunetti (1990).
females > 260 mm ML). Male size-at-maturity was
estimated to be 163.3 mm ML and 211.8 mm ML for
the smaller and larger modal groups, respectively (Fig.
8). In females, size-at-maturity was estimated to be
201.3 mm ML for the smaller modal group and 292.3
mm ML for the larger one.
The overall maturity condition of the squid in the
catches oscillated in space and time (Fig. 9). The GSI
variability in males and females indicated that gonads
and accessory organs tended to be relatively larger in
the second half of the year in both central and northern
latitudinal strata. In the southern areas, however, they
enlarged earlier, reaching a maximum in autumn. A
similar pattern was also revealed by the Hayashi index, which expresses the advanced maturity condition
when values are low (Table 2, Fig. 9).
Sex ratio and mating activity
Overall catches during the 2001-2003 period were
slightly but significantly biased towards males
(male/female ratio = 1.1; p = 0.001) (Table 3). Season,
latitudinal, and depth strata, however, significantly
affected this general pattern, particularly as females
tended to outnumber males in winter months, both in
shallow areas (< 250 m) and along the central latitudinal stratum (Table 3). A contrasting scenario characterized the 2006-2007 samples: females dominated all
spatial and temporal situations except in the northern
areas (Table 3).
Spermatophore production and storage increased in
stage IV males and peaked in fully mature males
(stage V) (Table 2). Mating activity was evidenced in
the subsequent maturity stages by a sharp decrease in
the presence of spermatophores in the Needhan’s sac.
Similarly, mated females (evidenced by the presence
of spermatophores inside the mantle) were generally
scarce in the catches obtained between 2001-2003
period (not mated/ mated female ratio = 1.8) (Table 4)
except in winter months and > 400 m depths between
25°-29°S, where the opposite pattern was observed.
On the other hand, mated females largely dominated
landings in 2006-2007 (Table 4).
418
Figure 6. Annual distribution of mantle length (ML in mm) (right column) and maturity stages (left column) of the Argentine squid Illex argentinus in commercial catches off Brazil. a and b, males; c and d, females. Size distributions are
represented by cumulative frequencies.
Figura 6. Distribución anual de tallas (largo de manto ML en mm) (columna de la derecha) y estadios de maduración
sexual (columna de la izquierda) del calamar argentino Illex argentinus en capturas comerciales en Brasil. a y b, machos;
c y d, hembras. Las distribuciones de tallas están representadas por las frecuencias cumulativas.
Stock differentiation
The association among squids caught by trawlers between 2001-2003 was analyzed from the scores produced by the first three PCA extracted factors (axes)
that, together, explained 63% and 72% of the total
variance in males and females (Table 5). In males,
factor 1 was defined mainly by geographical variables
(lat, long) and squid size (BW) (higher positive and
negative weights, respectively). Consequently, in the
graphic representation (Fig. 10), large mature males
caught at southwesterly sites should be plotted on the
left hemiplane, whereas small mature squid caught at
northeasterly sites should appear in the right hemiplane. Depth and maturity condition, as expressed by
the Hayashi Index (HI), were particularly important in
factor 2 (Table 5); males caught in deep areas with
enlarged accessory reproductive organs (i.e.
Needham’s sac loaded with spermatophores) should
be plotted on the left hemiplane and small mature
males caught in shallower areas on the right one (Fig.
10). Factor 3 was highly influenced by seasonality,
being mostly defined by the day-of-the-year (DYR)
(Table 5); squid caught in spring and summer should
be plotted in the extremes of the upper and lower
hemiplanes, respectively, whereas autumn-winter
squids should appear near the center of the axis (Fig.
10). A similar spatial scenario resulted from the three
factors obtained with female variables except that
factor 2 was also highly influenced by maturity indices (GSI and NGI) and high loads for the depth
(DEPTH) variable were placed in factor 3 (Table 5).
In the spatial representation of both males and females, a large group of squid corresponded to small
mature animals caught throughout the year in shallower areas of the northeastern slope. In contrast, a
smaller group of both sexes, detached from the former
419
Table 2. Summary of the maturity conditions of the Argentine shortfin squid Illex argentinus in commercial trawl catches
off Brazil between 2001 and 2007. Examined males and females were pooled by maturity stages (after Brunetti, 1990)
and the relative and cumulative frequencies of each stage were calculated and expressed in percentages (% and Cum.%
respectively). The largest (Max) and smallest (Min) mantle length of squid in each maturity stage are indicated. Males
with no, few, and many spermatophores (spermat.) in the Needhan’s sac and females with and without spermatophores at
the base of the gills were also quantified for each maturity stage.
Tabla 2. Resumen de las condiciones de madurez sexual de calamar argentino Illex argentinus en capturas comerciales de
la pesca de arrastre en Brasil entre 2001 y 2007. Los machos y hembras examinados fueron agrupados por estadios de
madurez (según Brunetti, 1990). Para cada estadio se calcularon las frecuencias relativas y acumuladas expresadas en
valores porcentuales (% y Cum.% respectivamente). Para cada estadio de madurez sexual se indica la longitud máxima
(Max) y mínima (Min) del manto. También se contaron para cada estadio de madurez los machos con ninguno, pocos o
muchos espermatóforos (spermat.) en la bolsa de Needhan y las hembras con y sin espermatóforos en las bases de las
branquias.
Maturity stages
Immature+Maturing
Mature
Spawning+Spent
I
II
III
IV
V
VI
VII
VIII
Total
N
%
Cum.%
108
3.6
3.6
286
9.6
13.3
517
17.4
30.7
621
20.9
51.6
535
18.0
69.6
728
24.5
94.1
174
5.9
100.0
-
2969
ML
Max
Min
199
78
218
100
254
102
260
111
316
122
340
110
302
131
GSI
Mean
(SE)
1.02
(0.11)
1.93
(0.10)
3.56 4.86 5.58 5.09 4.27
(0.10) (0.12) (0.07) (0.08) (0.31)
HI
Mean
(SE)
0.60
(0.02)
0.65
(0.01)
0.72 0.64 0.46 0.51 0.43
(0.01) (0.01) (0.01) (0.01) (0.02)
N
%
Cum. %
109
11.9
11.9
286
31.2
43.1
517
56.4
99.6
0
0.0
99.6
2
0.2
99.8
1
0.1
99.9
1
0.1
100.0
-
916
No spermat.
N
%
Cum. %
0
0.0
0.0
0
0.0
0.0
0
0.0
0.0
625
38.9
38.9
3
0.2
39.1
791
49.2
88.2
189
11.8
100.0
-
1608
Few spermat.
N
%
Cum. %
0
0.0
0.0
0
0.0
0.0
0
0.0
0.0
0
0.0
0.0
540
0
0
100.0 0.0
0.0
100.0 100.0 100.0
-
540
Many spermat.
N
%
Cum. %
183
6.5
6.5
365
13.0
19.5
344
12.2
31.7
366
13.0
44.7
383
13.6
58.3
643
22.8
81.1
399
14.2
95.2
ML
Max
Min
205
91
213
115
277
124
299
104
334
105
351
242
395
262
367
120
GSI
Mean
(CE)
2.4
(0.7)
2.6
(0.3)
3.7
(0.2)
13.6
(0.4)
25.2
(0.8)
25.1
(0.4)
19.5
(0.5)
16.0
(0.9)
HI
Mean
(CE)
0.51
(0.01)
0.48
(0.01)
0.48 0.46 0.38 0.30 0.27 0.20
(0.01) (0.01) (0.01) (0.00) (0.01) (0.02)
N
%
Cum. %
183
11.1
11.1
368
22.3
33.4
347
21.0
54.4
370
22.4
76.8
383
23.2
99.9
0
0.0
99.9
0
0.0
99.9
1
1652
0.1
100.0
N
%
Cum. %
0
0.0
0.0
0
0.0
0.0
1
0.1
0.1
1
0.1
0.1
2
0.1
0.3
665
49.1
49.4
529
39.1
88.5
157 1354
11.6
100.1
Males
Females
Mated
Non-mated
340
78
134 2817
4.8
100.0
395
91
420
Figure 7. Size distribution (mantle length in mm) of the
Argentine squid Illex argentinus caught by commercial
trawlers off Brazil between 2001-2007 according to
sexual maturity stages (defined following Brunnetti,
1990). a) males, b) females.
Figura 7. Distribución de tallas (largo de manto ML en
mm) del calamar argentino Illex argentinus capturado
por arrastreros comerciales en Brasil entre 2001-2007
según estadio de maduración sexual (definidos según
Brunetti, 1990). a) machos, b) hembras.
group, was composed of large mature animals caught
in deep southwestern areas during a restricted period
in the middle of the year (winter) (Fig. 10).
DISCUSSION
Interpreting the biological patterns of I. argentinus
from commercial catches off Brazil requires the initial
consideration that these patterns may combine the
Figure 8. Mantle length (ML) cumulative frequency
distribution of mature males (a) and females (b) Argentine squid Illex argentinus caught by commercial trawlers
off Brazil between 2001 and 2007 (dark blue symbols).
ML-at-maturity of two modal classes are indicated for
both sexes as calculated after the probit transformation of
frequencies (light blue symbols).
Figura 8. Distribución acumulada de tallas (largo de
manto ML en mm) de machos (a) y hembras (b) sexualmente maduras del calamar argentino Illex argentinus
capturado por arrastreros comerciales en Brasil entre
2001 y 2007 (puntos azules oscuros). ML del inicio de la
maduración sexual de las dos clases modales están indicados para los dos sexos según estimados por la transformación probit de frecuencias (puntos azules claros).
mixed effects of three critical sources: (a) existing
biologically distinct population units that may exhibit
particular spatial/ temporal distribution patterns, (b)
non-random spatial/ temporal fishing strategies that
may or may not include squid as a principal target, and
(c) on board discards (at least for the national trawl
fleet). The two latter sources of bias limit our capacity
to comprehensively address the entire population diversity of the species in Brazilian waters. On the other
hand, it is possible to conclude, by confronting bio-
421
Figure 9. Seasonal and latitudinal variability of maturity indices of the Argentine shortfin squid Illex argentinus caught
by commercial trawlers off Brazil between 2001 and 2003. Symbols represent median values and vertical bars represent
standard errors. a and c, males; b and d, females.
Figura 9. Variabilidad temporal y latitudinal dos los índices de madurez sexual del calamar argentino Illex argentinus
capturado por arrastreros comerciales en Brasil entre 2001 y 2003. Símbolos representan valores medianos y líneas verticales representan error estándar. a y c, machos; b y d, hembras.
logical patterns of the catches with synoptic descriptions of the Illex population structure as produced by
preceding trawl surveys (Haimovici & Perez, 1990,
1991; Santos & Haimovici, 1997), that different
spawning groups can be identified in the commercial
catches and, more importantly, that the availability/vulnerability of these groups and their specific
biological features may have influenced the trawl
fishing patterns on the slope off southern Brazil (Perez
& Pezzuto, 2006; Perez et al., 2009b).
Samples of commercial catches obtained between
2001-2003 contained immature and maturing squid
throughout the year, as well as at least two distinguishable fully mature-spawning groups. The first
group, composed of small-sized males and females,
was present during all seasons on the shelf-break/
upper slope (< 400 m). In winter-spring, however, a
distinctive group of large squid dominated the catches
in southern (south of 28°S) and deep fishing grounds
(400-700 m). Both groups had been previously identified in trawl surveys off southern Brazil, the latter
being specifically referred to as the southern Brazil
stock (SBS) (Haimovici et al., 1998). In the present
study, this group was shown to sustain the exceptionally large catches obtained by the chartered trawler “In
Sung 270” in September 2001 and also the winter
catches produced by national trawlers, mostly from
2003 onwards (Perez & Pezzuto, 2006; Perez et al.,
2009b). Unlike the upper slope concentrations of
small squid, it seems evident that these large individuals, seasonally available in dense concentrations on
the lower slope, attracted the attention of the fishing
industry and became valued targets of the developing
multispecies deep-water trawl fishery off southern
Brazil (Perez & Pezzuto, 2006; Perez et al., 2009b). A
relevant issue regarding this pattern, however, has
been the fact that SBS squid could actually be connected to the Patagonian shelf stocks through spaw-
422
Table 3. Sex ratio of the Argentine shortfin squid Illex argentinus in commercial trawl catches off Brazil in two periods:
2001-2003 and 2006-2007. M/F: male/ female ratio, p: probability (Π2). Values in bold correspond to probabilities obtained by contingency table analysis to compare the effects of trimesters, depth, and latitudinal strata on the sex-ratio.
Table 3. Proporción de sexos del calamar argentino Illex argentinus en capturas de la pesca comercial de arrastre en Brasil en dos periodos: 2001-2003 y 2006-2007. M/F: fracción número de machos / número de hembras; p: probabilidad
(Π2). Valores en negrita corresponden a probabilidades resultantes del análisis de la tabla de contingencia para comparar
los efectos de trimestres, estratos batimétricos y estratos latitudinales sobre la proporción sexual.
2001-2003
Trimester Males Females M/F
2006-2007
p
Males Females M/F
p
Jan-Mar
Apr-Jun
Jul-Sep
553
846
292
453
971
433
1.2 0.002
0.9 0.003
0.7 < 0.001
0
164
126
0
308
155
0.5 < 0.001
0.8 0.084
Oct-Dec
p
1011
610
1.7 < 0.001
73
77
0.9
< 0.001
0.002
Depth strata
< 250 m
224
313
0.7 < 0.001
46
60
0.8
250 - 400
> 400 m
1992
450
1822
288
1.1 0.006
1.6 < 0.001
145
172
214
266
0.7
0.6
p
< 0.001
Latitudinal strata
North
2015
0.74
0.736
1537
1.3 < 0.001
77
57
1.4
0.137
Centre
South
p
483
144
741
78
0.7 < 0.001
1.8 < 0.001
< 0.001
25
226
101
338
0.2 < 0.001
0.7 < 0.001
< 0.001
Total
2702
2467
1.1
363
540
0.7
ning migrations and paralarval transport, as described
for other ommastrephid species elsewhere (Hatanaka
et al., 1985). If confirmed, this hypothesis would directly characterize a shared stock scenario with important implications for management in Argentina, Uruguay, and Brazil (Haimovici et al., 2007).
Population connections between I. argentinus occurring in the SW Atlantic were formerly addressed
by Brunetti (1988), who defined three major stocks
occurring off the coast of Argentina and Uruguay
(SSS, SPS, and BNS) and concluded that squid distributed along southern Brazil were an extension of
the northernmost stock (BNS). Because partly
spawned or spent squid were never observed in BNS
catches, the spawning location remained uncertain but
was speculated to occur between July and September
somewhere offshore, north of 38°S, under the Falkland (Malvinas) or Brazil Currents. Santos & Haimovici (1997) analyzed reproductive patterns of the
0.001
0.002
previously considered SBS members and also concluded that these squid were, in fact, members of
BNS, but proposed alternatively that southern Brazil
was their major winter-spring spawning ground. Taking into consideration records of elevated concentrations of I. argentinus paralarvae under the core of the
Brazil Current (Haimovici et al., 1995) and other evidence derived from trophic relations, parasites, and
body proportions (Santos, 1992), Santos & Haimovici
(1997) further postulated that maturing BNS squid
would migrate in early winter from northern Argentina
to southern Brazil slope waters, where spawning
would take place under the warm Brazil Current. During spring-summer, as the Subtropical Convergence
retracted, egg masses and paralarvae would be transported southwards, allowing recruitment to occur on
the southern feeding grounds off northern Argentina
(Haimovici et al., 1998). Whereas this hypothesis still
requires corroboration through high-resolution me-
Figure 10. Spatial representation of males (a) and females (b) of the Argentine shortfin squid Illex argentinus
caught by commercial trawlers off Brazil between 2001
and 2003 according to the values generated by the first
three factors obtained with Principal Component Analysis. The green line indicates small-sized mature squid
caught all year round on the upper slope. The red line
indicates large-sized mature squid caught in winter at
depths over 400 m.
Figura 10. Representación espacial de machos (a) y
hembras (b) de calamar argentino Illex argentinus capturado por arrastreros comerciales en Brasil entre 2001 y
2003 según los valores generados por los tres primeros
factores obtenidos con el Análisis de Componentes Principales. La línea verde indica el grupo de calamares
sexualmente maduros de pequeño tamaño capturado a lo
largo del año en el talud superior. La línea roja indica el
grupo de calamares sexualmente maduros de mayor tamaño capturado en los meses de invierno a profundidades mayores de 400 m.
423
thods such as tagging experiments or genetic markers,
the biological data from commercial catches off
southern Brazil may provide further indirect evidence
in its support.
Initially, the sizes of mature squid present in winter
catches off Brazil resembled those reported for members of both BNS and SBS, although precise comparisons were not possible because the different studies
included different maturity stages for estimating sizeat-maturity. Nonetheless, mantle lengths of males and
females of these groups were noticeably larger than
those estimated for a presumably “local” upper -slope
stock, suggesting that these squid were, in fact, biologically distinct (Table 6). Schwarz & Perez (2007)
analyzed the morphology and morphometry of statoliths extracted from squid caught by commercial
trawlers off Brazil and reached similar conclusions.
Secondly, the majority of the squid present in the
winter catches off Brazil were mated females in a
spawning-spent condition, indicating that fishing was
concentrated on a spawning event that could be related
to a) the spawning seasons proposed for BNS and SBS
and b) the spawning grounds proposed for the latter,
namely the slope area between 27°S and 34°S (Brunetti, 1988; Santos & Haimovici, 1997) (Table 6).
Within these grounds, commercial catches further
revealed that large spawning squid concentrated in
high densities during the day on the deep slope (400700 m). This pattern was also observed by both fishing and acoustic surveys conducted between 2001 and
2002, which further associated spawning squid concentrations with temperature ranges between 7° and
13°C (Madureira et al., 2005; Haimovici et al., 2008).
The deep, cold environment off southern Brazil is
generally associated with the influence of South Atlantic Central Water (SACW), which flows southwards over the slope as a deep layer of the Brazil Current (Castro et al., 2006). Temperature and salinity
within this water mass range from 6-20°C and 34.636.0, respectively, characterizing a considerably
colder, less saline environment than that of the overlaying Tropical Water, which is also transported, although superficially, by the Brazil Current. Considering that (a) spawning squid from the Patagonian shelf
may require an optimal thermal environment ranging
from 4° to 13°C (Brunetti et al., 1998) and (b) that
pre-reproductive BNS members at the ArgentineUruguayan Common Fishing Zone (34º00'- 39º30'S)
were shown to concentrate in subantarctic waters between 4-10ºC (Bazzino et al., 2005), it seems reasonable that a spawning migration towards Brazilian waters (Santos & Haimovici, 1997) would take place in
association with deep water masses such as SACW. A
final element in support of a connection between Bra-
424
Table 4. Evidence of mating in female Argentine shortfin squid Illex argentinus caught in commercial trawl catches off
Brazil in two periods: 2001-2003 and 2006-2007. N/M: not mated/mated female fraction, p-values correspond to probabilities obtained by contingency table Π2 analysis to compare the effects of trimesters, depth, and latitudinal strata on the
mated condition of females.
Tabla 4. Evidencias de cópula en hembras de calamar argentino Illex argentinus capturado por la pesca comercial de
arrastre en Brasil en dos periodos: 2001-2003 y 2006-2007. N/M: fracción no-copuladas/copuladas. P: probabilidades
resultantes del análisis Π2 para comparar los efectos de trimestres, estratos batimétricos y estratos latitudinales sobre la
actividad de cópula de las hembras.
2001-2003
Trimester
Jan-Mar
Apr-Jun
Jul-Sep
Oct-Dec
p
Depth Strata
< 250 m
250 - 400
> 400 m
p
Latitudinal strata
North
Centre
South
p
Total
p
2006-2007
Not-mated
Mated
N/M
Not-mated
Mated
N/M
339
752
67
423
114
219
366
187
<0.001
3.0
3.4
0.2
2.3
20
26
25
288
128
52
<0.001
0.1
0.2
0.5
150
1281
107
163
541
181
<0.001
0.9
2.4
0.6
6
39
26
54
175
239
0.019
0.1
0.2
0.1
1201
262
47
336
479
31
<0.001
886
<0.001
3.6
0.5
1.5
23
9
38
0.7
0.1
0.1
1.8
71
34
92
299
<0.001
468
<0.001
1581
zilian and Patagonian squid stocks can be drawn from
the combination of the commercial value of “big
squid”, the opportunistic behavior of the trawl fishery,
and the general evolutionary population strategies of
ommastrephid squids (O’Dor, 1992). These squids
normally exhibit complex population structures in
association with geostrophic currents, protracted
spawning, and latitudinal migrations as a strategy to
spread – over space and time – the risks of their short,
semelparous life cycle (O’Dor, 1998). Because cold,
nutrient-enriched temperate waters tend to delay maturity and enhance survivorship of juvenile squid,
stocks whose offspring drift, carried by geostrophic
currents, to these waters attain larger sizes, are more
abundant, and sustain larger fisheries (e.g. I. illecenbrosus, O’Dor & Coelho, 1993; Perez & O’Dor,
1998). Although these squid need to perform long
migrations, their large body size favors swimming
long distances (O’Dor, 1988). In contrast, those stocks
that remain in food-poorer, warmer, tropical and sub-
0.2
tropical waters tend to grow fast but also to mature
early at smaller sizes (O’Dor & Coelho, 1993). In a
less productive environment, these squids are also less
abundant and sustain significantly lower annual landings.
By experiencing their early life in a highly productive and cold environment such as the Patagonian
Shelf, BNS squid would tend to be abundant (actually
sustaining large catches in the northern Patagonian
Shelf) and to mature late in life at large sizes, fit for a
~2,000-km-long winter spawning migration towards
Brazilian waters. Because these are cold-water squid,
they would tend to reach the deep layers of the slope
as they approach southern Brazil, concentrating within
the 300-400-m-high SACW layer (Madureira et al.,
2005; Castro et al., 2006) and, hence, becoming vulnerable to the slope trawling in winter and earlyspring. Off southern Brazil during this period of the
year, winter spawners should be markedly distinct
from the “local” spawners, both by their larger body
425
Table 5. Principal Component Analysis employed to differentiate Argentine shortfin squid Illex argentinus stocks within
the catches obtained by commercial trawlers off Brazil between 2001 and 2003. Variables included were: day-of-the-year
(DYR), decimal latitude (LAT), decimal longitude (LONG), depth (DEPTH), body wet weight (BW), gonadosomatic
index (GSI), Hayashi index (HI), Nidamental gland/ Testis Index. The linear coefficients of the variables (loadings) in the
first three factors rotated by the PCA are indicated for males and females. The eigenvalues and the variance explained by
each factor are indicated in the last three rows.
Tabla 5. Análisis de Componentes Principales aplicada en la diferenciación de los stocks de calamar argentino Illex argentinus en las capturas de arrastreros comerciales en Brasil entre 2001 y 2003. Las variables incluidas fueron: día-delaño (DYR), latitud decimal (LAT), longitud decimal (LONG), profundidad (DEPTH), peso húmedo del cuerpo (BW),
índice gonadosomático (GSI), índice de Hayashi (HI), índice de la glándula nidamental/ testículo. Los coeficientes lineales de las variables (pesos) en los tres primeros factores rotacionados por el PCA se indican para machos y hembras. Los
valores propios y la varianza explicada por cada factor se indican en las últimas tres líneas.
DYR
1
-0.105
Males
Factor
2
-0.051
3
0.846
LAT
0.929
0.157
0.090
0.952
0.031
0.084
LONG
0.896
0.306
0.102
0.940
0.117
-0.008
DEPTH
-0.006
0.694
-0.163
0.105
0.445
-0.686
BW
-0.699
0.358
-0.020
-0.737
0.059
-0.282
GSI
0.149
0.310
0.453
0.027
0.873
0.114
HI
0.425
-0.683
-0.213
0.363
-0.685
0.014
NGI / TI
0.185
0.392
-0.427
0.128
0.766
0.263
Eigenvalue
2.403
1.447
1.195
2.639
2.037
1.079
Variance explained (%)
30.035
18.087
14.933
32.983
25.461
13.483
Cum. variance explained (%)
30.035
48.122
63.055
32.983
58.444
71.927
Component
Females
Factor
1
2
-0.379
0.043
3
0.662
Table 6. Summary of characteristics of two stocks of the Argentine shortfin squid Illex argentinus in waters of the northern Patagonian shelf (BNS) and southern Brazil (SBS) in comparison with spawning groups differentiated in the commercial trawl catches off southern Brazil between 2001 and 2007. Sizes at maturity refer to modal mantle lengths of males
and females in different maturity stages (between parentheses) as defined by Brunetti (1990).
Tabla 6. Resumen de las características de dos stocks de calamar argentino Illex argentinus en el norte de la plataforma
patagónica (BNS) y el sur de Brasil (SBS) en comparación con los grupos desovantes diferenciados en las capturas comerciales de pesca de arrastre en el sur de Brasil entre 2001 y 2007. La talla de madurez sexual corresponde a la longitud
modal del manto de machos y hembras en diferentes estadios de madurez (entre paréntesis) definidos por Brunetti (1990).
Proposed stocks
Spawning Grounds
Spawning season
Modal size at
maturity (ML)
1
Commercial catches off Brazil
Bonaerensis-north
patagonic (BNS)1
Southern
Brazil (SBS) 2
Large
spawners3
Small
spawners3
Slope, north of 38°S,
under the Falkland/
Malvinas Current or
Brazil Current
Slope, between 27°S
and 34°S under the
Brazil Current
Between 26° and 29°S,
360-520 m depth
North of 28°S,
shallower than 360
m depth
July – September
July – November
July - September
All year-round
Males: ~200 mm
Females: ~240 mm
(Stages IV+V)
Males: ~250 mm
Females: ~300 mm
(Stages > V)
Males: 212 mm
Females: 292 mm
(Stages > IV)
Males: 161 mm
Females: 201 mm
(Stages > IV)
Brunetti et al. (1991), 2Santos & Haimovici (1997), 3This study.
426
size and their deeper bathymetric distribution, attracting the attention first of the highly efficient and exploratory foreign chartered trawlers (Perez et al.,
2009b) and later the more conservative but overcapitalized national trawl fleet (Perez & Pezzuto, 2006). In
2002, trawler skippers persistently tried to convince
fishing biologists involved with this study that their
large catches off Brazil were, in fact, a different squid
species due to their obviously different body proportions and suggested that it be given a new name as a
marketing strategy (Perez pers. observ.). Albeit anecdotal, this fact highlights the effect of the diversity of
this species population (and particular biological attributes) on the observed exploitation patterns in the
SW Atlantic, reinforcing the need to consider multinational, shared stock management strategies in the region. Other shellfish and finfish resources exploited in
the deep waters off southern Brazil (e.g. deep-water
crabs, hake, and others) seem to justify the same
strategies (Perez et al., 2009a).
ACKNOWLEDGEMENTS
The authors are indebted to all observers, captains,
and crews that allowed this large body of data to be
collected during their commercial operations off
southern Brazil. We also thank Rodrigo Sant’Ana for
invaluable help with figures. Funding for this study
was provided by the Special Secretariat for Aquaculture and Fisheries (SEAP/PR/027/2007) and the National Council for Scientific and Technological Development (CNPq) research grant (Process
306184/2007-9).
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428
Lat. Am. J. Aquat. Res., 37(3): 429-442, 2009
Sexual maturity of Chaceon notialis
429
Research Article
Sexual maturity of the deep-sea red crab Chaceon notialis Manning & Holthuis,
1989 (Brachyura: Geryonidae) in southern Brazil
1
Rodrigo Sant’Ana1 & Paulo Ricardo Pezzuto1
Rua Uruguai 458, CEP 88.302-202, Itajaí, SC, Brazil
ABSTRACT. The red crab Chaceon notialis is one of the three deep-sea crab species currently exploited in
Brazil. The red crab fishery started in 1998 with foreign vessels that, as of 2000, have been extensively monitored by observers and tracked by satellite. A management plan implemented in 2005 was based only on biomass dynamics, as biological knowledge of the resource was limited at that date. Samples taken aboard were
used to determine size at first sexual maturity for males and females by studying the allometric growth of the
chelae and abdomen in relation to the carapace width (CW), the proportion of females with opened vulvae and
eggs in the pleopods, and males showing copula marks on the first ambulatory legs. Morphometric maturity
was attained, on average, at 8.9 cm CW (males) and 8.8 cm CW (females). The CW50% was estimated to be 6.9
and 9.7 cm CW for females, considering the vulva condition and eggs in the pleopods, respectively, and 8.4
cm CW for males. The maximum estimated proportions of ovigerous females and males with copula marks by
size class were 0.8 and 0.7, respectively, suggesting an annual reproductive cycle for the species, both at the
populational and individuals levels. The size composition analysis showed that up to 97% of the females
caught in the fishery were immature. Given these results, enhancing trap selectivity and minimizing the mortality of ovigerous females should be considered as new and immediate goals for the management of the resource.
Keywords: reproduction, trap fisheries, relative growth, sexual maturity, Geryonidae, Chaceon notialis, Brazil.
Madurez sexual del cangrejo rojo de profundidad Chaceon notialis
Manning & Holthuis, 1989 (Brachyura: Geryonidae) al sur de Brasil
RESUMEN. El cangrejo-rojo Chaceon notialis corresponde a una de las tres especies de cangrejos de
profundidad que actualmente se explotan en Brasil. La pesca de cangrejo-rojo comenzó en el año 1998 por
barcos extranjeros que, desde 2000 fueron intensamente vigilados por observadores y rastreados por
satélites. En el año de 2005 se implementó un plan de manejo, considerando solamente el estudio de la
dinámica de la biomasa del recurso, ya que el conocimiento biológico todavía era limitado. A partir de
muestras obtenidas a bordo de los barcos de pesca, se estimó la talla de primera madurez de machos y hembras
mediante la utilización del crecimiento alométrico de la quela y el abdomen, con respecto al ancho del
caparazón (CW), proporción de hembras con vulvas abiertas y huevos en los pleópodos y machos con marcas
de cópula en las primeras patas ambulatorias. La madurez morfométrica para los machos fue obtenida en
promedio a 8,9 cm de CW y para las hembras a 8,8 cm de CW. El CW50% fue estimado en 8,4 cm para machos
y para hembras, tomando en cuenta la condición de la vulva o los huevos en los pleópodos, en 6,9 y 9,7 cm
respectivamente. Las máximas proporciones estimadas de hembras ovígeras y machos con marcas de cópula
por talla fueron de 0,8 y 0,7 respectivamente, lo que sugiere que el ciclo reproductivo a nivel poblacional e
individual es anual. El análisis de la composición de tallas indicó que el 97% de las hembras capturadas, eran
inmaduras. A partir de estos resultados se consideró un aumento en la selectividad de las trampas y la
430
disminución de las hembras ovígeras en las capturas como objetivos nuevos e inmediatos para el mejor manejo
de este recurso.
Palabras clave: reproducción, pesca con trampas, crecimiento relativo, madurez sexual, Geryonidae, Chaceon
notialis, Brasil.
________________________
Corresponding author: Paulo Ricardo Pezzuto ([email protected])
INTRODUCTION
The red crab Chaceon notialis is one of two geryonid
crabs known from the southwestern Atlantic Ocean.
The species inhabits slope grounds off Brazil, Uruguay, and Argentina, between 120 and 1000 m depth
(Manning & Holthuis, 1989; Pezzuto et al., 2002;
Delgado & Defeo, 2004).
In the late 1970s, investigations undertaken by the
National Fishery Institute identified a potentially harvestable stock of the species in Uruguay (Niggermeyer
et al., 1990). Red crab assessments conducted in the
middle 1980s along the Uruguayan EEZ estimated an
exploitable biomass of nearly 22,000 ton, corresponding to one of the highest geryonid stocks known in the
whole world ocean (Defeo et al., 1991). A directed
fishery for the species emerged in that country as of
1995, attaining annual landings of up to 4,102 ton
since (Delgado & Defeo, 2004).
In Brazil, the first commercial exploitation of red
crabs dates from 1984 and 1985, when an exploratory
fishery was conducted by two Japanese vessels near
the border of the Brazilian and Uruguayan EEZs
(Lima & Lima-Branco, 1991). Only after 1998 did the
species become the target of a fully developed fishery
carried out by another Japanese vessel (F/V Kinpo
Maru 58) in the same region. Completely export oriented, this fishery yielded a total of 7,347 ton (live
weight) between 1998 and 2006, with annual landings
varying between 303 and 1,378 ton (Pezzuto et al.,
2006b).
This vessel was intensively monitored by observers
and satellite vessel monitoring systems (VMS), producing a large fishery-based data set that was used to
identify the species distribution and to generate preliminary estimates of stock biomass and maximum
sustainable yield (Pezzuto et al., 2002, 2006b). A
management plan for the red crab fishery was established in May 2005, based mostly on the biomass
dynamics of the stock, including a total allowable
catch (TAC) (1,050 ton live weight year-1, corresponding to the Maximum Sustainable Yield), maximum
number of permits (two vessels), and minimum mesh
size in the traps (100 mm stretched). Biological measures such as minimum legal sizes, closed areas/seasons, or sex-selective harvest strategies would
have been considered in the plan but no life-cycle
parameters were available for the species at the time,
even though biological data had been intensively collected aboard by the observers.
At the present time, information about the species
is relatively scarce and includes biomass assessments
(Defeo et al., 1991; Pezzuto et al., 2002), fishing dynamics (Defeo & Masello, 2000a, 2000b; Athiê &
Rossi-Wongtschowski, 2004), contributions to the
feeding of demersal fishes (Peres & Haimovici, 2003),
management (Pezzuto et al., 2006a), diet (Domingos
et al., 2007), and size at the onset of morphological
and functional maturity of females caught in Uruguayan waters (Delgado & Defeo, 2004). No information about the maturity of females is available for the
Brazilian part of the stock or for males exploited anywhere.
Given their high value and k-strategist life-traits,
geryonid crabs are expected to be highly vulnerable to
overexploitation, requiring severe fishing regulations
for their sustainability (see review by Hastie, 1995).
Like biomass estimates and population structure data,
knowledge about reproductive features can give the
necessary support to develop management tactics
intended to ensure appropriate biomass renewal rates
for these fragile crabs. Size-at-maturity is, therefore,
one of the most important biological parameters used
for management purposes and has been widely studied
in several Geryonid stocks (e.g. Haefner, 1977; Beyers
& Wilke, 1980; Erdman & Blake, 1988; Attrill et al.,
1991; Fernández-Vergaz et al., 2000; Delgado & Defeo, 2004; Pezzuto & Sant’Ana, 2009).
Considering the need to improve the red crab management plan with biological reference points, this
paper investigates the sexual maturity of C. notialis
vulnerable to a directed fishery in southern Brazil and
analyzes the annual size-structure of the catches, quantifying the contribution of immature and mature individuals to the fishery.
Data source and sampling
Maturity analyses were carried out with biological
data collected by observers during 19 commercial trips
conducted between 2001 and 2005 by the F/V Kinpo
Maru 58, a 63-m-long factory vessel. This vessel
fished in Brazilian waters from September 1999 to
November 2007. It operated four sets of ground lines
simultaneously; 450 ± 16 (SD) cylindrical-conical
traps were attached to each line. The traps were spaced
regularly at 18 m and measured 140 cm (Ø) at the
base, 73 cm (Ø) at the top, and 65 cm in height; they
were rigged with a 100-mm (stretched) mesh. The
mean soak time was 38 h (Pezzuto et al., 2002,
2006a).
Observers recorded, for all hauls, the date, position, depth, number of traps line-1, soak time, catch
haul-1 (kg), and the mean number of crabs trap-1. During the study period, nearly 41,000 crabs were sampled aboard within the main fishing ground of the
species (i.e. 31o to 35°S and 100 to 1,000 m depth)
(Table 1, Fig. 1).
Biological sampling was carried out on hauls especially selected by the observers in order to cover different depths and latitudes according to the commercial fishing strategy used by the vessel’s captain. The
maximum interval between successive samplings was
48 h. All crabs caught in randomly selected traps positioned in the beginning, middle, and end sections of
the main ground line were examined. The sex was
determined and the carapace width (CW; distance
between the fifth antero-lateral spine tips) was measured to the nearest millimeter. Males were classified
according to the presence or absence of copula marks
(blackened areas in the merus of the second pereiopods - (see Melville-Smith, 1987) for 125 hauls. The
vulva condition (i.e. closed/immature or opened/mature; Delgado & Defeo, 2004) and the presence of
eggs in the pleopods were recorded for females sampled from 285 and 180 hauls, respectively. The number of hauls on which such biological features were
observed differed due to female-biased sex ratios in
the catches and seasonal reproduction.
Besides the data collected aboard, additional biological samples (frozen crabs) were regularly obtained
by the observers for detailed laboratory analyses concerning the relative growth of body parts, as logistical
constraints precluded taking new measurements in the
field. In the laboratory, these crabs were measured
(carapace width), sexed, and examined for copula
marks, vulva condition, and the presence of eggs in
the pleopods following the same procedures adopted
431
aboard. In addition, detailed measurements of body
parts were also obtained for relative growth analyses
of secondary sexual characteristics (Hartnoll, 1974,
1982). Measurements were conducted with sliding
calipers to the nearest 0.5 mm and included the abdomen width (AW, measured between the 4th and 5th
abdominal somites), left and right cheliped lengths
(LChL and RChL, maximum length of the upper portion of the propodus), and left and right maximum
cheliped height (LChH and RChH, maximum height
of the propodus measured on its exterior face) for
males and females.
Data analysis
According to Hartnoll (1974, 1982), most brachyuran
crabs exhibit changes in the relative growth of their
secondary sexual characteristics along their ontogeny.
Such changes define the transition between different
growth phases (i.e. pre- and post-pubertal growth) that
occur at the puberty molt. In this paper, the
morphometric maturity of C. notialis was studied by
analyzing the relative growth of 512 crabs processed
in the laboratory (266 males, 246 females). An
allometric equation (Y = a CWb) was fitted to the data
by least squares regression and the transition points
(i.e. changes in slope and/or elevation) were iteratively
searched by a specific routine of the software Regrans
(Pezzuto, 1993). The routine seeks the CW value
where the data could be split into two subsets resulting
in the lowest combined residual sum of squares. A
statistical test for coincidental regressions was
conducted in order to check the validity of the
transition points. The test compared the difference
between the global sum of squares (i.e. calculated
from a single model fitted to the data) and the pooled
residual sum of squares (i.e. from the subsets located
to the left and right sides of the transition point) (Zar,
1996). If a significant difference was found, an
ANCOVA (α = 0.05) was used to test the difference
between the elevations and slopes of the two
regressions (Zar, 1996), which were assumed to
correspond to the pre- and post-pubertal growth
phases (sensu Hartnoll, 1974).
The relative growth pattern (i.e. negative
allometric, isometric, positive allometric) of each
body dimension and phase (pre- and post-pubertal)
was identified by testing the allometric coefficient
(slope) against the reference value “1” (Zar, 1996).
Functional/sexual maturity was also studied by
estimating the mean sizes (CW50%) at which males and
females were able to copulate and reproduce.
Proportions of males showing copula marks and
females with opened vulvae and eggs in the pleopods
432
Table 1. Chaceon notialis. Number of trips, hauls, and crabs sampled aboard the F/V Kinpo Maru 58 on the slope of
southern Brazil for the size at maturity analysis.
Tabla 1. Chaceon notialis. Número de viajes, lances de pesca y cangrejos muestreados a bordo del F/V Kinpo Maru 58 en
el sur de Brasil para el análisis de la madurez sexual.
Year
Trips
Hauls
Males
Females
Total
Depth range (m)
2001
4
85
5,379
16,097
21,447
326 - 830
2002
4
83
2,156
4,842
6,999
182 - 970
2003
4
99
1,268
2,865
4,134
357 - 844
2004
4
112
2,073
4,183
6,257
264 - 901
2005
3
74
867
2,042
2,909
325 - 835
Total
19
451
11,744
30,030
41,774
182 - 970
Figure 1. Map showing the main fishing area of Chaceon notialis in southern Brazil during the study period (gray area).
Isobaths of 100, 200, 500, and 1000 m are indicated.
Figura 1. Mapa de la área principal de pesca de Chaceon notialis en el sur de Brasil durante el período de estudio (área
gris). Se indican las isóbatas de 100, 200, 500 y 1000 m.
were calculated for 1-cm size (CW) classes,
considering the total number of individuals caught
during the hauls sampled aboard. The total numbers in
the catches were previously estimated by multiplying
the numbers in the samples by the ratio between the
total catch weight and the sample weight. Proportions
of ovigerous females were analyzed only for trips
carried out between July and December, the main
reproductive season of the species (Pezzuto et al.,
2006b).
A non-linear minimum squares estimation procedure was then used to fit a generalized logistic model
(Restrepo & Watson, 1991) to the data as follows:
PCW =
β
1 + e( α1 −α 2CW )
(1)
where PCW is the proportion of individuals in each size
class and α1, α2, and β are parameters. In this model,
β is a more general parameter that allows for the asymptotic proportion of the model to be lower or equal
to 1. Therefore, a penalty function for β ≤ 1 was included in the parameter estimation procedure. This is
of special interest for management purposes as it can
indicate the maximum theoretical proportion of individuals presenting the maturity criteria in the largest
size classes in a given period/study area. Size at 50%
maturity was given by the equation:
α
CW50% = 1
α2
(2)
Confidence intervals for CW50% were estimated by
a bootstrap procedure in which frequency distributions
of individuals with copula marks, opened vulvae, and
eggs in the pleopods were randomly resampled 250
times, resulting in a corresponding number of logistic
curves for each case. Given the asymmetrical distribution of the results, the medians of the 250 CW50% estimates were calculated and the 2.5 and 97.5% percentiles used as 95% confidence intervals (CI) (Haddon,
2001).
The size-structure of the global catches was studied
using information collected by the observers during all
trips. It was analyzed by sex in terms of the proportion
of mature and immature individuals fished per year
and considering the total number of individuals sampled aboard in the period. Before pooling the data
from several trips and hauls, numbers sampled by size
class and sex were raised to the total caught in the
respective hauls following the same procedure described in the functional/sexual maturity analysis.
Weighted averages (and the respective 95% CI) of
the CW for ovigerous females were calculated by year
following Defeo et al. (1992). Increasing or decreasing trends in mean sizes with time were tested by fitting a linear minimum squares regression to the data
and testing the slope significance against 0 (Zar,
1996).
RESULTS
Morphometric maturity
The relative growth of males showed significant
changes along the ontogeny for all selected dimen-
433
sions (p < 0.05). Transitions occurred between 8.2 and
10.6 CW (mean = 8.9 ± 0.9 SD) and several dimensions showed different relative growth patterns before
and after their transition points (Table 2, Fig. 2). Allometry in ChH was first isometric (b = 1) and then
changed to allometric positive after the respective
transition points. The allometry was also positive for
ChL in larger sizes but was preceded by an isometric
and allometric growth phase in the right and left chelae, respectively (Table 2, Fig. 2).
As observed in males, relative growth in females
was also characterized by significant changes along
the ontogeny. For both chelae, the transition points in
height and length occurred within a narrower range of
CW values (8.5 to 9.5 cm) than in the abdomen, where
growth changes were observed in comparatively
smaller sizes (7.6 cm) (Table 2, Fig. 3). In all dimensions, relative growth was first allometric positive,
changing to allometric negative for ChL (left and
right) and ChH (right) and to isometric for AW and
ChH (left) (Table 2, Fig. 3). Considering all the dimensions examined in females, the transition points of
females occurred, on average, at 8.8 ± 0.8 cm CW.
Functional/sexual maturity
The smallest male observed with copula marks was an
individual of 6.3 cm CW. A value of 0.68 was estimated for the parameter β of the logistic function, as
the proportion of males with darkened areas on their
legs never reached 100% for any size class (Fig. 4a).
The onset of sexual maturity in males (CW50%) occurred at 8.4 cm (Table 3, Fig. 4a).
The smallest female with opened vulvae measured
5.0 cm and all individuals larger than 10 cm showed
this condition, resulting in an estimate of the size of
functional maturity of 6.9 cm (CW) (Table 3, Fig. 4b).
The presence of eggs in the pleopods was first observed in a female measuring 7.0 cm CW. Based on
this characteristic, we estimated sexual maturity to
occur at 9.7 cm, and the maximum theoretical proportion of individuals carrying eggs during the main reproductive period (β parameter) was 0.8 (Table 3, Fig.
4c).
Size-structure
The global size structure of red crab catches examined
between 2001 and 2005 revealed that males were relatively larger than females, ranging from 4.9 to 17.5 cm
and 3.5 to 14.3 cm, respectively. Both sexes showed
normally distributed size frequencies, but males exhibited a fairly asymmetric distribution for smaller sizes
(Fig. 5a). The size catch-composition analysis indicated different scenarios depending on the maturity
criterion considered.
434
Table 2. Chaceon notialis. Potential regressions (Y = a Xb) fitted between carapace width (CW) (independent variable)
and abdomen width (AW), left chelae length (LChL), left chelae height (LChH), right chelae length (RChL), and right
chelae height (RChH) by sex. t-value: tests for H0: b = 1; *: p < 0.05; **: p < 0.01; D.F. degrees of freedom.
Tabla 2. Chaceon notialis. Regresiones potenciales (Y = a Xb) ajustadas entre el ancho del caparazón (CW) (variable
independiente) y ancho del abdomen (AW), largo de la quela izquierda (LChL), altura de la quela izquierda (LChH), largo
de la quela derecha (RChL) y altura de la quela derecha (RChH), por sexo. Valor de t: test para H0: b = 1; *: p < 0,05; **:
p < 0,01. DF: grados de libertad.
Sex
Male
Female
Body dimension
Transition point
(CW, cm)
AW
10.6 cm
LChL
8.7 cm
LChH
8.2 cm
RChL
8.5 cm
RChH
8.4 cm
AW
7.6 cm
LChL
8.5 cm
LChH
9.5 cm
RChL
9.4 cm
RChH
9.2 cm
Subset
a
b
r2
t-value
DF
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
Left
Right
0.2065
0.6700
0.1517
0.1813
0.1724
0.1108
0.2243
0.1720
0.2488
0.111
0.111
0.3984
0.2105
0.3524
0.1427
0.1745
0.2313
1.3287
0.1833
0.6631
1.1360
0.6562
1.2764
1.2166
1.1352
1.3857
1.1162
1.2738
0.9968
1.4200
1.6762
1.0642
1.0624
0.8328
1.2061
1.1035
1.0542
0.288
1.1180
0.5562
0.906
0.218
0.870
0.830
0.882
0.857
0.873
0.815
0.796
0.842
0.894
0.787
0.925
0.499
0.947
0.511
0.911
0.060
0.926
0.246
4.4812**
-2.9893**
3.7573**
5.4830**
1.3055
9.6353**
1.700
6.3229**
-0.0355
9.7315**
9.3888**
1.5456
2.355*
-1.9526*
10.3876**
0.3951
2.2516*
-3.3214**
5.0042**
-2.6597**
147
119
47
196
18
202
41
199
34
205
66
180
132
97
210
19
190
30
182
36
Virtually all females caught during the study period (99%) were functionally mature (Table 4). However, a radically opposed scenario emerged when considering the morphometric (i.e. mean value of the CW
transition points) and sexual maturity criteria, in
which cases the proportion of immature females in the
catches attained, on average, 67.9% and 96.7%, respectively (Table 4). Contrary to that observed in females, the contribution of immature males in the
catches was always reduced (< 12%), irrespective of
the maturity criteria chosen for analysis (Table 4).
Weighted mean sizes (CW) of ovigerous females
caught in the fishery tended to decrease along the
years of exploitation from 8.6 cm in 2001 to 8.1 cm in
2005, but this trend was not significant (b = -0.0967; p
= 0.12; t-value = -2.16) (Fig. 5b).
DISCUSSION
In this work, size at maturity estimates for C. notialis
were obtained by taking into account a scenario of
indeterminate growth, i.e. not considering the existence of a terminal molt in the species. This approach
follows the arguments of Pezzuto & Sant’Ana (2009),
which examined the maturity of the royal crab Chaceon ramosae in Brazil. The authors revealed that,
whereas some controversy does exist, at present, few
if any concrete bases can be found in the literature to
support the hypothesis of deterministic growth in
geryonids.
In a recent paper, Delgado & Defeo (2004) studied
the sexual maturity of C. notialis females in Uruguay
considering either the presence or absence of a terminal molt in the species. The estimates produced in the
present study were strikingly close to their results
(obtained under the assumption that females continue
to grow after the pubertal molt). The CW50% estimated
from females with opened vulvae were virtually identical in both studies (6.9 cm in Brazil; 7.0 in Uruguay)
and very similar to the size at maturity calculated by
Delgado & Defeo (2004) from the percentages of
females with gonads in an advanced developmental
435
Figure 2. Chaceon notialis. Plots of relative growth of chelipod and abdomen dimensions for males. Arrows indicate
Figura 2. Chaceon notialis. Relaciones de crecimiento relativo de las dimensiones de la quela y abdomen para machos.
Las flechas indican los puntos de transición entre las diferentes fases de crecimiento.
stage (7.2 cm). In addition, the CW50% estimated in
Brazil from ovigerous females (9.7 cm) matched the
mean size of females with mature gonads taken from
Uruguayan waters (~9.1 cm). The similarity among
these results reinforces the suspicion that C. notialis
may constitute a shared stock between Brazil and
Uruguay (Lima & Lima-Branco, 1991; Defeo et al.,
1992; Pezzuto et al., 2006a).
As observed in most geryonids (Hastie, 1995), C.
notialis males attain larger sizes than females (Nigge-
meyer et al., 1990). Melville-Smith (1989), who found
a similar pattern in C. maritae, argued that females
would undergo smaller size increments per molt than
males because of their higher reproductive investment.
As a consequence of the larger sizes attained by males
and their specialized copulatory behavior, which involves forming a protective cage around the receptive
female by using their locomotory legs (Elner et al.,
1987; Erdman & Blake, 1988), males also tend to
mature at larger sizes (see review in Pezzuto
436
Figure 3. Chaceon notialis. Plots of relative growth of chelipod and abdomen dimensions for females. Arrows indicate
Figura 3. Chaceon notialis. Relaciones de crecimiento relativo entre la quela y abdomen en hembras. Las flechas indican
los puntos de transición entre las diferentes fases de crecimiento.
Sant’Ana, 2009). Therefore, it is noteworthy that C.
notialis males seem to mature at relatively smaller
sizes than females, as suggested in the present paper.
In the northeast Atlantic, a similar result was found for
an exploited population of C. affinis, whose males and
females were found to mature at 94 mm and 109 mm,
respectively (Robinson, 2008). However, as expected
for the group, males of the same species mature at
larger sizes than females in the Canary Islands, where
no fishery for the species exists (Fernández-Vérgaz et
al., 2000).
Three hypotheses can be raised to explain this very
unexpected result: (i) morphological and sexual sizes
at maturity calculated in the present work for males of
C. notialis are, in fact, underestimated; (ii) female
sizes at sexual maturity (based on the proportion of
ovigerous females in the catches) are overestimated;
and (iii) all estimates are correct and a deviation does
exist in the actual population structure of the species.
The first hypothesis seems to be largely improbable as
both morphological and sexual sizes at maturity were
very similar despite being supported by completely
437
Table 3. Chaceon notialis. Parameters (α1, α2, and β) of the logistic curves (± C.I. 95%) fitted to the proportion of females with opened vulvae, ovigerous females and males showing copula marks by size class and the corresponding size at
maturity (CW50%) estimated by the bootstrap procedure.
Tabla 3. Chaceon notialis. Parámetros (α1, α2 y β) del modelo logístico (± I.C. 95%) ajustados a la proporción de hembras con vulvas abiertas, hembras ovígeras y machos con marcas de cópula por clases de talla y las correspondientes tallas
de primera madurez (CW50%), estimadas por bootstrap.
Parameters
Β
α1
α2
CW50% (cm)
Bootstrap
CW50% (cm)
Female
Opened vulvae
Mean
0.98
12.75
1.96
6.85
Median
6.85
CI (95%)
0.95-1.00
10.55-14.95
1.54-2.18
CI (2.5-97.5%)
6.53-7.13
Ovigerous
Mean
0.80
6.89
0.69
9.98
Median
9.73
distinct data, methods, and assumptions. On the other
hand, the second hypothesis could be supported by the
fact that sizes at maturity estimated from size-specific
proportions of ovigerous females in the catches might
be influenced by the catch composition, which might
vary according to the abundance of mature and immature individuals in the fishing areas and/or due to differential attractiveness of the traps and vulnerability of
females to these during the breeding phase (MelvilleSmith, 1987). However, using fishing-based data collected in the middle 1990s, Defeo & Masello (2000a)
reported a marked reduction in the mean individual
weight of males in comparison with the original sizestructure observed before the development of the
commercial fishery in Uruguay. The authors considered this finding to be a first sign of overexploitation,
especially because, this is a male-centered fishery, i.e.,
only males are retained in that country (Delgado &
Defeo, 2004). As with the change in the male size
structure, the recent tendency toward lower mean sizes
of ovigerous females and the occurrence of smaller
average females in Brazil with opened vulvae (6.8 cm)
than observed from morphological analyses (8.9 cm)
suggest that the third hypothesis could, in fact, be true.
In this case, the population would be experiencing an
adjustment in its reproductive parameters as a response to the overexploited condition of the stock.
Not all mature males exhibited copula marks on
their legs (maximum observed and predicted proportions of individuals showing this feature were 0.74 and
0.68, respectively). Pezzuto & Sant’Ana (2009) observed similar results for C. ramosae, with a slightly
lower β parameter (0.58) in the logistic function. The
authors pointed out that such a pattern might emerge
CI (95%)
0.31-1.29
4.05-9.72
0.28-1.10
CI (2.5-97.5%)
7.29-11.01
Male
Copula marks
Mean
0.68
11.79
1.41
8.36
Median
8.40
CI (95%)
0.58-0.77
4.98-18.60
0.57-2.24
CI (2.5-97.5%)
7.95-10.0
from three main situations: a) if a proportion of the
recently paired males molted before being caught; b)
if abrasion marks are not necessarily formed in 100%
of the recently paired males; and c) if not all mature
males copulate during each reproductive season. Molting in C. notialis has not been investigated yet. Therefore, we are not able to test whether the first hypothesis could be valid for this species. However, given the
low growth rates attributable to geryonid crabs and the
increasing intermolt periods expected for large individuals (Lux et al., 1982; Melville-Smith, 1989;
Arana, 2000), it seems quite improbable that nearly
30% of adult males had molted (i.e. eliminating the
respective copula marks along with their old shells)
between the last copula and being caught, as should be
the case for supporting the first hypothesis. On the
other hand, the second hypothesis seems to be highly
plausible. The proportion of males with copula marks
was not constant in the largest size classes used in the
analysis but showed a slight reduction in the 12-cm
size class. In addition, 28 males measuring between 13
and 16.5 cm CW were also sampled during the study
and did not show any copula marks on their legs.
These specimens were not included in the analysis
given their smaller sample sizes as compared to the
numbers available for the other size classes. Both facts
support the idea that the probability of developing
copula marks could be lower from some threshold size
in mature individuals of this species. In fact, a similar
pattern was reported by Melville-Smith (1987) for C.
maritae: males larger than 12 cm CW did not exhibit
any marks on their legs. In this species, damage to the
integument of large-sized males is not produced because their merus do not chafe against the female
438
carapace during the pre-copulatory embrace and mating (Melville-Smith, 1987). It is possible, therefore,
that C. notialis behave in a similar way, with most
mature males copulating in each reproductive period
but not necessarily producing copula marks. Besides
supporting said hypothesis, our results concerning the
maximum proportion of ovigerous females by size
(see below) also offer little if any support to the third
hypothesis that individual males do not tend to reproduce each year.
Figure 4. Chaceon notialis. Logistic model (solid line)
fitted to the observed proportion (points) of males showing copula marks (a) and females with opened vulva (b)
and eggs in the pleopods (c).
Figura 4. Chaceon notialis. Modelo logístico (línea
continua) ajustado a la proporción observada (puntos) de
machos con marcas de cópula (a); hembras con vulvas
abiertas (b); y huevos en los pleópodos (c).
According to the logistic model fitted to the data,
the maximum theoretical proportion of ovigerous
females by size class was 80% (β = 0.8). β values near
1 (100%) are considerably high and suggest that reproduction in this species takes place on an annual
basis, both at the populational and individual levels, as
also found for C. maritae off Namibia (MelvilleSmith, 1987). On the other hand, the same does not
occur with the royal-crab C. ramosae in Brazil, which
has been exploited between 19 and 31°S (farther north
than the C. notialis fishing grounds; see Figure 1 in
Pezzuto & Sant’Ana, 2009). Catches of ovigerous
royal-crab females are concentrated in the first semester of each year (Pezzuto et al., 2006b), but individual
males and females seem to reproduce on a bi-annual
basis only (Pezzuto & Sant’Ana, 2009). Bi-annual
cycles were suggested for other geryonids and have
been interpreted as a consequence of the food-limited
characteristic of the deep-water environment (Erdman
& Blake, 1988; Erdman et al., 1991; Pinho et al., 1998
in López-Abellán et al., 2002). In the case of C. notialis, an annual reproductive strategy would imply a
significant energetic investment that should be compensated by comparatively higher food availability. In
fact, the species occurs along subtropical/temperate
latitudes strongly influenced by highly productive
water masses including Subantarctic Water carried out
by the Malvinas Current, the Subtropical Convergence
formed between the Malvinas and Brazil currents, and
discharge from La Plata River (Garcia & Garcia,
2008). Therefore, higher biological production levels
should be expected to occur along the C. notialis distributional range than in the tropical waters under
which C. ramosae occurs (see review on primary productivity along southeastern and southern Brazil in
Gaeta & Brandini, 2006). These processes also seem
to influence the biomass of the respective stocks. Defeo et al. (1991) concluded, based on surveys conducted in the middle 1980s, that C. notialis shows one
of the highest biomasses estimated for geryonid crabs
in the world, even considering only the portion of the
stock found in Uruguay and northern Argentina.
439
Figure 5. Chaceon notialis. Size-frequency distribution of males and females (a) and variation of mean sizes of ovigerous
females (b) caught in commercial fisheries in southern Brazil between 2001 and 2005. In (b), boxes and bars are, respectively, confidence intervals (95%) and standard deviations.
Figura 5. Chaceon notialis. Distribución de frecuencia de tallas de machos y hembras (a) y variación de los tamaños
promedios de las hembras ovígeras (b) capturadas por la pesca comercial en el sur de Brasil entre 2001 y 2005. En (b) se
presentan los intervalos de confianza al 95% (cajas) y las desviaciones estándar.
Table 4. Chaceon notialis. Percentages of immature and mature individuals in the commercial catches by sex and year,
according to the different criteria for determining sexual maturity. SD: standard deviation.
Tabla 4. Chaceon notialis. Porcentaje de individuos inmaduros y maduros en las capturas comerciales por sexo y año
según los distintos criterios de determinación de la madurez sexual. SD: desviación estándar.
Females
Year
Relative growth
(8.8 cm)
Opened vulvae
(6.9 cm)
Males
Eggs in the pleopods
(9.7 cm)
Immature Mature Immature Mature Immature
(%)
(%)
(%)
(%)
(%)
Mature
(%)
Relative growth
(8.9 cm)
Copula marks
(8.4 cm)
Immature Mature Immature Mature
(%)
(%)
(%)
(%)
2001
59.9
40.1
0.0
100.0
94.9
5.1
3.4
96.6
1.2
98.9
2002
64.8
35.2
1.3
98.7
93.2
6.8
12.4
87.6
6.0
94.0
2003
67.8
32.2
0.2
99.8
98.5
1.5
8.3
91.7
2.9
97.1
2004
68.4
31.6
2.5
97.5
97.4
2.6
17.2
82.8
11.0
89.0
2005
78.4
21.6
0.8
99.3
99.6
0.4
17.7
82.3
10.3
89.7
Mean
67.9
32.1
0.9
99.1
96.7
3.3
11.8
88.2
6.3
93.7
SD
6.8
6.8
1.0
1.0
2.6
2.6
6.1
6.1
4.4
4.4
In spite of the relatively high value obtained for the
maximum theoretical proportion of ovigerous females
by size class, it must be stressed that, at present, the
observed values peaked at a much lower level (0.61).
Delgado & Defeo (2004) investigated the sexual maturity of the same species in Uruguay and observed
that 65% of the morphologically mature females
showed marks of mating. In addition, most of them
lacked seminal contents in their reservoirs. Delgado &
Defeo (2004) suggested that, due to the selective exploitation of males, the sperm supply might have become a limiting resource for the population. A similar
concern was raised by Wahle et al. (2008) for the
northwest Atlantic red crab C. quinquedens fishery,
440
where the abundance of large males declined by 42%
after three decades of selective harvesting. Our results
could support the Delgado & Defeo (2004) hypothesis, considering that most C. notialis males caught in
Brazil (supposedly in much lower numbers than in the
original population structure) have shown signs of
reproductive activity (copula marks), but a proportionally smaller portion of the females seem to have been
effectively fertilized. Examining the temporal series of
sex-ratio and ovigerous females caught by reproductive season (available at least for the Brazilian portion
of the stock) could provide more support to test this
hypothesis in the future.
Analyzing the percentages of immature crabs in the
commercial catches reveals distinct scenarios depending on the sex and maturity criteria analyzed. In Brazil, the participation of immature males in the catches,
although higher in 2004 and 2005, has been quite low.
On the contrary, most females caught in Brazil could
be classified as immature, considering both morphometric and sexual sizes at maturity. Taking into
account that a) contrary to the situation in Uruguay,
the Brazilian fishery has been predominantly sustained
by females, b) enforcement in Brazil has not been
completely successful as catches have also surpassed
the maximum estimated sustainable yield in most
years and minimum mesh sizes restrictions have not
been observed, c) mean sizes of ovigerous females
seem to be declining over the years, and d) the stock
biomass in the Brazilian EEZ was reduced by 30% in
2005 (Pezzuto et al., 2006b), the excessively high
mortality levels imposed on immature females could
contribute to a much more severe impact on the stock.
This scenario points to a biologically unsustainable
condition that should be changed by modifying and
including new measures in the management of the C.
notialis fishery in Brazil. These measures should emphasize enhancing trap selectivity (Tallack, 2007) and
the implementation of spatial and temporal restrictions
on effort allocation in order to reduce catches of immature and ovigerous females by the fleet. Based on
the results from this paper and from Pezzuto et al.
(2006b), the present management of the C. notialis
fishery in Brazil has been changed recently, incorporating, inter alia, a 30% reduction in the TAC, an
increase in the permitted minimum mesh size in the
traps (from 100 to 120 mm stretched), and the closure
of the spawning areas < 600 m depth to the fishery
from 1 August to 31 December each year. As the vessels targeting C. notialis should be obligatorily monitored by observers on 100% of their trips, biological
data will be available in order to verify the efficacy of
these changes and to refine them, if necessary, in a
continuous process of adaptive management. On the
other hand, the establishment of collaborative efforts
between Brazilian and Uruguayan fishing authorities
and scientists should be encouraged in the near future
in order to confirm the shared status of the stock and
implement global management measures intended to
ensure the biological sustainability of C. notialis.
ACKNOWLEDGEMENTS
The authors are indebted to all observers whose hard
work resulted in most of the high-quality data available for this study. The kind assistance provided by
Helia del Carmen Farias Espinoza (CTTMar/
UNIVALI) with the Spanish version of the Abstract
and captions is fully appreciated. This work was
funded by the Special Secretary of Aquaculture and
Fisheries (Brazilian Government–SEAP/PR/001/
2003, SEAP/PR/078/2004, SEAP/PR/064/2005, and
SEAP/PR/027/2007) and by a research grant to P.R.P.
from the National Research Council (CNPq) (Process
310820/2006-5). This work is part of the Bachelor
thesis in Oceanography (UNIVALI) by R.S.
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Reproduction and population structure of Aristeus antillensis
443
Research Article
Reproductive cycle and population structure of the deep-water shrimp
Aristeus antillensis A. Milne Edwards & Bouvier, 1909 (Decapoda: Aristeidae)
on southeast Brazilian continental slope
1
Paulo Ricardo Pezzuto1 & Martin Coachman Dias1
Rua Uruguai, 458, CEP 88.302-202, Itajaí, SC, Brazil
ABSTRACT. The “alistado shrimp” (Aristeus antillensis) is one of the targets of the trawling fleet operating
since 2002 along the continental slope of the Brazilian Economic Exclusive Zone between 700 and 800 m
depth. Catches of the species occur mainly in two small fishing grounds located on the east coast of Espírito
Santo State (19-22°S). This paper aimed to obtain the first biological data for this species along the Brazilian
coast. A total of 13,797 individuals were sampled aboard fishing vessels by observers on almost all fishing
hauls, corresponding to 10 to 20% of the total catch recorded in the period. Males and females are sexually
mature at 25.4 and 40.2 mm carapace length, respectively, based on an analysis of the proportions of individuals with fused petasma (males) and spermatophores in the thelycum (females). The proportion of impregnated
females was higher than 80% year round, suggesting a continuous reproductive cycle, although preliminary information on gonadal development points to possible seasonal reproduction. In general, mature females, which
attain larger sizes than males, dominate the catches (M:F = 0.12:1). However, populational groups including
males and juveniles of both sexes occupy the fishing grounds in different periods of the year, probably reflecting migratory movements whose directions and driving forces are not completely understood yet. A depthstratified population structure by sex and size is hypothesized.
Keywords: deep-water resource, sexual maturity, reproductive cycle, population structure, Aristeidae, Brazil.
Ciclo reproductivo y estructura poblacional del camarón de aguas profundas
Aristeus antillensis A. Milne Edwards & Bouvier, 1909 (Decapoda: Aristeidae)
en el talud continental del sureste de Brasil
RESUMEN. La gamba de aguas profundas Aristeus antillensis es uno de los recursos explotados por la flota
de arrastre, que está operando desde el año 2002 en el talud continental de la Zona Económica Exclusiva de
Brasil, entre 700 y 800 m de profundidad. Las capturas de esta especie se realizan básicamente en dos pequeños fondos de pesca que se encuentran en la costa este de la región de Espírito Santo (19-22°S). Este trabajo
tiene por objetivo obtener los primeros antecedentes biológicos de esta especie en la costa brasileña. Un total
de 13.797 camarones fueran muestreados en los buques pesqueros por observadores en casi todos los lances de
pesca, que correspondieron entre 10 y 20% de las capturas totales en el período. Machos y hembras están
sexualmente maduros a 25,4 y 40,2 mm respectivamente (longitud de carapazón), según el análisis de las proporciones de individuos con petasma unido (machos) y telicum con espermatóforo (hembras). La proporción
de hembras con espermatóforo fue superior a 80% en todo el año, sugiriendo un ciclo reproductivo continuo.
Sin embargo, informaciones preliminares sobre el desarrollo gonadal indican una posible estacionalidad en la
reproducción. Generalmente, hembras adultas, que alcanzan tallas mayores que los machos, dominaron las
capturas (M:F = 0,12:1). Sin embargo, grupos poblacionales, incluyendo machos e inmaduros de ambos sexos,
ocupan los fondos de pesca en diferentes períodos del año, probablemente como reflejo de los movimientos
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migratorios, cuyas direcciones y fuerzas aún no son totalmente comprendidos. Se discute una posible estructura poblacional estratificada de sexos y tallas por el gradiente batimétrico.
Palabras clave: recurso de profundidad, madurez sexual, ciclo reproductivo, estructura poblacional, Aristeidae, Brasil.
________________________
Corresponding author: Paulo Ricardo Pezzuto: ([email protected])
INTRODUCTION
Deep-water shrimps from the family Aristeidae represent an important and valuable fishery resource in
many parts of the world (Crosnier & Tauter, 1968;
Rainer, 1992; Guéguen, 1998; Kao et al., 1999;
Ragonese et al., 2002; Tudela et al., 2003; Can &
Aktas, 2005).
On the Brazilian coast, the exploitation of aristeid
shrimps started in 2002 as part of a governmental
program launched to expand industrial fisheries to
previously unexploited slope fishing grounds where
valuable benthic and demersal resources concentrate.
The history and dynamics of this fishery, which experienced a “boom and bust” developmental cycle,
have been extensively reviewed by Pezzuto et al.
(2006) and Dalagnollo et al. (2009).
Since the beginning of the fishery, Aristaeopsis
edwardsiana (“carabineiro” or scarlet shrimp), Aristaeomorpha foliacea (“moruno” or giant red shrimp),
and Aristaeus antillensis (“alistado”) have been the
targets of bottom stern-trawlers along almost all the
Brazilian Economic Exclusive Zone (EEZ), but operations have concentrated mainly between 18°S and
34°S and from 700 to 800 m (Pezzuto et al., 2006;
Dallagnolo et al., 2009). A. antillensis is the least
abundant species in the catches, representing nearly
5% of the total deep-water shrimp landings recorded
between November 2002 and May 2007. In part, this
reflects the fact that most of the exploitable biomass of
the species is largely concentrated in only two small
fishing grounds (total area = 588.3 km2) located on the
eastern coast of the Espírito Santo State (19-22°S)
(Dallagnolo, 2008; Dallagnolo et al., 2009). Scientific
surveys conducted in this area revealed otherwise, that
A. antillensis exhibits a wider bathymetric distribution
ranging between 200 and 1,144 m, with density peaks
at 750 m deep (Pezzuto et al., 2006; Serejo et al.,
2007).
In general, aristeid shrimps are believed to be more
vulnerable to overexploitation than coastal penaeids
due to: a) their higher economic value; b) K-strategist
life history, with lower growth rates and longer life
spans; c) complex distribution patterns, with migratory
movements across bathymetric gradients; and d) aggregated reproductive behavior, inducing the seasonal
formation of highly vulnerable biomass concentrations
in the fishing grounds (Ragonese & Bianchini, 1996;
Sardá et al., 2003a, 2003b; Tudela et al., 2003;
Pezzuto et al., 2006; Dallagnolo et al., 2007; Pezzuto
& Dias, 2007). Biological information about A. antillensis is very scarce. As far as we know, the only specific studies available to date were carried out by
Guéguen (2000, 2001), who described the bathymetric
distribution, morphometry, overall sex-ratio, and sizefrequency distribution of the species on the continental
slope of French Guiana, where A. antillensis is also a
minor component of a seasonal industrial fishery for
A. edwardsiana. However, despite not knowing the
growth rates, longevity, and other biological characteristics of A. antillensis, high prices in the international market, low biomass levels, and a distribution
concentrated in a few, small, easily accessible fishing
areas in southeastern Brazil make the species highly
susceptible to severe depletions in the near future.
A management plan for the aristeid fishery is now
being discussed and implemented in Brazil. This is
mostly concerned with the sustainability of A. edwardsiana, the main target of the fishery. A total allowable catch (TAC) of 60,000 kg has been set for the
three species together but, in order to protect A. antillensis from depletion, fishing operations north of 21°S
must be stopped when its annual catches reach 4,350
kg, the estimated Maximum Sustainable Yield (MSY)
for the species (Dallagnolo, 2008; Perez et al., 2009).
As biological reference points based on size/sexstructure and reproduction are not available for the
three species, this work aimed to provide the first
results on the population structure and reproductive
biology of A. antillensis in Brazilian waters in order to
support additional recommendations for the sustainable exploitation of this new deep-water resource.
Study site
Commercial catches of aristeid shrimps occur in four
fishing grounds (N1 to N4) over the continental slope
of the Espírito Santo State (Fig. 1). However, A. antil-
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Figure 1. Main fishing grounds of Aristeus antillensis (N2 and N4) in southeastern Brazil. ES, MG, and RJ refer to Espírito Santo, Minas Gerais, and Rio de Janeiro states.
Figura 1. Principales fondos de pesca del Aristeus antillensis (N2 y N4) en el sueste de Brasil. ES, MG y RJ se refieren a
los estados de Espirito Santo, Minas Gerais y Rio de Janeiro.
lensis is mostly found in only two of them: N2 and
N4. These are located in an area with very distinct
morphological and oceanographic characteristics on
the Brazilian coast. They are situated close to or inside
the Vitória Channel, a deep strait that separates the
continental slope adjacent to the Abrolhos Bank from
the scarp of the Besnard seamount, one of the main
features of the Vitória-Trindade chain (20 to 21°S)
(Fig. 1). In this area, the continental slope is very steep
and narrow (18 km), exhibiting several small subparallel canyons extending from the shelf to nearly 800 m
depth. Both canyons and the slope are supposed to
receive a terrigenous influence from the discharge of
the Rio Doce (França, 1979). Three water masses have
been found to occupy the upper 1,500 m of the water
column over the A. antillensis fishing grounds: a)
Tropical Water (TW; T > 20°C; S > 36.2) occupies the
surface layers (0 ~ 200 m) flowing towards the southwest; b) South Atlantic Central Water (SACW; T = 620°C; S = 34.6-36) is found below the TW up to 700
m depth, and c) Antarctic Intermediate Water (AIW; T
= 3-4°C; S = 34.2-34.6) flows to the north between
700 and 1,500 m (Costa et al., 2005; Castro et al.,
2006; Haimovici et al., 2007). The euphotic zone is
dominated by oligotrophic warm tropical waters having low productivity and primary productivity that is
not uniform either spatially or temporally. Lower and
higher values are found, respectively, in the summer
and winter months, whereas intermediate ones occur
in the autumn and spring. Major estuaries such as Rio
Doce, which opens to the sea in front of the N4 fishing
ground, exert a positive influence on the inner shelf,
creating areas of higher primary production. In addition, both the Abrolhos bank and Vitória-Trindade
chain act as important topographic barriers to the Brazil Current, which carries the TW along the eastern
coast of Brazil towards the south, producing a very
complex hydrographic structure including vortices,
upwellings, and vertical mixing processes (Valentin et
al., 2007). One of these features, the “Vitória vortex”,
forms south of the Abrolhos bank, enriching the euphotic zone with comparatively nutrient-rich SACW
waters (Ciotti et al., 2007; Rezende et al., 2007;
Valentin et al., 2007).
Sampling and processing
Fishing and biological data used in this work were
collected by observers aboard all commercial vessels
that operated off the Espírito Santo State (18°20’22°S, 360 to 890 m depth) between October 2003 and
November 2008 (Fig. 1). Details about the fleet and
gears can be found in Dallagnolo (2008) and Dallagnolo et al. (2009). For each trawl, the geographic coordinates, date, time, and depth (m) were recorded at
deployment and retrieval, and trawl speed (nm h-1),
trawl duration (h), head rope length (m), mesh size at
cod-end (mm), and catch composition (kg) were also
registered. A total of 13,797 individuals were sampled
from almost all the fishing hauls, corresponding to
10% to 20% of the total catch recorded in the period.
446
Only individuals caught between 650 and 800 m
depth were considered in this study, as nearly 80% of
the hauls with positive catches of the species occurred
between these limits. As significant differences in
size-sex structure with depth have been found for
other Aristeids, including the congeneric species A.
antennatus in the Mediterranean (Sardà & Cartes,
1993; Sardà et al., 2003b, 2004; Tudela et al., 2003),
this procedure intended to eliminate possible noise
caused by samples eventually taken in other depth
strata where population characteristics could differ
from those found in the main fishing grounds.
Sex was identified macroscopically in all shrimps
by the presence of petasma in males and thelycum in
females. Carapace length (CL) was measured with
sliding calipers (precision 1 mm) from the orbit to the
dorsal mid-point of the posterior margin of the carapace. Numbers in the samples were raised to the total
catch of each haul by multiplying them by the quotient
between total catch and sample weights recorded by
the observers.
Size at maturity and the reproductive cycle were
studied in an additional sample of 2,419 individuals
examined aboard between July 2005 and November
2008 during the same trips. As most of these shrimps
pertained to the medium and large size classes (i.e.
males > 27 mm, females > 40 mm CL), this sample
was added, respectively, to the 148 and 254 small
males and females caught in northeastern Brazil by the
same vessels in the same period and depths. Males
were classified according to the following criteria: a)
terminal ampullae empty (immature) or filled with
sperm (mature), and b) petasma with their lobes fused
(mature) or separated (immature). Females were examined only to identify the presence or absence of
spermatophores plugged in their telicum (Sardá &
Demestre, 1989; Belcari et al., 2003); macroscopic
examinations of the gonads were not possible aboard
due to logistical constraints. As we could not assess
whether inseminated females were, in fact, physiologically mature, our estimates of size at maturity for
A. antillensis refer only to the median size at which
females are able to copulate and retain spermatophores
in their telycum.
Data analysis
Size at maturity (CL50%) was estimated by examining
the proportion of females (n = 2,351) carrying a spermatophore and males (n = 469) with fused petasma by
size class. Because nearly 100% of the males in the
smallest size class sampled (24 mm CL) showed their
ampullae filled with sperm (i.e. were physiologically
mature), no attempt was done to calculate size at maturity (CL50%) based on this criteria, as very biased
estimates could result from modeling proportions in
size classes not represented in the samples.
A non-linear minimum squares estimation procedure was used to fit a generalized logistic model (Restrepo & Watson, 1991) to the data as follows:
PCL =
β
1 + e(α1 −α 2CL)
(1)
where PCL is the proportion of individuals in each size
class, and α1, α2, and β are parameters. In this model,
β is a more general parameter that allows for the asymptotic proportion of the model to be lower or equal
to 1. Therefore, a penalty function for β ≤ 1 was included in the parameter estimation procedure. Size at
maturity was given by the equation:
α
CL50% = 1
α2
(2)
The reproductive cycle was studied by analyzing
the monthly variation in the proportion of spermatophore-bearing females and males with terminal ampullae filled with sperm masses. Only potentially mature
individuals (i.e. with CL larger than CL50%) were considered for this analysis.
Temporal changes in the population structure of
the alistado shrimp were investigated by examining
size frequency distributions, sex ratio (M:F), and the
proportion of immature (individuals smaller than
CL50%) and mature individuals in the catches monitored between October 2003 and March 2007. Data
were analyzed both globally (i.e. considering this
whole sampling period) as well as grouped by month.
For the sake of simplicity, seasons were defined
here as summer (January to March), autumn (April to
June), winter (July to September) and spring (October
to December).
RESULTS
Size at maturity
After exhibiting some fluctuation in the smaller size
classes, the proportion of spermatophore-bearing females showed a sharp increase in individuals larger
than 39 mm (CL) and stabilized around 0.9 between
48 and 56 mm (CL). Only individuals larger than 62
mm were all inseminated (Fig. 2a). No males smaller
than 24 mm were sampled along the study period but
nearly 32% of the individuals in this size class had
fused petasma. This proportion increased steadily up
to the 28-mm size class and oscillated around 0.9 up to
the two largest size classes, where all shrimps had
fused petasma (Fig. 2b). The logistic model fitted to
the data indicated mean sizes at maturity of 40.2 (females) and 25.4 mm (males) (Table 1).
447
Figure 2. Aristeus antillensis. Logistic model (solid line) fitted to the proportions (dashed line) of a) spermatophorebearing females and b) males with fused petasma by size class, sampled in fishing grounds N2 and N4 (southeastern Brazil) between 2005 and 2008. CL: carapace length. N males = 469; N females = 2,351.
Figura 2. Aristeus antillensis. Modelos logísticos (línea continua) establecidos para las proporciones (línea descontinua)
de a) hembras cargando espermatóforo y b) machos con petasma unido en grupo de tallas, muestreados en los fondos de
pesca N2 y N4 (sudeste de Brasil) entre 2005 y 2008. CL: longitud del carapazón. N machos = 469; N hembras = 2.351.
Table 1. Aristeus antillensis. Parameters (α1, α2, β) of the logistic curves (± CI 95%) fitted to the proportion of males
with fused petasma and spermatophore-bearing females by size class and the corresponding sizes-at-maturity (CL50%).
Tabla 1. Aristeus antillensis. Parámetros (α1, α2 y β) de las curvas logísticas (± CI 95%) ajustados para las proporciones
de machos con petasma unido y hembras cargando espermatóforos por clase de talla, y las correspondientes tallas de
primera madurez (CL50%).
Males
Parameter
Females
Mean
CI (95%)
Mean
CI (95%)
β
0.922
0.870 - 0.974
0.942
0.917 - 0.968
α1
19.264
10.830 - 27.699
35.881
26.078 - 45.684
α2
0.758
0.427 - 1.089
0.892
0.648 - 1.137
CL 50% (mm)
25.4
-
40.2
-
Reproductive cycle
The percentage of spermatophore-bearing females
larger than the CL50% was higher than 80% during the
entire year except in December when no data were
available (Fig. 3a). Sexually mature males were much
scarcer than females. Therefore, the analysis of the
reproductive cycle was restricted to five months (late
autumn to early austral spring). Proportions of males
whose terminal ampullae contained sperm were very
high from June to October, ranging between 87%
(June) and 100% (October) (Fig. 3b).
Population structure
Catches of A. antillensis in the N2 and N4 fishing
grounds were dominated by females and immature
individuals of both sexes (Table 2). Females were
significantly larger than males and represented nearly
90% of the individuals sampled along the study period. The global size-frequency distribution of males
was polymodal and asymmetrical for larger sizes, with
the main mode peaking at 30 mm. The female distribution was nearly bimodal, with the highest frequencies occurring between the 44 and 50-mm size classes
(Fig. 4).
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Figure 3. Aristeus antillensis. Monthly proportion of females with spermatophores (a) and males with sperm in their
terminal ampullae (b) sampled in fishing grounds N2 and N4 (southeastern Brazil) between 2005 and 2008.
Figura 3. Aristeus antillensis. Proporción mensual de hembras portando espermatóforo (a) y machos con ampollas seminales llenas (b) muestreados en los fondos de pesca N2 y N4 (sudeste de Brasil) entre 2005 y 2008.
Table 2. Aristeus antillensis. Number of shrimps sampled and caught (estimated), sex-ratio (M:F), numbers and percentages of sexually immature males and females in fishing grounds N2 and N4 during the study period.
Tabla 2. Aristeus antillensis. Número de camarones muestreados y capturados (estimados), proporción sexual (M:F),
número y porcentajes de machos y hembras en los fondos de pesca N2 y N4 durante el período de estudio.
Number sampled
Number caught (estimated)
Immature (estimated)
Immature (%)
Males
Females
M:F
Total
1,582
12,215
-
10,662
89,751
3,026
22,749
-
25,775
28%
25%
-
-
13,797
0.12:1 100,413
Figure 4. Aristeus antillensis. Global size-frequency
distribution of males and females caught in fishing
grounds N2 and N4 (southeastern Brazil) between 2003
and 2007. Arrows indicate the CL50% of males (left) and
females (right).
Figura 4. Aristeus antillensis. Distribución global de las
frecuencias de talla de machos y hembras capturados en
los fondos de pesca N2 y N4 (sudeste de Brasil) entre
2003 y 2007. Las flechas indican el CL50% de machos
(izquierda) y hembras (derecha).
Monthly changes were observed in either the sexratio or in the percentage of immature individuals.
Females always dominated the catches, but the proportion of males increased from June to October (Fig.
5). During most of the year, immature individuals of
both sexes contributed with less than 15% of the
catches. However, their occurrence increased sharply
from late spring to mid-summer, especially for immature males, whose contribution exceeded 70% in February (Fig. 5).
Examining monthly changes in size-frequency distributions by sex revealed that the fishing grounds are
occupied by different populational groups along the
year (Fig. 6). As previously shown in Figure 5, immature individuals (males and females smaller than 25.4
and 40.2 mm CL, respectively) were present in large
numbers from December to February in conjunction
with intermediate-sized mature males and females
(~29 mm and ~45 mm CL, respectively). From April
to June, males and immature females practically disappeared and the fishing grounds were occupied
mostly by large-sized females measuring between 43
and 50 mm. Mature males (27-31 mm CL) appeared in
large numbers in the winter (July to September) and
gradually reduced their occurrence in October and
November, when mostly large-sized females remained
in the area.
Figure 5. Aristeus antillensis. Monthly variation in the
sex-ratio (M:F) and in the proportion of immature individuals of both sexes caught in fishing grounds N2 and
N4 (southeastern Brazil) between 2003 and 2007.
Figura 5. Aristeus antillensis. Variación mensual en la
proporción sexual (M:F) y en las proporciones de inmaduros de los dos sexos capturados en los fondos de pesca
N2 y N4 (sudeste de Brasil) entre 2003 y 2007.
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DISCUSSION
The present work represents the first contribution to
the knowledge of the reproductive biology and population structure of the deep-sea shrimp Aristeus antillensis in Brazil, complementing the taxonomic (Tavares & Serejo, 2007), distributional (Araújo-Silva,
2002a, 2002b; Costa et al., 2005; Serejo et al., 2007),
technological, and fishing (Asano Filho & Holanda,
2005; Pezzuto et al., 2006; Dallagnolo, 2008; Dallagnolo et al., 2009) data available on the species in Brazilian waters.
Following the general rule verified for other
aristeid species, A. antillensis exhibits strong sexual
dimorphism, with females being significantly larger
than males. Commercial catches have been shown to
be dominated by females as well.
In spite of the widespread latitudinal distribution of
the slope trawling fleet operations along the region
(Dallagnolo et al., 2009), catches of the species have
been obtained mostly in the two fishing grounds selected for this study, producing nearly 73% of the
species landings monitored by Dallagnolo (2008)
between November 2002 and May 2007. Moreover,
the species distribution was found to not be homogeneous along the bathymetric gradient; rather, the best
catch rates and yields were concentrated in a very
small depth range, declining steadily in areas deeper
than 800 m (Pezzuto et al., 2006; Serejo et al., 2007;
Dallagnolo et al., 2009). Although making only a
small contribution to the total deep-sea shrimp landings in Brazil, the concentration of the catches in such
small areas suggests a striking dependence of A. antillensis on some locally prevailing environmental conditions that are not yet totally understood.
The dominance of mature females in the commercial catches raises the hypothesis that the otter trawls
used in the fishery could be selective, retaining fewer
small-sized males and juveniles. This explanation was
also proposed by Guéguen (2001) in French Guiana,
where females of the same species accounted for 99%
of the catches obtained on four research cruises (depth
range = 200 to 900 m). However, the temporal
changes in the size-frequency distributions by sex
reveal that males and juveniles were caught in large
numbers in Brazil during some periods of the year.
Therefore, without rejecting the possible contribution
of the net cod-end selectivity to the catch-size composition, it is probable that, in fact, males and juveniles
are not totally available during part of the year. In this
case, part of the stock should move seasonally to and
from the fishing grounds. Where they can be found the
rest of the time is a question that needs to be investigated.
450
Figure 6. Aristeus antillensis. Monthly size-frequency distributions of males and females caught in fishing grounds N2
and N4 (southeastern Brazil) between 2003 and 2007. Arrows indicate CL50% of males (left) and females (right).
Figura 6. Aristeus antillensis. Distribución mensual de frecuencias de tallas de machos y hembras capturados en los fondos de pesca N2 y N4 (sudeste de Brasil) entre 2003 y 2007. Las flechas indican el CL50% de machos (izquierda) y hembras (derecha).
Migratory movements of the congeneric A. antennatus have been largely observed in the Mediterranean, especially in the vicinity of submarine canyons
(Sarda et al., 1997, 2003a, 2003b, 2004; Tudela et al.,
2003). The species shows a well described segregation
with depth: mature females concentrate in shallower
slope areas (500-900 m) and juveniles are largely
dispersed along deeper grounds (i.e. > 1,000 m). Supposedly, this pattern contributes to resource optimization, concentrating reproductive potential and recruitment in different areas (Sardà & Cartes, 1993; Sardà
et al., 2003a, 2003b). Apart from ontogenetic movements, seasonal migrations of this species have been
attributed to the need to develop reproductive aggregations and/or exploit distinct energetic and trophic conditions. More recently, the role of climate and extreme
bottom currents in the interannual displacement of the
stock to the lower slope have also been demonstrated
(Company et al., 2008).
In southeastern Brazil, A. antillensis is known to
inhabit slope grounds up to 1,144 m depth (Serejo et
al., 2007) but, unfortunately, no information on its
population structure is available outside of the fishing
grounds examined in the present study. Analyzing the
distribution, abundance, and zonation of crustaceans
collected during two research cruises conducted in the
shelf break and slope of the study area (maximum
depth 2,178 m), Serejo et al. (2007) identified three
main assemblages dispersed along different bathymetric ranges (< 500 m; 500 to 900 m; > 900 m). In spite
of being found in deeper areas, A. antillensis was one
of the main components of the intermediate group
(500-900 m), which also included the giant isopods
Bathynomus giganteus and B. miyarei, the aristeids
Aristaeomorpha foliacea and Aristaeopsis edwardsiana, the sergestid Sergia prehensilis, and the carideans
Plesionika spp., Glyphocrangron alispina, and
Janicella spinicauda (Serejo et al., 2007). Studied
concomitantly in the same area, cephalopods and bony
demersal fishes also showed quite similar trends, as
medium and lower slope assemblages of these
megafaunal groups were found to be separated by
depths situated roughly between 750 and 900 m
(Costa et al., 2007; Haimovici et al., 2007). Taking
into account the correspondence between the distributional patterns of the fish assemblages and the local
water masses, Costa et al. (2007) suggested that the
4°C isotherm (corresponding to the upper limit of
AIW) could determine the transition between the
bathyal and abyssal fauna in the study area.
Based on these findings, it is possible to hypothesize that, as observed for A. antennatus in the Mediterranean waters, males and juveniles of the species also
inhabit deeper areas in southeastern Brazil, below the
limit between SACW and the colder AIW. Childress
et al. (1990) has demonstrated experimentally that
metabolic rates of decapod crustaceans decline with
increasing depth of occurrence as a response to the
concurrent decline in temperature. In the Mediterranean, such segregation has been attributed mostly to a
451
food-resource optimization strategy since temperature
remains constant around 13°C along the slope (Sardà
& Cartes, 1993), whereas, in Brazil, water temperature
could play a more significant role: the distribution of
smaller-sized individuals (males and juveniles) in the
colder areas dominated by AIW could partially compensate the higher expected size-specific metabolic
demand.
A wind-induced subsurface intrusion of SACW
over the shelf bottoms is known to occur seasonally in
south and southeastern Brazil in the austral summer.
This water mass, whose upper levels are otherwise
restricted to the shelf break, invades the inner shelf
and enriches coastal waters with nutrients (Castro et
al., 2006). It is not clear whether the seasonal movement of SACW exerts some influence at its base, also
bringing part of the AIW to the upper levels of the
slope. However, if this occurs, then the appearance of
large numbers of males and juveniles in the catches –
as observed from December to February – could support the hypothesis that they inhabit deeper waters,
appearing in the fishing grounds during seasonal
movements of the water masses.
Whether A. antillensis shows a continuous or seasonal reproductive cycle is a question that needs to be
investigated. Sexually mature males and large-sized
females were observed simultaneously in the fishing
grounds during austral winter when the sex-ratio
(M:F) also increased, indicating that reproduction
could occur mostly between July and September.
However, as the proportion of impregnated females
remained very high year round, a continuous reproductive cycle is also suspected. A definitive answer to
this question depends on obtaining temporal series of
macro- and microscopic gonadal development data.
Although this was not possible for this study, an exploratory analysis was conducted based on a small
subsample of 58 large-sized females (i.e. CL > CL50%)
of A. antillensis caught in January, April, May, June,
July, October, and December. Animals were selected
aboard by the observers, frozen, and brought to the
laboratory for processing. Gonads were examined
macroscopically and classified in four stages (I undeveloped; II developing; III mature; IV spawning),
taking into consideration the progressive increase in
size and change in color verified along their development. From preliminary observations, the color scale
used by Orsi-Relini & Relini (1998) and Kapiris &
Thessalou-Legaki (2009) for A. antennatus (white,
pink, light violet, dark violet) seemed to fit A. antillensis as well. All individuals sampled in the present
study exhibited ovaries in stages I and II and 75% of
them were impregnated, suggesting that, despite carrying spermatophores during the entire year, spawning
452
could take place in a more limited spatial-temporal
scale. Spermatophore-bearing females with immature
gonads have also been observed in other aristeids,
indicating that copula and gonadal development could
take place in different periods of the year (Papaconstantinou & Kapiris, 2003; Politou et al., 2004;
Kapiris & Thessalou-Legaki, 2009). In addition, based
on the presence of spermatophores and mature ovaries
in females of a virginal stock of A. antennatus, Kapiris
& Thessalou-Legaki (2009) estimated sizes at maturity of 26.3 and 29.4 mm, respectively, indicating that
gonadal maturity follows insemination in this species.
Fishing for A. antillensis in southeastern Brazil relies mainly on large-sized individuals that seem to be
mature. However, the spatially restricted distribution
of the species, the significant contribution of juveniles
in the summer catches, and the uncertainty about the
actual size at sexual maturity of females cannot be
disregarded for management purposes. Migratory
movements from and to the fishing grounds seem to
be the rule for the species, but neither the migratory
directions nor the driving factors are completely understood. The existence of unavailable portions of the
stock in deeper areas has been regarded as one of the
main reasons for the sustainability of the A. antennatus fishery in Mediterranean waters (Sardà et al.,
2003b). Since more definitive data are not available on
size at sexual maturity of females, the reproductive
cycle, and the distribution of the stock in different
areas and depths, a precautionary approach should be
developed for the management of the A. antillensis
fishery in southeastern Brazil.
ACKNOWLEDGEMENTS
The authors are indebted to all observers whose hard
work has made available most of the high-quality data
used in this study. This paper is part of the Bachelor
thesis in Oceanography (UNIVALI) by M.C.D. and
was funded by the Special Secretary of Aquaculture
and Fisheries (Brazilian Government–SEAP/PR/
001/2003; SEAP/PR/078/2004; SEAP/PR/064/2005;
SEAP/PR/027/2007) and by research grants from the
National Research Council (CNPq) to P.R.P. (Process
310820/2006-5) and to M.C.D. (PIBIC/CNPq/UNIVALI – 2007/2008 and 2008/2009).
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Aspectos biológicos de Coryphaenoides delsolari en Perú
455
Research Article
Aspectos de la biología de Coryphaenoides delsolari Chirichigno & Iwamoto, 1977
frente a la zona norte del Perú
Jacqueline Palacios1, Edward Barriga1, Carlos Salazar1, Aldo Rodríguez1 & Miguel Romero1
1
Instituto del Mar del Perú, Esquina Gamarra y General Valle s/n, Chucuito, Callao, Perú
RESUMEN. Para determinar la abundancia, distribución y estructura poblacional de Coryphaenoides delsolari frente a la zona norte de Perú, se analizaron los resultados de dos cruceros de evaluación realizados durante
los años 2007 y 2008, mediante la aplicación del método de área barrida con red de arrastre de fondo. Se evaluó el área comprendida entre Puerto Pizarro (3º25’S) y Huarmey (10ºS), dividida en cuatro sectores y tres niveles de profundidad entre 200 y 1500 m. C. delsolari fue el pez más representativo de las capturas realizadas
entre 500 y 1000 m más al norte de Pimentel (7ºS). La mayor abundancia fue de 3.178 kg km-2 y la biomasa
total estimada fue de 9.669,45 ton (± 4.630,15 ton). La estructura de tallas mostró una estratificación latitudinal y los ejemplares de mayor tamaño se capturaron en latitudes menores. Las hembras fueron de mayor tamaño que los machos. La relación talla-peso fue de tipo alométrico negativo.
Palabras clave: Coryphaenoides delsolari, biología, biomasa, distribución, granadero, zona norte, Perú.
Aspects of the biology of Coryphaenoides delsolari Chirichigno & Iwamoto, 1977
off northern Perú
ABSTRACT. In order to determine the abundance, distribution, and population structure of Coryphaenoides
delsolari off the northern Perú, the results of two cruises carried out in 2007 and 2008 were analyzed. For this,
the swept area method was implemented using bottom trawling from Puerto Pizarro (3°25’S) to Huarmey
(10°S). The study area was divided into three levels between 200 and 1500 m depth. C. delsolari was the most
representative fish in catches between 500 and 1000 m depth to the north of Pimentel (7°S). The highest relative abundance was 3,178 kg km-2 and the total biomass was estimated to be 9,669.45 ton (± 4,630.15 ton).
The size structure was stratified latitudinally: the lower the latitude, the bigger the fishes. Females were larger
than males. Finally, length-weight relationship was found to be negative and allometric.
Keywords: Coryphaenoides delsolari, biology, biomass, distribution, grenadier, northern Perú.
________________________
Corresponding author: Jacqueline Palacios ([email protected])
INTRODUCCIÓN
Las investigaciones sobre los macrúridos, comenzaron
durante la segunda mitad de los 1700s, cuando Gunnerus (1765) describió al roundnose grenadier Coryphaenoides rupestris. Desde entonces alrededor de 300
especies de la familia Macrouridae han sido identificadas en los océanos del mundo, de éstos más del 90%
ocupan el talud continental a profundidades de 200 a
2000 m (Atkinson, 1995).
El conocimiento de la biología de los macrúridos o
“granaderos”, en aguas peruanas es aún limitado, a
diferencia de los del Atlántico, que por su importancia
comercial han sido mejor estudiados (Bergstad, 1990).
Los granaderos son peces de profundidad, casi todos
de hábitos bentopelágicos que se distribuyen principalmente sobre la parte alta del talud continental, entre
250 y 2000 m; pocas especies han sido capturadas a
más de 5000 m. La familia Macrouridae es de distribución cosmopolita, excepto en latitudes altas del
456
Ártico y el mayor número de especies se encuentra en
aguas tropicales (FAO, 2004). Coryphaenoides delsolari se distribuye desde Colombia (Isla del Coco, 8°N)
hasta Chile (32°S) (Chirichigno & Vélez, 1998) y
habita el talud continental del mar peruano principalmente entre 250 y 2000 m (Fisher et al., 1995), condiciones batimétricas muy similares en las que habita el
Coryphaenoides rupestris del Atlántico (Bergstad,
1990).
Las campañas de investigación a bordo del buque
español B/O Miguel Oliver durante los años 2007 y
2008, se realizaron en el marco de un convenio de
cooperación entre el Instituto del Mar del Perú y la
Subsecretaria General del Mar y Asuntos Marítimos
de España, cuyo principal objetivo fue estudiar la
distribución, concentración y características biológicas
de la fauna del subsistema bentodemersal, recursos
potenciales y su relación con las condiciones del ambiente marino, en la región batial y zona arquibentónica del área marina comprendida entre Puerto Pizarro
(03º30’S) y Huarmey (10°S), en la zona norte de Perú.
Los resultados de estas campañas resaltaron la presencia de Coryphaenoides delsolari como una de las especies de peces más importantes en el talud continental del área estudiada.
En Perú, son escasos los estudios sobre las características biológicas y poblacionales de C. delsolari, por
lo que los resultados de este estudio contribuirán a
mejorar el conocimiento de esta especie y favorecer el
establecimiento de las bases científicas ante la eventualidad del desarrollo de pesquerías de profundidad
sobre esta u otras especies que comparten su hábitat.
La obtención de muestras de Coryphaenoides delsolari, se realizó a bordo del B/O Miguel Oliver, durante
dos campañas de investigación, la primera entre Puerto Pizarro (3°25’S) y Pimentel (7°S) en septiembre del
2007 y la segunda entre Pimentel (7°S) y Huarmey
(10°S) en septiembre del 2008. La evaluación de la
distribución, abundancia y estructura de la fauna batial
y arquibentónica se realizó con la aplicación del método de área barrida con redes de arrastre de fondo
(Alverson & Pereyra, 1969; Espino & WosnitzaMendo, 1984; Sparre & Venema, 1995). El área total
fue dividida en tres estratos de profundidad: 1) 200500 m, 2) 500-1000 m y 3) 1000-1500 m (Fig. 1), a las
cuales se les asignó unidades básicas de muestreo
(UBM) de 9 mn2 (3 mn x 3 mn), y donde se seleccionó
aleatoriamente un número determinando de lances,
proporcionalmente fijados de acuerdo a la extensión
total de cada estrato. Asimismo, con fines analíticos y
comparativos, el área total evaluada se dividió en cua-
Figura 1. Ubicación de los lances de pesca de arrastre
por estrato durante dos campañas de investigación (2007
y 2008).
Figure 1. Location of the trawl fishing hauls by stratum
during two research cruises (2007 and 2008).
tro sectores de acuerdo a la latitud: sector A: 3º30’5º00’; sector B: 5º00’-7º00’; sector C: 7º00’-8º30’ y
sector D: 8º30’-10º00’S.
En cada UBM seleccionada se realizaron los lances
de pesca con una red de arrastre de fondo tipo Lofoten
con nomenclatura por diseño de 456x140 de polietileno para fondos duros. Este arte con clasificación FAO
pertenece al grupo de redes de arrastre de fondo con
puertas, con tamaño de malla en el copo de 35 mm,
operado por popa del buque (OTB-2 Código ISSCFG
03.1.2), a una velocidad promedio de 3 nudos, durante
30 min de arrastre efectivo. En cada lance se anotaron
las características operacionales de la red para determinar la unidad de esfuerzo (área barrida). En cada
lance de pesca, se anotó la posición de calado, hora
efectiva de arrastre, profundidad de arrastre y composición faunística de las capturas. Asimismo, se obtuvieron muestras para determinar la estructura de tallas,
proporción sexual, relación talla-peso y madurez gonadal.
Como índice de densidad se empleó la captura por
unidad de área (CPUA), expresada en kg km-2, que es
la captura de la especie objetivo en el lance i por el
área barrida en el mismo lance:
CPUAi =
Ci
Abi
Para el cálculo de la CPUA promedio por estrato
( CPUA e ) se consideró la media aritmética de las
CPUA de todos los lances efectuados en el estrato (n):
CPUA e =
∑ CPUAi
n
La biomasa vulnerable (Be) presente en una unidad
espacial (estrato) fue determinada por el estimador de
la captura por unidad de área ( CPUA e ), amplificado o
expandido al área total (Ae) de la región o conglomerado (estrato), de acuerdo a la siguiente expresión:
Be = CPUA e ⋅ A e
Mientras que, la biomasa total (Bt) es la sumatoria
de las biomasas estimadas en todos los estratos (Be).
e
Bt =
∑
Be
1
La estructura de tallas se obtuvo mediante la distribución de frecuencias de las mediciones realizadas a
cada individuo, la talla empleada fue la longitud preanal (LPA) agrupada cada 0,5 cm y en cada caso, se
calculó la talla media y moda. Durante las capturas,
frecuentemente se encontró la mayoría de los ejemplares con la “cola” (parte delgada y larga de la zona
posterior del cuerpo) destruida total o parcialmente;
por lo que fue necesario trabajar con la longitud preanal (LPA), medida que tiene consistencia en la representación de la longitud total del cuerpo (Lorance &
Garren, 2003). La proporción sexual se estableció de
acuerdo al porcentaje de hembras. Para la relación
longitud-peso se utilizó la función potencial, cuyos
parámetros se obtuvieron del ajuste de mínimos cuadrados, previa linealización de la función mediante
logaritmo natural (ln).
La clasificación por estados de madurez gonadal,
se hizo mediante la escala empírica de Johansen
(1924), agrupando los individuos en inmaduros (estados I y II), maduros (estados III, IV y V), desovantes
(estado VI) y postdesovantes (VII y VIII).
RESULTADOS
457
captura total de 48.055,57 kg. De este total, el 92%
correspondió a 147 especies de peces, el 4,2% a 68
especies de crustáceos, 1,3 % a 34 especies de equinodermos, 1,1% a 35 especies de moluscos y el 1,7%
restante a 33 especies de otros grupos taxonómicos
(poliquetos, cnidarios, entre otros.)
Del total de lances realizados durante las dos campañas de investigación, Coryphaenoides delsolari
estuvo presente en el 85% de los lances efectuados en
el estrato 2 de profundidad (500-1000 m), en el 25,6%
de los lances efectuados en el estrato 3 (1000-1500
m), y ausente en el estrato 1 (200-500 m) (Tabla 1) y
se capturaron 3.454,9 kg en toda el área de estudio.
Distribución, densidad y biomasa
La distribución de C. delsolari abarcó entre 500 y
1600 m de profundidad, con mayor concentración
entre los 4° y 7°S, a profundidades entre 600 y 1000 m
(Fig. 2). Los mayores registros de abundancia relativa
se obtuvieron en la zona norte del área de estudio.
La mayor abundancia se presentó en el estrato 2 de
los sectores A y B, con valores medios de 1.634,72 kg
km-2 y 3.178,52 kg km-2 respectivamente; mientras
que en los sectores C y D se observó menor abundancia, con valores de 200,53 kg km-2 y 98,23 kg km-2
(Tabla 2). La biomasa total estimada por el método de
área barrida fue de 9.669,45 ton (± 4.630,15 ton) y el
56% se registró en el sector B.
Estructura de tallas
La estructura de tallas obtenida de la medición de la
longitud preanal (LPA) de 3.016 ejemplares, estuvo en
el rango entre 1,5 y 21,5 cm de LPA, con seis grupos
modales claramente distinguibles en 4, 8, 12, 15, 17 y
20 cm de LPA. De los cuales el grupo 3 (12 cm) fue el
más abundante (50% del total de la población) y se
obtuvo en los sectores A y B (Fig. 3).
C. delsolari presentó estratificación latitudinal de
tallas, observándose los de mayor tamaño en el norte y
los más pequeños en el sur. En este contexto, los sectores A y B son los que tuvieron menor o escasa presencia de los grupos modales de 4 y 8 cm de LPA, a
diferencia de los sectores C y D donde se observó la
presencia de la mayoría de los grupos modales (6),
con mayor representación de los tres primeros grupos
modales (4, 8 y 12 cm de LPA), que constituyeron el
89% de la población total (Fig. 3).
Capturas y estructura de la fauna
Estructura por sexos
Durante las campañas de investigación realizadas el
2007 y 2008 se efectuaron 122 lances de pesca cubriendo todos los sectores y estratos del área de
estudio (Fig. 1), a partir de los cuales se obtuvo una
El dimorfismo sexual se manifestó claramente al realizar el análisis de talla por sexo y se obtuvo que las
hembras alcanzaron los mayores tamaños, con una
media de 15,2 cm de LPA con predominio de los gru-
458
Tabla 1. Porcentaje de incidencia de Coryphaenoides delsolari en los lances de pesca durante dos campañas de investigación (2007 y 2008).
Table 1. Percentage of incidence de Coryphaenoides delsolari of fishing hauls during two research cruises (2007 and
2008).
Sector
A
3º30’-5º00’S
B
5º00’-7º00’S
C
7º00’-8º30’S
D
8º30’-10º00’S
Total
1 (200-500)
-
-
-
-
-
2 (500-1000)
77,8
100,0
83,3
80,0
85,0
3 (1000-1500)
42,9
45,5
16,7
25,6
Total
34,5
51,9
31,3
34,4
Estrato de profundidad (m)
25,0
Figura 2. Variación latitudinal y batimétrica de la distribución y abundancia relativa (log CPUA+1) de Coryphaenoides
delsolari en el área de estudio (el tamaño de las burbujas es proporcional a la abundancia relativa).
Figure 2. Latitudinal and bathymetric variations of distribution and relative abundance (log CPUA+1) of Coryphaenoides
delsolari in the study area (bubble size is proportional to relative abundance).
pos modales de tamaños mayores (15, 17 y 20 LPA), a
diferencia de los machos que tuvieron una media en
11,4 cm de LPA, con predominio de los grupos modales más pequeños (4, 8 y 12 LPA) en los sectores C y
D (Fig. 4).
Asimismo, la proporción de hembras confirmó lo
mencionado anteriormente (las hembras alcanzaron
mayor tamaño), los machos predominaron en tallas
menores de 13 cm de LPA, con proporción promedio
de 2 machos por 1 hembra, luego de esta talla el número de hembras se revierte, y a partir de 15,5 cm de
LPA el dominio de las hembras fue de 100% (Fig. 5).
Relación talla-peso
La relación talla (longitud preanal, cm) - peso corporal
(g) fue de tipo alométrico negativo para cada uno de
los sexos y para ambos sexos juntos (Tabla 3), con una
alta correlación entre ambos sexos (Fig. 6).
Madurez gonadal
El 92% de los individuos analizados fueron adultos
(maduros, desovantes y postdesovantes). Apenas el
8% correspondió a juveniles que fueron de menor
tamaño y se capturaron principalmente en los sectores
C y D (Fig. 7).
459
Tabla 2. Captura por unidad de área (kg km-2) y biomasa de Coryphaenoides delsolari por sector y estrato.
Table 2. Catch per unit of area (kg km-2) and biomass of Coryphaenoides delsolari by sector and stratum.
Sector
A
Estrato
B
C
1
2
3
1
2
CPUA (kg km )
0,00
1634,72
1081,57
0,00
3178,52
188,50
Desviación estándar
0,00
2955,52
2797,80
0,00
3485,83
508,90
Biomasa kg
0
2318031
1192320
0
5042939
357422
Biomasa ton
0,0
2318,0
1192,3
0,0
5042,9
357,42
-2
3
1
3
0,00
200,53
0,00
0,00
98,23
1,61
0,00
271,08
0,00
0,00
130,35
3,33
0
546494
0
0
208898
3347
0,0
546,5
0,0
0,0
208,9
3,3
Sector
A
B
C
D
3510,35
5400,36
546,49
212,25
9669,45
IC (±t)
3197,74
3322,12
388,56
158,91
4630,15
CV %
46,5
31,4
36,3
38,2
24,4
Actualmente, la mayoría de los recursos pesqueros
marinos en el mundo, se encuentra en estado de plena
y sobreexplotación; por lo tanto, la búsqueda de recursos inexplotados o subexplotados adquiere cada vez
mayor relevancia. El Perú no es ajeno a esta realidad y
existe la necesidad de identificar especies con potencial pesquero, que permitan satisfacer la demanda
pesquera nacional e internacional, crear oportunidades
de trabajo, estimular la inversión pesquera y proveer
pesquerías alternativas frente al decrecimiento de las
pesquerías tradicionales (Kameya et al., 2006). Asimismo, se tiene conocimiento de la importancia de
algunos macrúridos (e.g. Coryphaenoides rupestris)
como fuente de alimento humano y en particular por
su contenido de grasa (Atkinson, 1995), por lo que C.
delsolari puede constituir una especie potencial ante la
demanda por la búsqueda de nuevas fuentes alimenticias.
Asimismo, en el análisis de la longitud por sexo, se
observó que al igual que el Coryphaenoides rupestris
y Nezumia aequalis, las hembras de C. delsolari comparadas con los machos crecen más rápidamente, es
decir existe un dimorfismo sexual que es característica
similar para los macrúridos en general, de acuerdo con
lo reportado por Bergstad (1990) y Coggan et al.
(1999).
El comportamiento de la relación talla-peso, es similar a la del C. rupestris. Savvatimsky & Atkinson
(1993), comparan esta variable por sexos para dos
áreas de manejo, sin encontrar grandes diferencias.
1
2
3
Total
Biomasa (ton)
DISCUSIÓN
D
2
Los aportes al conocimiento de la biología de esta
especie en Perú son escasos. Mayores aportes se han
realizado en el conocimiento de macrúridos del Atlántico, destacando las diferencias tanto en estructura por
tallas o grupos modales por sexos, los cuales también
se confirman en este estudio.
Kameya et al. (2006), han identificado para las zonas batial y arquibentónica 247 especies de peces y
284 de invertebrados, con mayor diversidad entre 500
y 1000 m de profundidad, zona donde se obtuvieron
las mayores densidades de C. delsolari. En este sentido, de establecerse una pesquería, se deberá tener en
cuenta las perturbaciones que podrían ocurrir sobre la
estructura del ecosistema debido al alto descarte (bycatch) que tienen los artes de pesca poco selectivos
como las redes de arrastre.
A nivel mundial el desarrollo de la pesca de aguas
profundas ha sido, en muchos casos, más rápido que la
adquisición de los conocimientos necesarios para administrar satisfactoriamente los recursos. Los conocimientos sobre la biología de la población de muchas
especies siguen siendo insuficientes y dado el carácter
difuso de estas pesquerías, existe escasa información
sobre los efectos de la pesca en las especies capturadas
incidentalmente. En relación con los efectos sobre el
bentos, la información obtenida de los escasos estudios realizados constituye motivo de preocupación,
como en el caso de los corales de aguas profundas.
Esto pone de relieve la necesidad de que los responsables de la administración de los recursos, donde los
haya y tengan el mandato y la capacidad de hacerlo,
consideren específicamente las repercusiones de una
información científica insuficiente, de la falta o esca-
460
10
TOTAL
N = 11026
L . Media = 12.5 cm
Rango = 1.5 - 21.5 cm
Frecuencia relativa
8
6
4
2
21.5
20.5
19.5
18.5
17.5
16.5
15.5
14.5
13.5
12.5
9.5
11.5
10.5
8.5
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0
Longitud preanal
12
N = 3461
L . Media = 14.2 cm
Rango = 6.0 - 20.0 cm
SECTOR A
10
Frecuencia relativa
8
6
4
2
Figura 4. Estructura de tallas por sexos de Coryphaenoides delsolari durante dos campañas de investigación
(2007 y 2008)
Figura 4. Size composition by sex de Coryphaenoides
delsolari during two research cruises (2007 and 2008).
21.5
20.5
19.5
18.5
17.5
16.5
15.5
14.5
13.5
12.5
11.5
10.5
9.5
8.5
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0
Longitud preanal
14
N = 5617
L . Media = 13.2 cm
Rango = 4.5 - 21.5 cm
SECTOR B
12
Frecuencia relativa
10
8
6
4
2
21.5
20.5
19.5
18.5
17.5
16.5
15.5
14.5
13.5
12.5
11.5
10.5
9.5
8.5
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0
Longitud preanal
10
N = 702
L . Media = 9.9 cm
Rango = 2 - 21.5 cm
SECTOR C
Frecuencia relativa
8
Figura 5. Proporción de hembras por rango de tallas de
Coryphaenoides delsolari durante dos campañas de investigación (2007 y 2008).
Figure 5. Females sex ratio by range size of Coryphaenoides delsolari during two research cruises (2007
and 2008).
6
4
2
21.5
20.5
19.5
18.5
17.5
16.5
15.5
14.5
13.5
12.5
11.5
10.5
9.5
8.5
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0
Longitud preanal
16
14
N = 1246
L . Media = 5.8 cm
Rango = 1.5 - 21.5 cm
SECTOR D
Frecuencia relativa
12
10
8
6
4
2
21.5
20.5
19.5
18.5
17.5
16.5
15.5
14.5
13.5
12.5
11.5
10.5
9.5
8.5
7.5
6.5
5.5
4.5
3.5
2.5
1.5
0
Longitud preanal
Figura 3. Estructura de tallas total y por sectores de
Coryphaenoides delsolari durante dos campañas de investigación (2007 y 2008).
Figure 3. Size composition (total and by sector) of
Coryphaenoides delsolari during two research cruises
(2007 and 2008).
sez de datos sobre captura y esfuerzo, sobre capturas
incidentales y el desconocimiento de las trayectorias
pasadas del desarrollo de las pesquerías de aguas profundas. Lo que se sabe es que la productividad de
varias de estas pesquerías será baja, en parte como
consecuencia de la falta de alimento en hábitats de
aguas medias y profundas. Para que tengan un significado operativo algunos paradigmas o el “enfoque de
ecosistemas” en la ordenación de las pesquerías de
aguas profundas, será necesario tener en cuenta explícitamente la conservación de la biodiversidad bentónica y mantener biomasas reproductoras mínimas de las
poblaciones de peces que podrían ser pequeñas y estar
sometidas a un aislamiento reproductivo (Fischer et
al., 1995).
461
Tabla 3. Parámetros de la relación longitud-peso de
Coryphaenoides delsolari por sexo y total, en el área de
estudio (2007 y 2008).
Table 3. Length-weight relationship parameters of Coryphaenoides delsolari by sex and total, in the study area
(2007 and 2008).
Parámetro
Total
Hembras
Machos
a
0,1752
0,2152
0,1725
b
2,8848
2,8014
2,8974
r
0,9772
0,9595
0,9381
n
1246
540
259
Figura 7. Madurez gonadal de hembras de Coryphaenoides delsolari por sector en toda el área evaluada durante dos campañas de investigación (2007 y 2008).
Figure 7. Gonadal maturity of females of Coryphaenoides delsolari by sector throughout the assessed
area during two research cruises (2007 and 2008).
AGRADECIMIENTOS
Los autores expresan su agradecimiento a la Secretaría
General del Mar de España y al Instituto del Mar del
Perú, por el acceso a la valiosa información de las
campañas de investigación realizadas durante el 2007
y 2008; así como al grupo científico peruano y español
que participó en los muestreos y análisis de datos a
bordo del B/O Miguel Oliver.
REFERENCIAS
Figura 6. Relación longitud-peso de Coryphaenoides
delsolari por sexo y ajuste de la curva de poder, en toda
el área evaluada. a) total, b) hembras, c) machos.
Figure 6. Length-weight relationship of Coryphaenoides
delsolari by sex, in the assessed area. a) total, b) females,
c) males.
Atkinson D.B. 1995. The biology and fishery of roundnose grenadier (Coryphaenoides rupestris Gunnerus,
1765) in the northwest Atlantic. In: A.G. Hopper
(ed.). Deep-water fisheries of the north Atlantic oceanic slope. Kluwer, Netherlands, pp. 51-111.
Alverson, D. & W. Pereyra. 1969. A study of demersal
fishes and fisheries of the northeastern Pacific Ocean.
An evaluation of exploratory fishing methods and
analytical approaches to stock size and yield forecast.
J. Fish. Res. Bd. Can., 26: 1985-2001.
Bergstad, O.A. 1990. Distribution, population structure,
growth and reproduction of the roundnose grenadier
Coryphaenoides rupestris (Pisces: Macrouridae) in
the deep waters of the Skagerrak. Mar. Biol., 107: 2539.
Chirichigno, N. & J. Velez. 1998. Clave para identificar
los peces marinos del Perú. Publicación Especial. Instituto del Mar del Perú, Lima, 496 pp.
462
Coggan, R.A., J.D. Gordon & N.R. Merrett. 1999. Aspects of the biology of Nezumia aequalis from the
continental slope west of the British Isles. J. Fish
Biol., 54: 152-170.
Espino, M. & C. Wosnitza-Mendo. 1984. Manuales de
evaluación de Peces Nº 1. Área Barrida. Informes
Instituto del Mar de Perú, Lima, 86: 1-31.
Organización de las Naciones Unidas para la Agricultura
y la Alimentación (FAO). 2004. El estado mundial de
la pesca y de la acuicultura. Parte 2. Temas de interés
para los pescadores y acuicultores. Buena gestión y
ordenación de las pesquerías de aguas profundas. pp.
99-109.
Fischer, W., F. Krupp, W. Schneider, C. Sommer, K.E.
Carpenter & V.H. Niem. 1995. Guía FAO para la
identificación de especies para los fines de la pesca.
Pacífico centro-oriental Vol. 3 Vertebrados–Parte 2.
Roma, FAO, 3: 1201-1813.
Received: 29 May 2009; Accepted: 11 September 2009
Kameya, A., M. Romero & S. Zacarias. 2006. The deep
ocean biodiversity of the Peruvian sea: fishes and invertebrates–Peruvian activities. Deep-sea 2003: Conference on the Governance and Management of
Deep-sea Fisheries. Part 2: Conference poster papers
and workshop papers. FAO Fisheries Proceedings.
Rome, FAO, 2/3: 42-43.
Lorance, P. & F. Garren. 2003. Age estimation of roundnose grenadier (Coryphaenoides rupestris), effects of
uncertainties on ages. J. Northw. Atl. Fish. Sci., 31:
387-399.
Savvatimsky, P.I. & D.B. Atkinson. 1993. Length-weight
relationships of roundnose grenadier (Coryphaenoides rupestris Gunn.) in different areas of the
northwest Atlantic. Sci. Council Studies, 19: 71-78.
Sparre P. & S.C. Venema. 1995. Introducción a la evaluación de recursos pesqueros tropicales. Parte 1.
Manual FAO. Fish. Tech. Paper Nº306.1, Rev. 2,
Roma, 420 pp.
Lat. Am. J. Aquat. Res., 37(3): 463-478,
2009
Pesca de
Beryx splendens en montañas submarinas de Juan Fernández, Chile
463
Research Article
Rendimientos, estructuras de tallas y madurez sexual del alfonsino
(Beryx splendens) capturado en el cordón submarino de Juan Fernández, Chile
1
Casilla 1020, Valparaíso, Chile
RESUMEN. Se analiza la información recopilada en lances comerciales para la captura de alfonsino (Beryx
splendens) realizados en montes submarinos del archipiélago de Juan Fernández (Chile), entre los años 2001 y
2003, que corresponden a la etapa de desarrollo inicial de esta pesquería. En dicho período se efectuaron 187
lances, de los cuales en 121 se obtuvo la especie objetivo, capturándose 525,1 ton, que constituyeron el 99,2%
de la captura total. Por la configuración irregular de los fondos, los lances de pesca se caracterizaron por su
corta duración (0,26-0,50 h), a profundidad media de 469,7 m. En este periodo se analizaron 14.773 ejemplares, 6.064 machos (41%) y 8.709 hembras (59%), evidenciando un predominio de hembras. La proporción
sexual estructurada a la talla mostró un predominio de machos a tallas inferiores a 24 cm de longitud de horquilla (LH). En machos el tamaño medio fluctuó entre 34,6 y 36,8 cm de LH y en hembras entre 36,2 y 38,4
cm LH. Para determinar la madurez de las gónadas, se utilizó la escala macroscópica propuesta por Lehodey et
al. (1997) y se estableció que los machos alcanzaron la primera madurez (TMS50%) a 34,3 cm LH y las hembras a los 33,3 cm LH. Los rendimientos promedio en el período analizado correspondieron entre 0,2 y 6,6 ton
lance-1 y entre 1,8 y 19,0 ton h.a.-1, con medias de 4,3 ton lance-1 y 9,2 ton h.a.-1.
Palabras clave: rendimientos, estructura de tallas, madurez, alfonsino, Beryx splendens, archipiélago de Juan
Fernández, Chile.
Fishing yields, size structures, and sexual maturity of alfonsino
(Beryx splendens) caught on Juan Fernandez seamounts, Chile
ABSTRACT. We analyzed information collected during commercial hauls targeting alfonsino (Beryx splendens) on seamounts of the Juan Fernández Archipelago (Chile) from the early stages of the fishery (20012003). Of the 187 hauls carried out in this period, 121 were successful; alfonsino catches reached 525.1 ton,
constituting 99.2% of the total catch. Due to the irregularity of the sea bottom, short (0.26-0.50 h) fishing
hauls were performed at mid-depth (469.7 m). We analyzed 14,773 specimens during the study period: 6,064
males (41%) and 8,709 females (59%), the latter being predominant. The size structure was dominated by
males smaller than 24 cm fork length (LH). Average sizes fluctuated between 34.6 and 36.8 cm LH for males
and between 36.2 and 38.4 cm LH for females. To determine gonad maturity, we used the macroscopic scale
proposed by Lehodey et al. (1997); the males reached first maturity (TMS50%) at 34.3 cm LH and the females
at 33.3 cm LH. The average yields for the study period ranged from 0.2 to 6.6 ton haul-1 and between 1.8 and
19.0 ton h.a.-1, with averages of 4.3 ton haul-1 and 9.2 ton h.a.-1.
Keywords: yields, size structure, maturity, alfonsino, Beryx splendens, Juan Fernandez Archipelago, Chile.
________________________
464
INTRODUCCION
El alfonsino (Beryx splendens) es una especie de amplia distribución geográfica que vive en el talud continental y montes submarinos, tanto en aguas tropicales
como subtropicales y en algunas áreas templadas (Busakhin, 1982). Se distribuye ampliamente en diversos
océanos del mundo, excluyendo el Pacífico noreste y
mar Mediterráneo (Paxton, 1999). En el Atlántico
occidental se encuentra desde el golfo de Maine hasta
el golfo de México (Maul, 1986), mientras que en el
Atlántico oriental, desde el suroeste de Europa y las
islas Canarias (Maul, 1990), hasta Sudáfrica (Heemstra, 1986). En el Indo-Pacífico, se encuentra desde el
este de África, incluyendo Saya de Malha Bank (Fricke, 1999) hasta Japón, Hawai, Australia y Nueva Zelanda (Paulin et al., 1989). En Chile, si bien su distribución no está del todo definida, se ha reportado en
áreas próximas al archipiélago de Juan Fernández
(33º37’S-78º50’W) y en las islas Desventuradas
(26º20’S-80º07’W), mientras que en la costa continental se ha registrado en forma incidental frente a Caldera (27º03’S), Coquimbo (29º58’S) y Valparaíso
(33º30’S) (Lillo et al., 1999). Esta especie también ha
sido registrada en la región sur-austral de Chile, hasta
aproximadamente los 48ºS (Inada et al., 1986).
La pesquería chilena de alfonsino se desarrolla en
la cima de los montes pertenecientes al cordón submarino de Juan Fernández. Sus inicios datan de 1998, año
en que se desembarcaron 144 ton. De acuerdo a lo
indicado por Zuleta et al. (2008), las actividades extractivas asociadas a B. splendens entre 1998 y 2000,
corresponden a lances de pesca que se realizaban en
viajes cuyo objetivo era la captura de orange roughy
(Hoplostethus atlanticus) y sólo a partir del 2001 se
cambia el régimen operacional y se originan viajes
con intencionalidad de pesca dirigida al alfonsino. Por
su parte, el nivel de desembarque registrado en el
2000 (4.300 ton) evidencia que las actividades de
pesca se intensifican sobre B. splendens a partir de ese
año. Estos dos factores permiten suponer que el inicio
propiamente tal de la pesquería se efectuó entre los
años 2000 y 2001, con cifras ascendentes en los desembarque, los que continuaron hasta el 2003 (9.141
ton). En los años siguientes, los desembarques se redujeron, estabilizándose alrededor de 3.000 ton año-1
producto del establecimiento de cuotas globales de
captura.
El acelerado crecimiento de la pesquería de alfonsino durante ese período no fue acompañado en forma
paralela por un incremento en la investigación de este
recurso. Los estudios disponibles de la etapa temprana
se refieren sólo a estudios sobre el crecimiento realizados por Gili et al. (2002) y los correspondientes a
evaluaciones de biomasa a partir de cruceros de prospección, cuya finalidad también era determinar la
biomasa de orange roughy; no obstante, estos sólo se
realizan a partir del 2005.
Independiente de lo anterior, y por iniciativa de la
industria, la Escuela de Ciencias del Mar de la Pontificia Universidad Católica de Valparaíso, realizó actividades de monitoreo de faenas extractivas de alfonsino
durante el período 2001-2003. Considerando la escasa
disponibilidad de antecedentes que se tiene de la pesquería en sus primeros años de desarrollo, el presente
estudio tiene como objetivo caracterizar esa etapa de
la pesquería, tanto en términos operacionales como
biológicos, particularmente con el fin de determinar
las composiciones de tallas y tamaños medios de los
ejemplares capturados y determinar la talla de primera
madurez sexual del alfonsino.
Esta investigación se sustenta en el análisis de la información proveniente del monitoreo de faenas de
pesca comercial de alfonsino (Beryx splendens) en el
cordón submarino de Juan Fernández, realizado entre
octubre de 2001 y mayo de 2003. Las actividades de
pesca fueron ejecutadas con el PAM Boston Blenheim
mediante red de arrastre de cuatro paneles, modelo
Casanova, con tamaño de malla en el copo de 130
mm.
Se registró la información de la posición (latitud y
longitud) y duración (h) del lance, la profundidad
media de operación de la red (m) y captura total (kg)
de la especie objetivo y de la fauna acompañante
relevante. Una vez virado el arte y desplegada la
captura sobre cubierta y mientras la tripulación
encajonaba la especie objetivo, se separó en forma
aleatoria un número variable de ejemplares para el
muestreo biológico. El número de individuos
examinados dependió de la disponibilidad de tiempo
entre lances. A los ejemplares se les determinó el
sexo; mediante un ictiómetro (±1 cm) se midió la
longitud de horquilla (LH) y se determinó el grado de
madurez de sus gónadas, utilizando la escala
macroscópica propuesta por Lehodey et al. (1997).
Con la información obtenida se analizaron los registros de manera espacial (por zona de pesca) y temporalmente (mes/año). El área de operación se dividió
en tres zonas, que corresponden a los lugares donde se
concentra la especie objetivo: al este y al sur de la isla
Robinson Crusoe (montes JF1a y JF1b, respectivamente) y al este de estas últimas a aproximadamente
50 mn (monte JF2) (Fig. 1). En cada caso, se determinó la captura promedio por lance y el rendimiento
465
Pesca de Beryx splendens en montañas submarinas de Juan Fernández, Chile
79°00'W
78°40'
78°00'
78°20'
77°40'
Océano Pacífico
33°30'S
500
1000
400
1200
I. Robinsón Crusoe
1600
JF2
JF1a
300
300
33°40'
1800
275
300
250
100
200
200
JF1b
400
500
600
300
2200
800
500
800
800
1000
1000
Figura 1. Área de estudio y principales lugares de pesca de Beryx splendens, en el cordón submarino de Juan Fernández
(isóbatas en metros).
Figure 1. Study area and main fishing sites for Beryx splendens in the Juan Fernández seamount chain (isobaths in meters).
promedio en términos de kilos por hora de arrastre (kg
h.a.-1). Además, se georreferenciaron los lances de
pesca y las capturas, para lo cual se empleó el programa Surfer (Versión 8).
A partir de la información proveniente del muestreo de las capturas, se confeccionaron las respectivas
distribuciones de frecuencias de tallas, separadamente,
por sexo, mes y zona de pesca. Luego se determinó los
principales estadígrafos de la longitud de horquilla
(LH) de los ejemplares muestreados (media aritmética
y desviación estándar). En forma paralela, se determinó la proporción sexual global y a la talla, mientras
que los registros de madurez gonadal fueron agrupados por mes y zona de pesca. Además, se realizó la
determinación de la talla de primera madurez
(TMS50%) en machos y hembras, considerando que los
ejemplares con sus gónadas en estado de madurez ≥ 4,
se encontraban en proceso de maduración o ya maduros.
El modelo generalizado para la determinación de la
proporción de ejemplares maduros a la talla P(l) corresponde a:
P(l) = [ 1 + exp (α − β l)] −1
cuyos parámetros α y β fueron estimados mediante
Máxima Verosimilitud considerando que la variable
responde a una distribución binomial, donde el negativo de la función de log verosimilitud (Roa et al.,
1999) corresponde a la función:
l=
∑[ h ln (P(l) + (n − h ) ln (1 − P(l)]
l
l
l
l
quedando la talla al P% de madurez sexual expresada
por:
lp% =
1 ⎡1 ⎤ α
ln
−1 −
α ⎢⎣ P ⎥⎦ β
cuyo intervalo de confianza al 100(1-α)% es estimado
como:
IC = lp% + g (P) ± z a / 2
v(l p % )
donde
⎛ P ⎞
g( P) = ln ⎜
⎟
⎝1− P ⎠
y
v (lp% ) = v (α) + 2lp% cov (α, β) + l2p% v (β) .
en la cual zα / 2 es un cuantil de la distribución normal
estándar y cov(α, β) la covarianza entre los parámetros
tomada del inverso de la matriz hessiana. La talla de
primera madurez sexual (TMS50%) fue determinada
como la longitud en que el 50% de los ejemplares
estaban maduros. El modelo fue programado y resuelto en lenguaje Matlab.
RESULTADOS
El monitoreo de las operaciones de pesca se realizó
durante cinco etapas correspondientes a los periodos
en que se efectuaron las operaciones extractivas de
Beryx splendens: octubre y diciembre de 2001, marzo
y mayo 2002, y marzo 2003. En total, se efectuaron
187 lances, de los cuales 121 fueron exitosos en que se
466
sólo se registró mayor actividad de pesca en el 2002.
(Fig. 4). Al sur de la isla Robinson Crusoe (monte
JF1b), se registraron operaciones de pesca durante
todos los meses analizados y se obtuvo mayor rendimiento promedio, con valores de 5,4 ton lance-1 y 11,8
ton h.a.-1 (Tabla 4).
En las operaciones de pesca analizadas se muestrearon 14.773 ejemplares, de los cuales 6.064 fueron
machos y 8.709 hembras (Tabla 5). Se observó mayor
predominio de las hembras que representaron el 59%
de las capturas y la proporción sexual estructurada a la
talla mostró un predominio de machos a tallas inferiores a 24 cm LH (Fig. 5).
registraron 525,1 ton de alfonsino, que constituyó el
99,2% de la captura total (Tabla 1).
Dada la configuración de los fondos donde se concentra el alfonsino, los lances de pesca fueron de corta
duración, con un promedio de 0,8 h (Tabla 2). No
obstante, se observó un amplio rango de variación en
la extensión de los mismos, con la moda en el rango
0,26-0,50 h (Fig. 2). La profundidad media de pesca
fue 469,7 m y no se evidenciaron diferencias importantes entre zonas (Tabla 3), realizándose más del 70%
de los lances entre 451 y 500 m (Fig. 3).
Las faenas de pesca se efectuaron preferentemente
en las cercanías de la isla Robinson Crusoe, ejecutándose 84 lances en los montes JF1a, 70 en JF1b y 33 en
JF2, de los cuales el 60,7%, 72,8% y 57,6% registraron captura de alfonsino, respectivamente. Las actividades de pesca presentaron variación espacial entre
años. Durante el año 2001, los lances se efectuaron
principalmente en las cercanías de la isla Robinson
Crusoe y de manera más intensiva en el sector del
monte JF1a, situación que se reitera durante las opera
ciones efectuadas en marzo de 2003. En el monte JF2
El tamaño medio de los ejemplares fluctuó entre
34,6 y 36,8 cm LH en machos y entre 36,2 y 38,4 cm
LH en hembras, evidenciando el mayor tamaño de los
machos. En términos globales, los ejemplares provenientes de la zona JF1a registraron tallas levemente
superiores a los capturados en las otras dos zonas, con
promedios de 37,4 cm en JF1a y 36,1 y 36,2 cm en los
montes JF1b y JF2, respectivamente (Tabla 5).
Tabla 1. Número de lances, captura de alfonsino y captura total, por zona (monte submarino) y período de pesca.
Table 1. Number of hauls, alfonsino catches, and total catches per zone (seamount) and fishing period.
Mes
Zona de pesca
(monte)
Octubre 2001
JF 1a
JF 1b
JF2
Total
Diciembre
2001
Total
JF 1a
JF 1b
Marzo 2002
JF 1b
JF2
Total
Mayo 2002
JF 1b
JF2
Total
Marzo 2003
JF 1a
JF 1b
JF2
Total
Total zona
(monte)
Total general
JF 1a
JF 1b
JF2
N° de lances
Captura (ton)
Con captura
Sin captura
Total
Total
Alfonsino
21
4
2
27
17
15
32
17
4
21
14
12
26
13
1
1
15
51
51
19
121
7
8
5
20
9
2
11
6
4
10
2
4
6
17
1
1
19
33
19
14
66
28
12
7
47
26
17
43
23
8
31
16
16
32
30
2
2
34
84
70
33
187
98,4
24,7
2,0
125,1
61,0
54,7
115,6
114,2
3,4
117,6
81,0
41,2
122,2
47,0
1,3
0,3
48,5
206,3
275,8
46,9
529,1
97,6
24,7
2,0
124,4
60,4
54,2
114,7
112,7
3,2
115,9
81,0
41,2
122,2
46,5
1,2
0,3
48,0
204,6
273,8
46,7
525,1
467
Tabla 2. Media, varianza y desviación estándar en la duración de los lances (h).
Table 2. Average, variance, and standard deviation for the duration of the haul (h).
Período
Marzo
2002
Mayo
2002
0,2-3,3
0,1-1,0
0,2-1,6
0,2-2,9
0,2-3,3
0,1-1,6
0,2-2,9
0,2-3,0
0,2-1,7
0,2-3,0
1,4
0,5
0,5
1,0
Mínimo y
máximo (h)
Diciembre
2001
JF1a
JF1b
JF2
Area total
Media (h)
Octubre
2001
JF1a
JF1b
JF2
Area total
Desviación
estándar (h)
Zona de pesca
(monte submarino)
JF1a
JF1b
JF2
Area total
1,4
0,5
1,0
1,0
0,2
0,5
0,9
0,3
0,9
1,0
Marzo
2003
Total
período
0,1-1,6
0,1-1,6
0,1-3,3
0,2-3,0
0,1-1,7
0,1-1,7
0,5
0,5
1,0
0,8
0,6
0,9
0,3
0,3
0,8
0,8
0,4
0,8
0,8
0,7
0,8
0,7
0,7
0,7
madurez gonadal. Destacó la presencia de ejemplares
en post-desove (estado 7), registrada en los montes
JF1a y JF1b en diciembre 2001 y en JF2 en febrero
2002. En los muestreos realizados en otros meses
predominaron preferentemente los estados 2, 3 y 4
(Fig. 8).
El ajuste de los datos por Máxima Verosimilitud
correspondiente a los ejemplares maduros vs la talla
entregó los siguientes resultados en la matriz varianzacovarianza y los parámetros estimados fueron los siguientes:
Matriz varianza-covarianza
Figura 2. Distribución de frecuencias de la duración en
los lances de pesca.
Figure 2. Frequencies distribution of the duration of the
fishing hauls.
Machos
0,4123
0,0003
0,0117
v(α)
v(β)
cov(α,β)
Hembras
0,1472
0,0001
0,0041
Parámetros estimados
Las distribuciones de frecuencias de tallas en ambos sexos y por zona de pesca presentaron generalmente una unimodal (Figs. 6 y 7), con una moda principal entre 36 y 38 cm LH en machos, y entre 38 y 40
cm LH en hembras. No obstante, se encontró mayor
amplitud de tallas en marzo de 2002, cuando se registraron ejemplares de menor tamaño, generando un
segundo grupo modal alrededor de los 23 cm LH y
que básicamente corresponde a ejemplares provenientes del monte submarino JF1b (Fig. 6).
Según la época en que fueron capturados los ejemplares examinados presentaron distintos grados de
α
β
TMS50%
v(TMS50%)
Límite inferior TMS50%
Límite superior TMS50%
Machos
Hembras
19,158
0,559
34,25
1,56
31,87
36,63
11,039
0,331
33,34
0,53
31,95
34,73
La proporción de individuos en estado de madurez
≥ 4, indicó que los machos alcanzaron la primera madurez (TMS50%) a una talla superior que las hembras.
468
Tabla 3. Media, varianza y desviación estándar de la profundidad media de los lances de pesca.
Table 3. Average, variance, and standard deviation for the average depth of the fishing hauls.
Diciembre
2001
Marzo
2002
Mayo
2002
Mínimo y
máximo
(m)
Zona de pesca
(monte submarino)
JF1a
JF1b
JF2
Area total
441-508
365-540
463-495
440-485
441-508
365-540
440-485
420-520
430-528
420-528
JF1a
JF1b
JF2
Area total
JF1a
JF1b
JF2
468,6
474,3
472,9
465,2
Desviación
estándar
(m)
Octubre
2001
Media (m)
Período
Area total
468,6
17,8
474,0
34,3
9,5
17,8
29,9
N = 121
% de lances
80
60
40
20
0
351-400
401-450
451-500
501-550
551-600
Rango de profundidad (m)
Figura 3. Distribución batimétrica (m) de los arrastres de
pesca de alfonsino.
Figure 3. Bathymetric distribution (m) of trawls for
alfonsino.
En efecto, los machos la alcanzaron a los 34,2 cm
LH y las hembras a los 33,3 cm LH (Fig. 9), no existiendo diferencias significativas en la talla de madurez
entre ambos sexos.
DISCUSIÓN
La historia de esta pesquería, muestra un rápido desarrollo en un lapso reducido. Esto adquiere especial
connotación si se considera que Beryx splendens es
una especie de crecimiento lento asociada a ecosiste-
465,2
11,8
11,8
Marzo
2003
400-545
400-545
Total período
365-540
420-520
400-545
365-545
467,0
481,5
469,3
469,7
469,7
24,5
43,4
50,7
471,3
467,2
472,2
469,7
26,7
18,1
48,3
27,5
50,7
28,1
mas de aguas profundas y que tasas de explotación
altas podrían ocasionar daños importantes a la población y dificultar su recuperación, elementos que pondrían en riesgo la sustentabilidad de esta pesquería.
Como es frecuente en este campo, el grado de conocimiento del recurso tiene un marcado rezago respecto de la actividad extractiva. Así por lo general, la
recopilación sistemática de información comienza
cuando ya las faenas se han consolidado y difícilmente
se dispone de datos que permitan caracterizar el stock
de alfonsino en la etapa de desarrollo inicial de la
pesquería, por lo que difícilmente se puede visualizar
sus cambios antes variaciones tan importantes de explotación como las registradas en los años 2002 y
2003. En este sentido, la información analizada en esta
investigación tiene justamente esa relevancia por
cuanto los datos provienen de la etapa inicial de su
desarrollo y eventualmente, puede constituir un punto
de referencia hacia el futuro.
Una de las particularidades de esta pesquería radica
en la maniobra de arrastre, la que requiere gran habilidad de capitanes y tripulaciones experimentadas. Debido a que la operación se tiene que realizar con precisión y velocidad para interceptar la concentración de
peces en fondos de configuración irregular. De acuerdo a los resultados obtenidos, los lances exitosos por
lo general no superaron los 20 min de duración, tiempo que puede ser inferior, si se considera que los registros de bitácora usualmente toman en cuenta tiempos
469
79°00'W
78°40'
2001
Octubre
Diciembre
78°00'
78°20'
77°40'
Océano Pacífico
33°30'S
500
1000
400
1200
I. Robinsón Crusoe
1600
1800
300
300
33°40'
275
300
250
100
200
200
400
500
600
300
2200
800
500
800
800
1000
1000
79°00'W
78°40'
2002
Marzo
Mayo
33°30'S
78°00'
78°20'
77°40'
Océano Pacífico
500
1000
400
1200
I. Robinsón Crusoe
1600
1800
300
300
33°40'
275
300
250
100
200
200
400
500
600
300
2200
800
500
800
800
1000
1000
79°00'W
78°40'
2003
Octubre
78°00'
78°20'
77°40'
Océano Pacífico
33°30'S
500
1000
400
1200
I. Robinsón Crusoe
1600
1800
33°40'
300
300
275
300
250
100
200
200
400
500
600
300
2200
500
800
800
800
1000
1000
Figura 4. Distribución de lances de pesca de alfonsino por período y zona de pesca (isóbatas en metros).
Figure 4. Distribution of hauls for alfonsino by period and fishing zone (isobaths in meters).
470
Tabla 4. Número de lances con captura y rendimiento promedio de alfonsino por zona y período de pesca.
Table 4. Number of hauls with catches and average alfonsino yields per zone and fishing period.
Zona de pesca (monte submarino)
JF1a
Período de pesca
N° lances con
captura
JF1b
Rendimiento
ton
h.a.-1
9,4
N° lances
con captura
Area total
JF2
Rendimiento
4
ton
lance-1
6,2
ton
h.a.-1
19,0
N° lances
con captura
Rendimiento
ton
ton
lance-1 h.a-1
1,0
1,8
N° lances
con captura
Rendimiento
27
ton
lance-1
4,6
ton
h.a.-1
10,3
Octubre 2001
21
ton
lance-1
4,7
Diciembre 2001
17
3,6
6,3
15
3,6
13,3
-
-
-
32
3,6
6,6
Marzo 2002
-
-
-
17
6,6
7,5
4
0,8
2,5
21
5,5
6,5
Mayo 2002
-
-
-
14
5,5
13,8
12
3,4
6,7
26
4,7
10,5
Marzo 2003
13
3,6
8,8
1
1,2
7,4
1
0,3
3,4
15
3,2
8,3
Total
51
4,0
8,2
51
5,4
11,8
19
2,5
5,1
121
4,3
9,2
2
471
Tabla 5. Número de ejemplares muestreados (N), valor promedio y desviación estándar de la longitud horquilla en alfonsino.
Table 5. Number of specimens sampled (N), average value, and standard deviation of the fork length in alfonsino.
Zona de pesca (monte submarino)
Area total
N
Machos
1.799
JF1a
Media
(cm)
Desviación
estándar
(cm)
35,7
3,6
JF1b
Media
(cm)
Desviación
estándar
(cm)
1.353
36,1
3,6
N
N
329
JF2
Media
(cm)
Desviación
estándar
(cm)
35,1
3,0
N
117
Media
(cm)
Desviación
estándar
(cm)
33,2
4,2
Hembras
3.106
37,6
4,3
2.372
38,2
4,1
526
36,3
3,5
208
34,0
5,6
Total
4.905
36,9
4,2
3.725
37,4
4,1
855
35,8
3,4
325
33,7
5,2
996
35,5
2,7
375
35,9
3,1
621
35,2
2,5
Machos
Hembras
1.330
37,2
3,3
618
38,1
3,6
712
36,4
2,9
Total
2.326
36,4
3,2
993
37,3
3,6
1.333
35,8
2,8
Machos
1.272
34,6
5,1
Hembras
1.738
36,2
5,2
Total
3.010
35,5
5,2
Machos
1.460
36,5
2,9
Hembras
1.772
37,5
3,4
Total
3.232
37,0
3,2
537
36,8
3,4
Machos
Hembras
Sin captura
Sin captura
468
36,6
3,5
Sin captura
1.121
34,3
5,2
151
36,7
2,8
1.512
35,9
5,3
226
37,8
3,6
2.633
35,2
5,3
377
37,4
3,3
830
37,0
2,8
630
35,7
2,9
1.042
38,0
3,3
730
36,8
3,5
1.872
37,6
3,1
1.360
36,3
3,3
39
37,0
3,2
30
39,5
2,1
763
38,4
3,8
680
38,4
3,9
60
38,0
2,9
23
40,7
2,7
Total
1.300
37,8
3,8
1.148
37,7
3,8
99
37,6
3,1
53
40,0
2,5
Machos
6.064
35,7
3,8
2.196
36,2
3,5
2.940
35,4
4,0
928
35,7
3,3
Hembras
8.709
37,3
4,2
3.670
38,2
4,0
3.852
36,7
4,3
1.187
36,6
4,2
Total
14.773
36,6
4,1
5.866
37,4
4,0
6.792
36,1
4,2
2.115
36,2
3,8
472
100
% de machos
80
60
40
20
0
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
Longitud horquilla (cm)
Figura 5. Proporción sexual estructurada a la talla (porcentaje de machos) en alfonsino.
Figure 5. Size-structured sexual proportion (percentage
of males) in alfonsino.
no necesariamente involucrados en la ejecución efectiva del lance. De acuerdo a antecedentes disponibles
sobre la pesquería de alfonsino que en Nueva Zelanda,
los lances no exceden 10 min de duración, lo que es
atribuible a la configuración del fondo y también a la
necesidad de no acumular demasiada pesca en el copo,
a fin de asegurar la buena calidad de los ejemplares
capturados.
En términos operacionales, los resultados obtenidos indican que en los inicios de la pesquería las operaciones de pesca se desarrollaron en tres zonas de
pesca cercanas a la isla Robinson Crusoe, las cuales,
de acuerdo a los resultados obtenidos en estudios recientes (Niklitschek et al., 2007a, 2007b, Roa et al.,
2008, Zuleta et al., 2008) se han mantenido hasta la
actualidad, aunque durante los últimos años se han
incorporado nuevas elevaciones submarinas, pero
igualmente pertenecientes al cordón de Juan Fernández. Independiente, las zonas más intensamente explotadas corresponden a los montes JF1, y principalmente
el monte JF1b.
Los rendimientos estimados presentaron tendencia
fluctuante entre temporadas con un promedio global
de 4,3 ton lance-1 y 9,2 ton h.a.-1. Cabe destacar que
durante el último período monitoreado se obtuvo un
promedio inferior al registrado a inicios de la temporada, lo que posiblemente es consecuencia del mayor
grado de explotación del alfonsino. De acuerdo a la
estimación de rendimientos realizados por Young et
al., 2008 (en Zuleta et al., 2008), la tendencia ha sido
variable aunque acentuándose un patrón descendente
en los últimos años, con valores en 2006 de 2,5 ton
lance-1 y 5,7 ton h.a.-1, lo que muestra un mayor grado
de explotación de alfonsino.
La captura de alfonsino en estos montes submarinos revelan una menor presencia de machos, lo cual
coincide con lo señalado por Niklitschek et al. (2007a)
en el alfonsino capturado en 2006 y lo indicado por
Roa et al. (2008) para el período 2004-2007 en esta
misma área. Esto difiere de la relación 1:1 entre los
sexos señalada por Lehodey et al. (1997) para Nueva
Caledonia. De igual manera los resultados obtenidos
en el presente estudio muestran la dominancia de las
hembras a tallas superiores, lo que se puede atribuir a
la mayor tasa de crecimiento de este sexo (Massey &
Horn, 1990; Lehodey & Grandperrin, 1996; Gili et al.,
2002) y/o a que los machos experimentarían una mayor mortalidad.
El tamaño medio de los ejemplares capturados en
las diferentes épocas fluctuó entre 34,6 y 36,8 cm LH
en machos y entre 36,2 y 38,4 cm LH en hembras. Al
contrastar estos valores con los indicados en 2005,
2006 y 2007 (Niklitschek et al., 2007a, 2007b; Roa et
al., 2008), se observó una disminución en la talla media de los ejemplares.
De acuerdo a la literatura disponible, el alfonsino
capturado en aguas de jurisdicción nacional presenta
una talla media mayor a la reportada en otras áreas
marinas. Por ejemplo, en la pesquería desarrollada en
Nueva Zelanda, los ejemplares registran tallas entre 20
y 30 cm LH, con dos modas claramente identificadas
(20-22 y 24-25 cm) (Langley & Walker, 2002). Así
también, en general, las capturas provenientes de faenas de arrastre vulneran ejemplares con tallas menores
a las obtenidas con espineles (Seki & Tagami, 1986).
No obstante, es probable que esto se deba a la estratificación de tallas en términos de profundidad; pues
Lehodey et al. (1994), señalan un significativo aumento del tamaño de los ejemplares a medida que aumenta
la profundidad.
En la distribución de frecuencia de talla correspondiente al monte JF1b, se detectaron dos grupos modales relevantes (Fig. 6), lo cual coincide con lo reportado por otros autores (Lehodey et al., 1997; Langley &
Walker, 2002). No obstante, no existe una clara explicación de este efecto, aunque se podría atribuir a movimientos migracionales u otros procesos de la dinámica del stock asociados al reclutamiento, reproducción o crecimiento, entre otros.
Además, los resultados obtenidos permiten determinar el período en que se reproduce el alfonsino en el
cordón submarino Juan Fernández, así como la talla en
que maduran ambos sexos. De acuerdo a los datos
reunidos, entre octubre 2001 y mayo 2002, se observaron ejemplares en diferentes estados de madurez en
los meses y en zonas analizadas (Fig. 8). Sin embargo,
en los registros realizados en marzo y mayo, se observó la mayor proporción de estadios de madurez avanzada y la presencia de ejemplares desovados, lo que
MACHOS
N = 1.799
HEMBRAS
18
16
14
12
10
8
6
4
2
0
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
N = 1.272
N = 1.460
18
16
14
12
10
8
6
4
2
0
18
16
14
12
10
8
6
4
2
0
N = 1.772
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
N = 763
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Longitud horquilla (LH) cm
Figura 6. Distribución de frecuencias de tallas en alfonsino, por sexo y temporada de pesca.
Figure 6. Size frequencies distributions in alfonsino by sex and fishing season.
N = 3.010
N = 3.232
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
N = 1.300
Marzo 2003
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
Mayo 2002
N = 537
N = 1.738
N = 2.326
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
18
16
14
12
10
8
6
4
2
0
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
N = 1.330
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Marzo 2002
Frecuencia relativa (%)
N = 996
N = 4.905
Diciembre 2001
18
16
14
12
10
8
6
4
2
0
N = 3.106
TOTAL
18
16
14
12
10
8
6
4
2
0
Ooctubre 2001
18
16
14
12
10
8
6
4
2
0
473
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
474
MACHOS
N = 2.196
18
16
14
12
10
8
6
4
2
0
18
16
14
12
10
8
6
4
2
0
N = 2.940
18
16
14
12
10
8
6
4
2
0
N = 928
18
16
14
12
10
8
6
4
2
0
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
N = 8.709
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Longitud horquilla (LH) cm
Figura 7. Distribución de frecuencias de tallas en alfonsino, por sexo y zona de pesca.
Figure 7. Size frequencies distributions in alfonsino by sex and fishing zone.
N = 2.115
18
16
14
12
10
8
6
4
2
0
N = 14.773
TOTAL
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
N = 1.187
N = 6.792
Monte JF2
N = 6.064
18
16
14
12
10
8
6
4
2
0
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
N = 3.852
N = 5.866
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
18
16
14
12
10
8
6
4
2
0
18
16
14
12
10
8
6
4
2
0
Monte JF1b
Frecuencia relativa (%)
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
N = 3.670
TOTAL
Monte JF1a
18
16
14
12
10
8
6
4
2
0
HEMBRAS
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
475
MONTE JF1a
2
3
4
5
6
3
4
5
6
3
4
5
6
7
7
1
2
3
4
5
6
7
MACHOS
3
4
5
6
7
N = 226
1
2
3
4
1
1
2
3
4
5
6
5
N = 30
1
2
3
4
5
6
70
60
50
40
30
20
10
0
7
7
7
3
4
5
6
6
7
N = 826
1
2
3
4
5
6
70
60
50
40
30
20
10
0
2
3
4
5
6
4
5
60
40
20
20
6
7
2
3
4
5
6
7
N = 1.044
0
2
3
4
5
6
7
N = 39
1
2
3
4
5
80
60
60
40
40
20
20
6
7
N = 60
0
2
3
4
5
6
7
1
ESTADO DE MADUREZ
7
N = 23
1
3
N = 1.516
1
40
0
N = 731
2
80
60
80
7
1
70
60
50
40
30
20
10
0
MARZO 2003
70
60
50
40
30
20
10
0
6
MAYO 2002
FRECUENCIA RELATIVA (%)
N = 620
2
80
1
70
60
50
40
30
20
10
0
5
N = 709
MARZO 2003
2
4
N = 1.117
1
70
60
50
40
30
20
10
0
FEBRERO 2002
1
3
0
HEMBRAS
N = 152
2
70
60
50
40
30
20
10
0
70
60
50
40
30
20
10
0
MAYO 2002
MONTE JF2
70
60
50
40
30
20
10
0
N = 622
1
N = 676
ESTADO DE MADUREZ
HEMBRAS
70
60
50
40
30
20
10
0
FEBRERO 2002
2
2
70
60
50
40
30
20
10
0
N = 459
1
1
7
MACHOS
N = 615
MARZO 2003
70
60
50
40
30
20
10
0
70
60
50
40
30
20
10
0
N = 372
DICIEMBRE 2001
70
60
50
40
30
20
10
0
1
MONTE JF1b
HEMBRAS
DICIEMBRE 2001
MACHOS
7
ESTADO DE MADUREZ
Figura 8. Estados de madurez de alfonsino capturado en diferentes montes del cordón submarino de Juan Fernández.
Figure 8. Maturity states in alfonsino caught on different seamounts in the Juan Fernández chain.
2
3
4
5
6
7
476
sería indicativo que la reproducción de se realiza en el
período invernal.
La determinación de la época de reproducción en
esta región del Pacífico en invierno coincide con el
resultado obtenido en Nueva Zelanda, donde el máximo reproductivo ocurre en julio-agosto (Horn & Massey, 1989). Pese a ello, estudios realizados en otras
zonas del hemisferio austral sugieren algo diferente,
como por ejemplo que en el Atlántico sur-este esta
especie se reproduciría entre enero y marzo (Alekseev
et al., 1986), mientras que en aguas de Nueva Caledonia de noviembre a febrero (Lehodey & Grandperrin,
1996; Lehodey et al., 1997). Los resultados obtenidos
hasta ahora deben considerarse como preliminares y
deberán ser corroborados, al disponer de información
que abarque a lo menos un ciclo anual de muestreo.
La talla de primera madurez sexual (TMS50%) establecida a los 34,3 cm LH en machos y a los 33,3 cm
en hembras (Fig. 9) significa que los ejemplares alcanzarían esta talla en el rango de edad entre 5 y 6
años, de acuerdo a los parámetros de crecimiento estimados por Gili et al. (2002). De acuerdo a la longitud infinita determinada por estos últimos autores, la
TMS50% la alcanzarían los machos al 54% y las hembras al 57% de dicha longitud.
Hembras
1,2
1,0
0,8
0,6
Proporción de ejemplares maduros
0,4
0,2
TMS50% = 33,3 cm
0,0
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
Machos
1,2
1,0
0,8
0,6
0,4
0,2
Los valores determinados en esta investigación difieren con lo reportado por Roa et al. (2008) para alfonsinos capturados en estos mismos montes submarinos, donde determinaron una talla de primera madurez
en hembras de 40 cm LH, sobre la base de observaciones histológicas de las gónadas. Cabe destacar que
estos autores señalan que la escala macroscópica empleada ha sido mal aplicada, clasificando peces maduros como inmaduros lo que explicaría que se hayan
identificado tan pocos peces maduros en las zonas de
pesca a lo largo de la historia de esta pesquería.
Por otra parte, los resultados obtenidos son prácticamente similares a los encontrados por Lehodey et al.
(1997) en Nueva Caledonia, donde la TMS50% se
determinó a 34,5 cm LH en machos y en 33,2 cm LH
en hembras. Así también, Masuzawa et al. (1975)
encontraron que los alfonsinos que desovan en el sur
de Japón tienen tallas superiores a 34 cm LH.
De acuerdo a los resultados de este estudio y a la
luz de los resultados obtenidos por otros autores, queda en evidencia que el stock de alfonsino explotado en
Juan Fernández ha experimentado una evolución decreciente en indicadores claves como son los rendimientos de pesca y la estructura de tallas, especialmente la talla media, lo cual se debería a las altas tasas
de explotación que fueron aplicadas sobre un recurso
que puede ser clasificado como de productividad moderada (González et al., 2003). No obstante, aun quedan temas importantes que estudiar, especialmente los
relacionados con aspectos reproductivos, que a nivel
nacional han estado sujetos a permanente discusión.
Finalmente, se puede destacar que la pesquería del
alfonsino y del orange roughy (Hoplostethus atlanticus) realizada en este mismo cordón submarino, representan dos recursos de alto interés y valor comercial.
Por esta misma razón, así como por el hecho que estas
especies son de crecimiento lento, bajo potencial reproductivo y el hecho que se concentran en lugares tan
específicos como las cumbres de los montes submarinos y en periodos claramente definidos, requiere de
especial preocupación de parte de la comunidad científica y autoridades, con el fin de apoyar la investigación de estas especies para contribuir a su sustentabilidad.
TMS50% = 33,3 cm
AGRADECIMIENTOS
0,0
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
Longitud horquilla (cm)
Figura 9. Función de madurez estimada para alfonsino y talla de primera madurez (TMS50%).
Figure 9. Estimated maturity function for alfonsino
and size of first maturity (TMS50%)
Los autores agradecen la colaboración brindada por el
capitán y tripulantes del PAM Boston Blenheim, nave
en la cual se realizó el primer monitoreo de esta especie. Así también a los Sres Reinaldo Rehhof
(Q.E.P.D.) y Raúl Bustos, por las labores de recolección de la información en las nueve mareas efectuadas
con este fin. Así también, se agradece a los Sres. Enri-
que Gutiérrez F., Gerente de Operaciones y Francisco
González, Jefe de Flota, ambos de la empresa Pesca
Chile S.A., por su apoyo y facilidades para realizar
esta investigación. Igualmente se reconoce a los revisores anónimos sus comentarios y sugerencias al documento.
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Lat. Am. J. Aquat. Res., 37(3): 479-500, 2009
Montes submarinos de Nazca y Salas y Gómez
479
Review
Montes submarinos de Nazca y Salas y Gómez: una revisión para el manejo
y conservación
Mauricio Gálvez-Larach
Environment, Society and Design Division, Lincoln University, Lincoln 7647, Canterbury, New Zealand
Dirección actual: WWF-Chile, Carlos Anwandter 624, Casa 4. Valdivia, Chile
RESUMEN. Con motivo de la creciente preocupación internacional por el manejo y conservación de ecosistemas marinos vulnerables, entre los que se cuentan los montes submarinos y los corales de aguas frías de las
cordilleras de Nazca y Salas y Gómez, y en vista de la inminente creación de la Organización Regional de
Administración Pesquera del Pacifico Sur, se hace necesaria una revisión de los principales antecedentes científicos sobre estas cadenas montañosas como un insumo para la toma de decisiones. El presente documento
atiende dicha necesidad considerando los aspectos geológicos, oceanográficos, biológicos, ecológicos y pesqueros asociados a Nazca y, Salas y Gómez, junto con identificar las opciones de manejo. A pesar que los estudios en el área son escasos y fragmentados, se destaca su particularidad debido a los altos niveles de endemismo, alta diversidad de especies, alta concentración de montes submarinos, presencia de corales de aguas
frías, mayor nivel de productividad en relación a las aguas circundantes y su potencialidad para actividades de
océano-minería y pesca de fondo. Debido a la lejanía del área y los altos costos involucrados, una mayor cooperación internacional se requerirá para abordar futuros estudios, al tiempo que la creación de una red de Áreas Marinas Protegidas se identifica como la mejor opción para el manejo y conservación.
Palabras clave: montes submarinos, Nazca y Salas y Gómez, ecosistemas marinos vulnerables, manejo pesquero y conservación.
Seamounts of Nazca and Salas y Gómez: a review for management and
conservation purposes
ABSTRACT. Due to growing international awareness of the importance of the conservation and management
of vulnerable marine ecosystems – of which the seamounts and deep-sea corals of the Nazca and Salas y
Gómez submarine ridges are examples – and taking into account the imminent establishment of a South Pacific Regional Fisheries Management Organization, a scientific review of this seamount chain is needed to
provide input for decision-making processes. This paper provides such a review, considering geological,
oceanographic, biological, ecological, and fisheries issues associated with Nazca and Salas y Gómez, and also
identifies some management options. Notwithstanding the limited and fragmented studies available, this distinctive area has a high level of endemism, rich biodiversity, seamount density, deep-sea corals, relatively elevated primary productivity (considering the surrounding waters), and the potential for bottom fisheries and
ocean-mining activities. Because of the remoteness of the area and the high costs involved, strong international cooperation will be required to undertake future studies. A network of Marine Protected Areas is identified as the best management option for the area.
Keywords: seamounts, Nazca and Salas y Gómez, vulnerable marine ecosystem, conservation and fisheries
management.
________________________
Corresponding author: Mauricio Gálvez ([email protected])
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INTRODUCCIÓN
La protección de los ecosistemas marinos vulnerables
(EMV) ha estado en la discusión pesquera internacional en los últimos años (Gálvez, 2007), siendo los
montes submarinos (MS) y los corales de aguas frías
los ecosistemas que enfrentan las amenazas más inmediatas. Esta preocupación, junto con la reciente
iniciativa internacional para crear la Organización
Regional de Administración Pesquera del Pacífico Sur
(ORAP PS), ha puesto de manifiesto a dos importantes
cordilleras submarinas que se extienden tanto en aguas
de la alta mar como en aguas jurisdiccionales de Chile, a saber, las cordilleras de Nazca y Salas y Gómez
(Fig. 1). Las bases para cualquier acción de manejo en
ésta área deberán descansar, entre otros aspectos, sobre los mejores antecedentes científicos disponibles,
por lo que una revisión de tales antecedentes resulta
necesaria. Una revisión integral de la bibliografía
científica disponible, no sólo es útil para aspectos de
manejo, sino que además permite identificar los vacíos
existentes, el diseño de nuevas investigaciones y el
planteamiento de hipótesis científicas a explorar. En
atención a esto, la presente revisión tiene por objetivo
resumir la información disponible en relación a aspectos geológicos, oceanográficos, biológicos, ecológicos
y pesqueros de Nazca y Salas y Gómez, al tiempo que
proporciona una visión general de los impactos que se
podrían derivar de la pesca y de las amenazas que
enfrentan. Finalmente, se analiza el manejo actual del
área y se consideran opciones de política orientadas a
la conservación y estudio de los ecosistemas que sustentan estas importantes cordilleras submarinas.
ESTADO DEL CONOCIMIENTO DE LOS
MONTES SUBMARINOS
Mientras la existencia de MS ha sido conocida por
cientos de años, la biología de los mismos recibió
escasa atención o esfuerzos de investigación hasta
fines de 1950 (Hubbs, 1959). Incluso hoy, sólo una
pequeña proporción de las decenas de miles de MS
estimados han sido biológicamente muestreados
(Clark et al., 2004) (Fig. 1). En una revisión de la
biología de los MS, Wilson & Kaufmann (1987) reportaron que cerca de 96 MS habían sido biológicamente muestreados. Desde entonces el número se ha
incrementado a cerca de 300. Pero incluso estas bajas
cifras sobreestiman lo que es conocido acerca de la
ecología de los MS. Esto es por una razón muy simple, la mayoría de los MS han sido muestreados de
oportunidad – con pocas muestras biológicas tomadas
durante estudios geológicos o de columna de agua, por
ejemplo – o muestreados sólo para algunos tipos de
animales o plantas marinas. Es raro disponer de estudios ecológicos comprehensivos. Varios de estos
eventos de muestreo han sido reportados en la literatura sólo como resúmenes abreviados de datos, sin una
lista completa de las especies colectadas o información de abundancia. Adicionalmente, mucho del trabajo publicado es de difícil acceso y arduo de sistematizar en una base común, dado que ha sido publicado en
diferentes lenguajes, a menudo en literatura gris como
reportes de gobierno difíciles de ubicar y/o acceder.
Las áreas de MS con los muestreos biológicos más
comprehensivos y para las cuales los resultados están
publicados en literatura ampliamente disponible en
idioma inglés se muestran en la Figura 1. Adicionalmente, una gran cantidad de información soviética de
MS alrededor del mundo se ha puesto a disposición a
través de Internet por parte del Instituto de Oceanología P.P. Shirshov (SeamountOnline, 2007). La biología de los MS es actualmente un área activa de investigación científica, prueba de ello son el Global Census of Marine Life on Seamounts (CenSeam) al amparo del NIWA de Nueva Zelanda, las investigaciones
del CSIRO de Australia en MS y las patrocinadas por
Fisheries and Ocean de Canadá, el programa Ocean
Explorer de la NOAA de USA, el proyecto OASIS de
varias instituciones europeas de investigación, y las
diferentes bases de datos públicas que se han levantado en Internet.
El impacto de la pesca sobre MS ha estado también
en el centro de la discusión científica. A pesar de que
Stone et al. (2004) indican que no existen verdaderos
muestreos en MS antes y después de actividades de
pesca comerciales – particularmente de pescas de
arrastre –, y por lo tanto se desconoce el impacto de la
misma sobre estos ecosistemas, se ha documentado
que los corales de aguas frías tienen requerimientos de
hábitat muy específicos y que pueden ser sensibles a la
alteración del carácter del fondo marino por parte de
artes de pesca, o a la creciente sedimentación resultante del arrastre de fondo (Commonwealth of Australia,
2002; ICES, 2006). Tales eventos pueden inhibir permanentemente la recuperación de arrecifes de coral de
aguas frías o de jardines de octocoral (Rogers, 1999;
ICES, 2006). Por otro lado, Koslow et al. (2001) en un
estudio cercano a una comparación de un “antes y
después” demuestran claramente el efecto del arrastre
de fondo al constatar la gran disminución en la cobertura de formas de vida en el fondo marino, la reducción de la diversidad de especies, y la baja generalizada de abundancia en los MS de Nueva Caledonia que
fueron objetos de pesca. Se ha señalado que los efectos adversos sobre MS deben ser analizados caso a
caso; sin embargo, Morato et al. (2004, 2006) efectúan
481
Figura 1. Distribución de 14.300 MS estimados (puntos grises). Los cuadrados muestran los montes biológicamente
muestreados en forma extensiva, los círculos indican algún nivel de datos biológicos y los triángulos indican montes
muestreados biológicamente pero cuyos datos no están disponibles en SeamountOnline (Clark et al., 2004). A: Cadenas
Hawaianas y Emperador, B: Montes del Pacífico medio, C: Cordón de Norfolk, D: Cordón de Lord Howe, E: Cordón
Chatman, F: Cordón Tasmania, G: Cadenas de Nazca y Salas y Gómez, H: Monte Gran Meteoro.
Figure 1. Distribution of 14,300 estimated seamounts (gray points). Squares indicate seamounts with comprehensive
biological data, circles indicate seamounts with some level of biological data, and triangles indicate seamounts that have
been sampled biologically but for which data are not available in SeamountOnline (Clark et al., 2004). A: HawaiianEmperor seamount chain, B: Mid-Pacific rise, C: Norfolk Ridge, D: Lord Howe rise, E: Chatman rise, F: Tasman rise, G:
Nazca and Salas y Gómez rises, H: Great Meteor seamount.
un análisis general y demuestran la alta vulnerabilidad
de las poblaciones de peces que habitan los MS.
Salvo el proyecto de investigación INSPIRE centrado en los hidratos de gas submarino, en que participan científicos nacionales, Chile ha estado ajeno a las
costosas investigaciones multidisciplinarias que implica el estudio de ambientes marinos de aguas profundas. No obstante, sobre aquellos montes que conforman las cordilleras de Nazca y Salas y Gómez se han
realizado algunas investigaciones extranjeras de gran
nivel, cuyos resultados aportan una comprensión suficiente de su riqueza y rareza biológica, y un entendimiento de la formación geomorfológica del área. Con
todo, los datos e información disponibles para esta
distintiva área marina son fragmentados, mucha información está dispersa en reportes de uso privado y
hasta la fecha no ha sido sintetizada con una visión
integradora.
Las investigaciones científicas de expediciones rusas y soviéticas entre 1973 y 1987 en Nazca y Salas y
Gómez, permitieron disponer de antecedentes inéditos
y comprehensivos respecto de la fauna asociada a
estos cordones montañosos, apreciándose sus caracte-
rísticas únicas, tanto por la diversidad de especies
como por el sorprendente grado de endemismo (Parin
et al., 1997; Mironov et al., 2006). En otro campo,
algunos estudios geológicos se han efectuado en el
área, principalmente por parte de expediciones europeas y de USA, lo que ha permitido una mejor comprensión de la formación de dichas cadenas de montes,
se ha precisado con alta resolución la batimetría de
gran parte del área, al tiempo que se han determinado
zonas ricas en minerales. Sin embargo, tanto los estudios biológicos como geológicos no han abarcado
todos los principales MS de estos cordones, quedando
con información parcial algunos montes de la parte
central de la cordillera de Salas y Gómez, y particularmente con un escaso nivel de información biológica
las áreas bajo jurisdicción chilena. Algunas expediciones oceanográficas realizadas por Chile se han efectuado en el área en el marco del programa CIMAR
Islas Oceánicas (Fig. 2), aunque éstas no han sido
orientadas específicamente a estudiar la dinámica
oceánica asociada a los MS. La información biológica
obtenida en el área, por los programas de observadores
a bordo de la flota comercial chilena de alta mar, está
fundamentalmente centrada en especies objetivo y el
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Figura 2. Localización de los cordones de MS de Salas y Gómez y Nazca. Rectángulos blancos indican montes con información geológica (Seamount Biogeosciences Network), números indican montes con información biológica (SeamountOnline), recta con puntos indican las estaciones oceanográficas del Crucero Cimar 5 Islas Oceánicas (Centro Nacional de Datos Oceanográficos de Chile), triángulos azules y rojos indican muestras de nódulos de manganeso y de corteza de cobalto-ferromanganeso (International Seabed Authority). En rojo se muestran las ZEEs insulares de Chile. Nombres asignados por expediciones rusas: 1 Needle, 2 Rock, 3 Ichthyologists, 4 Pillar, 5 Cupole, 6 Mayday, 7 Pearl, 8 Amber, 9 Western, 10 Baral, 11 Long, 12 Bolshaya, 13 Communard (Nasca 5), 14 New, 15 Dorofeev, 16 Albert, 17 Ikhtiandr, 18 Ecliptic, 19 Professor Mesyatzev, 20 Star, 21 Initial, 22 Soldatov, 23 Nasca 7, Nombres asignados por expediciones Chilenas: 24 Nazca #3, 25 Nazca #5, 26 Nazca #7, 27 Nazca #6, 28 Nazca #8.
Figure 2. Location of Salas y Gómez and Nazca seamount chain. White rectangles indicate seamounts with geological
data (Seamount Biogeosciences Network), numbers indicate seamounts with biological data (SeamountOnline), black
lines with dots indicate oceanographic sampling points from Cimar 5 Islas Oceánicas research cruise (Centro Nacional de
Datos Oceanográficos de Chile), and blue and red triangles indicate manganese nodules and cobalt-enriched ferromanganese crust samples (International Seabed Authority). The Chilean EEZs are circled in red. Seamount names given by
Russian expeditions are: 1 Needle, 2 Rock, 3 Ichthyologists, 4 Pillar, 5 Cupole, 6 Mayday, 7 Pearl, 8 Amber, 9 Western,
10 Baral, 11 Long, 12 Bolshaya, 13 Communard (Nasca 5), 14 New, 15 Dorofeev, 16 Albert, 17 Ikhtiandr, 18 Ecliptic, 19
Professor Mesyatzev, 20 Star, 21 Initial, 22 Soldatov, 23 Nasca 7. Seamount names given by Chilean expeditions are: 24
Nazca #3, 25 Nazca #5, 26 Nazca #7, 27 Nazca #6, 28 Nazca #8.
muestreo de la fauna acompañante no es total. Si bien
es cierto que el conocimiento global de los MS está
lejos de ser completo, para el caso de Nazca y Salas y
Gómez, se ha obtenido información suficiente que
debiera motivar el desarrollo de futuras investigaciones multidisciplinarias, a fin de disponer de un nivel
de comprensión que permita una adecuada administración del área. Los países costeros de la cuenca suroriental de océano Pacífico, y en particular Chile, debieran tener un rol preponderante en dichas investigaciones, no sólo por el avance que esto debe suponer
para sus científicos, sino que además por la responsabilidad que les cabe a estas naciones en la conservación de estas únicas cordilleras submarinas.
GEOCEANOFRAFÍA DEL AREA
Geomorfología y formación
Los MS de Nazca y Salas y Gómez en conjunto son
uno de los accidentes geográficos submarinos más
relevantes del océano Pacífico suroriental y, con ciertas salvedades, comparable a la sección ChilenoArgentina de la cordillera terrestre de Los Andes por
su extensión y altura. Nazca y Salas y Gómez son dos
cadenas secuenciales de montes que en conjunto tienen una extensión de 2.900 km (Naar et al., 2001) con
100 km de ancho en el caso de Salas y Gómez (Haase
et al., 1997) y 300 km en el caso de Nazca (Woods &
Okal, 1994). El cordón de Salas y Gómez se dispone
en dirección oeste-este y se localiza entre los paralelos
23°42’ y 29°12’S y meridianos 111°30’ y 86°30’W.
En su extremo occidental intercepta la dorsal del Pacífico este al interior de la Zona Económica Exclusiva
(ZEE) de Chile generada por la isla de Pascua y, en su
extremo oriental, se confunde con el extremo occidental del cordón submarino de Nazca. El cordón de Nazca se extiende en dirección suroeste-noreste y se localiza entre los paralelos 15°00’ y 26°09’S y los meridianos 86°30’ y 76°06’W. Su extremo meridional está
comprendido en la ZEE de Chile generada por la isla
San Félix, mientras que su extremo septentrional se
atenúa frente a la costa peruana en la zona de subducción Perú-Chile (Fig. 2).
El área de ambos cordones cubre una extensión
cercana a 1,2 millones km2, lo cual representa aproximadamente el 5,04% de la alta mar en el área 87 de
FAO (24.713.142 km² acorde con Sea Around Us,
2008). Adicionalmente, contiene 144 montes (de los
cuales 51 están en aguas de la ZEE de Chile) con profundidades de su cima entre 0 y 2.700 m con un promedio de 893 m desde la superficie (Fig. 3a). La altura
de estos MS desde el piso oceánico varía entre 1.000
m y 3.420 m con un promedio de 2.156 m, siendo el
rango 2.000 m a 2.500 m el más frecuente (Fig. 3b).
Dichos montes representan cerca del 54% de los MS
en el océano Pacífico suroriental (Gálvez, 2006). La
configuración de las montañas submarinas, tanto de
Salas y Gómez como de Nazca, es variada y contempla desde pequeños montes de formas cónicas hasta
atolones, pasando por intrincados guyots o mesetas
(Fig. 3c), la mayoría de ellos de pequeño volúmenes
(Fig. 3d).
483
Los MS de Nazca y Salas y Gómez son de origen
volcánico, formados por el hotspot de Pascua (Naar et
al., 2002) hace más de 30 millones de años, y que se
encuentran alineadas debido al desplazamiento de la
placa de Nazca. Las únicas dos cimas que se elevan
por sobre el nivel del mar son la isla de Pascua y la
isla Salas y Gómez. Los MS “recientemente” formados son Umu (2,7-5,8 Ma) y Pukao (6,4-6,6 Ma),
mientras que los de mayor edad corresponden a cerca
de 34 Ma y se ubican en el extremo norte de la cordillera de Nazca (Earth Reference Data and Models,
2007). Para mayor claridad, debe notarse que en esta
sección el término hotspot es usado en su acepción
geológica; es decir, como un sector que ha experimentado volcanismo activo por periodos prolongados de
tiempo y que es estacionario en relación a las placas
tectónicas. El concepto de ‘hotspot’ biológico (referido al final de esta revisión), fue introducido por el Dr.
Norman Myers y, en ecología terrestre, denota una
región con una considerable reserva de biodiversidad
que adicionalmente está bajo alguna amenaza importante.
Figura 3. Frecuencia porcentual de MS de Nazca y Salas y Gómez según a) rangos de profundidad (m) de la cima, b)
altura del monte (m), c) tipo de monte, y d) volumen (km3) del monte. Gráficos a partir de 95 montes registrados (Fuente:
Earth Reference Data and Models, 2007).
Figure 3. Percentage frequency of Nazca and Salas y Gómez seamounts by a) summit depth range (m), b) seamount
height (m), c) seamount type, and d) seamount volume (km3). Graphs are based on 95 mapped seamounts (Source: Reference Data and Models, 2007).
484
Naar et al. (2002) confeccionaron mapas del área y
tomaron muestras geológicas para evaluar la estabilidad del hotspot en la cuenca del Pacífico. Adicionalmente, mediante de modelos de movimiento de placas,
testearon el modelo de convección de los mantos de
Steinberger & O’Connel (1998 fide Naar et al., 2002)
en el sentido de que el hotspot Hawaiano y el de Pascua están convergiendo a razón de 10 mm año-1.
Acorde con estos autores, en los 30 Ma de edad de la
cordillera de Nazca se predicen cerca de 600 km de
convergencia entre estos dos hotspots.
Por otro lado, Woods & Okal (1994) por medio de
mediciones de velocidad del modo fundamental de las
ondas de Rayleigh, a lo largo de las cordilleras de
Nazca y Salas y Gómez, plantean que Nazca y las
planicies de Tuamotu son imágenes reflejadas formadas por un hotspot coincidente con el centro de dispersión Farellón-Pacífico. Por otro lado, las mediciones
en Salas y Gómez indicarían para estos autores que
esta cadena fue formada como una zona de fractura
permeable y no como una simple ruta de un hotspot.
Otros modelos que han sido propuestos para el origen
del hotspot de Pascua y la cordillera de Salas y Gómez
son una línea caliente de manto (Bonatti et al., 1977),
una fractura de propagación (Clark & Dymond, 1977),
una dorsal oceánica incipiente (Mammerickx, 1981), y
la ubicación de la isla de Pascua sobre un canal de
pluma originado más al este cerca de la isla Salas y
Gómez (Schilling et al., 1985; O’Connor et al., 1995).
Los estudios de formación de las cordilleras submarinas de Nazca y Salas y Gómez no son concluyentes,
ya que básicamente se basan en modelos de dinámica
de placas y ondas, por lo que aún persiste un cierto
nivel de controversia respecto a la formación de estas
cadenas.
Características oceanográficas físicas
Varias características físicas de los MS, condiciones
de estratificación y características del flujo oceánico
son los elementos que interactúan para generar diferentes respuestas de dinámicas oceanográficas en los
MS. Entre estas se cuentan las columnas de Taylor, la
formación de domos de superficies de densidad, celdas de circulación cerradas y reforzamiento de mezclas verticales. Debido a las condiciones oceánicas de
variabilidad del flujo, es probable que las condiciones
locales en la dinámica de los MS y los procesos de
interacción biofísica resultantes también sean variables. Esto hace difícil la cuantificación de una respuesta “idealizada” de un particular monte submarino a las
interrupciones del régimen de flujos oceánicos. Es
ampliamente aceptado que la dinámica de los MS
genera condiciones que incrementan los flujos verticales de nutrientes y retención de materia orgánica, sus-
tentando la productividad que alimenta a los niveles
tróficos superiores. A la fecha, sin embargo, ha habido
muy poca evidencia concreta y consistente que sustente estas aseveraciones. Esto probablemente es debido a
las condiciones inestables de las características oceánicas forzantes, las que no permiten una respuesta
“idealizada” como las columnas de Taylor y las celdas
de circulación cerrada. Adicionalmente, los MS pueden verter pasivamente trazas tales como flujos de
clorofila, proveyendo así una fuente de parches biofísicos en el océano circundante. Tal variabilidad impone un interesante desafío no solo para oceanógrafos,
sino que también para el manejo de los MS (White &
Mohn, 2002; White et al., 2007).
A excepción de las investigaciones realizadas por
las expediciones soviéticas ya mencionadas, no se
dispone de otros estudios oceanográficos específicos
que analicen la particular dinámica sobre los MS de
Nazca y Salas y Gómez. No obstante, esto no implica
que no se hayan tomado muestras oceanográficas (y
paleoceanograficas (Shipboard Scientific Party, 2003))
en el área. Así por ejemplo, en mayo de 1994 se efectuaron mediciones en torno a isla de Pascua para realizar estudios hidrográficos y de circulación geostrófica
(Moraga et al., 1999); en junio de 1995 la nave de
investigación “Sonne” colectó muestras de temperatura y salinidad en la columna de agua del área de Nazca
(Daneri et al., 2000). Igualmente, en el marco del
programa Cimar 5 Islas Oceánicas de la Armada de
Chile, en octubre de 1999 se efectuaron 32 estaciones
oceanográficas entre Caldera (27°00’S, 71°46’W) e
isla de Pascua (27°00’S, 107°35’W), donde se realizaron registros continuos de temperatura, salinidad y
oxígeno en la columna de agua entre la superficie y
los 2.500 m de profundidad (Fuenzalida et al., 2007;
Rivera & Mujica, 2004). Dicho transecto cubre algunos montes de la cordillera de Salas y Gómez entre la
longitud 100°28’W e isla de Pascua (Fig. 2). Finalmente, durante 2003 y 2005 se efectuaron muestreos
oceanográficos (temperatura, salinidad y oxígeno) en
la columna de agua hasta 240 m de profundidad en el
área de Nazca, en el marco de un proyecto de caracterización de la zona como área de crianza del pez espada Xiphias gladius (Yáñez et al., 2004, 2006).
Sin duda que todos los estudios mencionados fueron diseñados con objetivos diferentes. No obstante,
éstos guardan una estrecha relación debido a las técnicas de muestreo empleadas y a las variables medidas.
En atención a lo anterior, se debiera realizar el esfuerzo de compilar dichos datos en una base común, para
evaluar la factibilidad de desarrollar análisis que den
cuenta de la dinámica oceánica de las masas de agua
asociadas a los MS de las cordilleras de Nazca y Salas
y Gómez.
Características oceanográficas biológicas
La biomasa de peces y otros zooplanctívoros es
usualmente alta sobre MS someros, intermedios, y a
veces, sobre los de gran profundidad. Esto no puede
ser explicado en términos de control ‘bottom up’, el
cual es impulsado por procesos de surgencia local y el
resultante aumento de la producción primaria. Aunque
procesos de surgencia ocasionalmente ocurren, éstos
raramente penetran la capa fótica y no se ha observado
que permanezcan lo suficiente sobre los MS como
para afectar el crecimiento de las poblaciones locales
de zooplancton. De hecho la biomasa zooplanctónica
de los MS es menor sobre la cima de los mismos que
en las aguas circundantes, especialmente en los MS
someros (Koslow, 2007). El peso de la evidencia disponible indica que el enriquecimiento trófico sobre los
MS se debe a contribuciones vía: (i) retención en el
fondo del zooplancton migrante verticalmente, y (ii)
flujos horizontales potenciados de alimento (partículas) suspendido. La retención en el fondo del zooplancton migrante, temprano en la mañana, es el mayor mecanismo para la acumulación y focalización
trófica sobre los MS, particularmente los de profundidades someras e intermedias. Los flujos horizontales
potenciados de presas planctónicas emergen para ser
una de las vías principales de aportes tróficos sobre los
MS profundos (Clark et al., 2004). Aparentemente, los
fuertes flujos se mantienen debido a un sustantivo
potenciamiento de las corrientes y a la amplificación
de las ondas internas sobre la topografía de los MS.
Las interacciones biofísicas son los mecanismos claves responsables para la mantención de las altas biomasas en niveles tróficos elevados. En consecuencia,
el enriquecimiento biológico de los MS puede ser
producto de un bombeo desde el fondo hacia arriba,
impulsando por un subsidio trófico a los carnívoros,
en vez de un enriquecimiento local de la producción
primaria (Genin & Dower, 2007).
Al igual que los estudios de oceanografía física,
también son escasos los estudios disponibles de oceanografía biológica relativos a los MS de Nazca y Salas
y Gómez. A pesar de esto, se cuenta con algunos análisis de datos tomados en el área, que corroboran que
las aguas circundantes a los MS de Nazca y Salas y
Gómez albergan una gran cantidad y diversidad de
larvas; mientras que otros estiman tasas de producción
primaria más elevadas que para el océano circundante.
Así por ejemplo, Daneri et al. (2000) en un estudio de
producción primaria en el Sistema de la Corriente de
Humboldt y áreas oceánicas asociadas frente a Chile,
indican bajos valores de producción primaria neta en
el área oceánica frente al norte de Chile (0,7 ± 0,4 μg
C l-1 h-1), pero notan que este índice mejora levemente
en el área de la cordillera de Nazca (1,8 ± 1,2 μg C l-1
485
h-1). Por otro lado, Rivera & Mujica (2004) indican
que el índice de diversidad de larvas de decápodos es
notablemente alto en estaciones de muestreo cercanas
a los MS de Nazca, si se compara con el mismo índice
donde no hay asociaciones con MS. Adicionalmente,
en dicha estación de muestreo estos autores registraron
un phyllosoma de Scyllarus delfini (Scyllaridae) y
larvas de carideos de los géneros Oplophorus, Nematocarcinus, Periclimenes y Lysmata, los que cuentan
con especies endémicas en los MS y en sus islas asociadas, corroborando así que esta alta diversidad está
estrechamente relacionada con dichos montes.
Adicionalmente, durante 2003 y en la zona de la
cordillera de Nazca, Yáñez et al. (2004) realizaron 14
lances de arrastre con una red IKMT para tomar muestras de micronecton superficial entre 5 y 70 m durante
la medianoche. Los resultados obtenidos fueron analizados en la perspectiva de su relación con la dieta del
pez espada, por lo que no se dispone de análisis que
vinculen los resultados con la dinámica de los MS o
las especies adultas que habitan los mismos.
Finalmente, en el marco de los ya mencionados
cruceros de investigación de la flota rusa, se tomaron
múltiples muestras ictioplanctónicas en el área. Lamentablemente, los resultados de estas investigaciones
están publicados en ruso (Belayanina, 1989, 1990), y
hay pocas referencias a estos estudios en la literatura
internacional.
DESCRIPCIÓN BIOLÓGICA DE NAZCA Y
SALAS Y GÓMEZ
El estudio faunístico de las cordilleras submarinas del
Pacífico suroriental comenzó en la década de 1950,
pero las investigaciones más detalladas fueron hechas
entre 1973 y 1987 durante varios cruceros de naves de
investigación rusas, particularmente de los B/I "Ikhtiandr", "Professor Mesyatzev" y "Professor Shtokman". Una compilación de los resultados de estas
investigaciones sobre las cordilleras submarinas de
Nazca y Salas y Gómez fue efectuada por Parin et al.
(1997) y actualizada por Mironov et al. (2006); en
tanto que una comprehensiva base de datos con las
especies identificadas por localidad de muestreo puede
ser obtenida desde el sitio web de SeamountOnline
(2007). Un resumen de los resultados de estos trabajos
se muestra a continuación.
Composición y distribución de especies
En los 23 MS muestreados de las cordilleras de Nazca
y Salas y Gómez (Fig. 2) se identificaron 208 géneros
y 226 especies de invertebrados bentónicos y bentopelágicos; en tanto que 131 géneros y 170 especies de
486
peces también fueron identificadas (Tabla 1). Siete
géneros y 150 especies fueron descritas por primera
vez: cuatro y 74 en invertebrados, tres y 76 en peces.
Las comunidades de invertebrados de fondo en las
cimas de los montes se caracterizan por la fuerte dominancia de pocas especies. A profundidades menores
de 400 m la langosta enana (Projasus bahamondei) es
dominante al este de los 83°W, mientras que los erizos
predominan al oeste. En varias combinaciones y a
grandes profundidades son más abundantes las esponjas, gorgónidos, estrellas de mar y camarones. El jurel
(Trachurus symmetricus murphyi), usualmente domina
las comunidades de peces bentopelágicas sobre los
montes hacia el este de los 85°W. Otras especies
abundantes son Emmelichthys cyanescens, E. elongatus, Decapterus muroadsi, Zenopsis oblongus, Epigonus elegans y Pentaceros quinquespinis, todas las
cuales forman la base de pesquerías comerciales. Entre
los peces se destaca la dominancia de Caelorinchus
immaculatus (cordillera de Nazca) y Pterygotrigla
picta. La mayor diversidad de peces se estimó a profundidades de entre 500 y 600 m; en tanto que los
biotipos de comunidades de fondos blandos y rocosos
difieren significativamente.
Relaciones faunísticas y endemismo
La fauna bentónica y bentopelágica de invertebrados y
peces del área está mucho más relacionada con el
Pacífico Indoccidental antes que con el Pacífico oriental (Fig. 4). Así por ejemplo, el mayor grado de afinidad es con el sur de Japón (85%), seguido del sureste
de Australia (77%) y de Hawai (74%). De las especies
registradas en Nazca y Salas y Gómez, 24 también han
sido reportadas para otras regiones como Hawai (16
spp.), sur de Japón (11 spp.), Nueva Caledonia (5
spp.), Filipinas (5 spp.) y Australia (4 spp.). En el área
es posible encontrar mayores niveles de similitud
faunística entre algunos montes cuando se analizan los
invertebrados, pero igualmente hay montes “vecinos”
que son notablemente diferentes en su composición
faunística en base a invertebrados.
Las cordilleras de Nazca y Salas y Gómez en conjunto presentan tasas de endemismo de 41,2% para
peces y de 46,3% para invertebrados que viven en el
fondo (Parin et al., 1997; Mironov et al., 2006) con
adiciones). Estas tasas de endemismo son las más altas
encontradas en MS, e incluso superan a las de ecosistemas asociados a ventanas hidrotermales, uno de los
hábitat más aislados e inusuales del océano (Richer de
Forges et al., 2000). Considerando la fauna de invertebrados, Parin et al. (1997) postulan la provincia
biogeográfica Salas y Gomesian entre 83ºW y 101ºW,
mientras que de acuerdo a la fauna íctica, postulan la
provincia biogeográfica Nazcaplatensis, que incluye
las cordilleras de Salas y Gómez, la de Nazca y posiblemente el sublitoral y batial superior de las zonas de
islas Desventuradas, archipiélago de Juan Fernández,
e islas Salas y Gómez y Pascua.
En cuanto a los invertebrados que habitan en esta
zona es posible indicar que se han reportado 76 especies endémicas, y a nivel de género se han reportado
dos endémicos (Pseudoplectella y Cribrosoconcha).
Destacan en esta zona 25 especies del orden Scleractinia (corales pétreos formadores de arrecifes), de las
cuales una especie es endémica, así como 25 especies
del grupo de los gastrópodos Turridae de los cuales el
96% son endémicos (Tabla 2).
Tabla 1. Familias, géneros y especies de invertebrados y peces registrados en Nazca y Salas y Gómez (Mironov et al.,
2006).
Table 1. Invertebrate and fish families, genera, and species registered in Nazca and Salas y Gómez (Mironov et al., 2006).
Peces
Invertebrados
Géneros de invertebrados reportados (total)
Géneros de invertebrados donde el número
de especies es conocido
Número de géneros de invertebrados representados por una especie
Número de géneros de invertebrados representados por más de tres especies
Familias de peces reportadas
Géneros de peces reportados (número de
especies)
Número de géneros de peces representados
por una especie
Parin et al. (1997)
Mironov et al. (2006)
177
143
(192 spp.)
117
(82%)
208
180
(226 spp.)
142
(79%)
4
3
64
128
(171 spp.)
106
(83%)
64
131
(170 spp.)
109
(83%)
487
CORALES DE AGUAS FRÍAS
Figura 4. Géneros de peces en la fauna de las cordilleras
de Nazca y Salas y Gómez (bajo 800 m de profundidad)
que ocurren en otras regiones. Fuente: Parin et al. (1997)
y Mironov et al. (2006).
Figure 4. Fish genera in Nazca and Salas y Gómez (under 800 m depth) occurring in other regions. Source:
Parin et al. (1997) and Mironov et al. (2006).
En cuanto a la fauna íctica que habita esta zona, es
posible indicar que se han registrado 70 especies endémicas, de las cuales cinco especies (Mollisquama
parini, Facciolella castlei, Gaidropsarus parini, Caelorinchus immaculatus, Plagiogeneion geminatus),
sólo se encuentran al este del meridiano 83ºW, o límite de la provincia biogeográfica Salas y Gomesian. La
mayoría de las especies endémicas pertenecen a Macrouridae (9 spp.) y Moriidae (6 spp.), mientras que
las familias representadas sólo por especies endémicas
son: Torpedinidae, Ophichthidae, Nettastomatidae,
Congridae, Argentinidae, Photichthyidae, Sternoptychidae, Aulopidae, Gadidae, Chaunacidae, Ogcocephalidae, Polymixiidae, Pentacerotidae, Percophidae.
Supuestamente existirían tres géneros endémicos:
Mollisquama (Squalidae), Anatolantias (Serranidae) y
Dactylopsaron (Percophidae).
Según Parin et al. (1997) la composición faunística
de los principales animales de las cordilleras de Nazca
y Salas y Gómez puede ser explicada principalmente
por dos procesos: una dispersión hacia el este de la
fauna del Pacífico oeste y una activa especificación in
situ. Estas dos hipótesis aún esperan ser comprobadas.
Antecedentes generales
Aunque su existencia ha sido conocida por siglos, la
observación y estudio del hábitat de corales de aguas
frías en su medio natural comenzó sólo en la década
pasada, cuando se comenzó a usar instrumental sofisticado para explorar los ambientes de aguas profundas.
El uso de estas tecnologías modernas, ha cambiado el
paradigma convencional que los corales están confinados a regiones tropicales y subtropicales de aguas
someras y cálidas. Los científicos han sido capaces de
explorar una variedad de ecosistemas de coral avanzando en profundidad, oscuridad y aguas frías, particularmente en las altas latitudes (Koslow, 2007). Algunos de estos corales de aguas frías construyen bancos o arrecifes tan complejos como los de sus parientes tropicales. Mediante técnicas de datación radioactiva se sabe que algunos bancos y arrecifes vivos tienen 8.000 años de edad, y se cree que otros podrían
llegar a 50.000 años (Roberts, 2007). Registros geológicos indican que los arrecifes de coral de aguas frías
han existido por millones de años.
Los sistemas de coral de aguas frías pueden ser encontrados en casi todos los mares y océanos del mundo: en fiordos, a lo largo del talud continental, y alrededor de bancos y MS alejados de la costa. Al vivir
sin luz y en un ambiente relativamente rico en nutrientes, los ecosistemas de coral de aguas frías funcionan
en una forma muy diferente a los sistemas de coral de
aguas someras. Los corales de aguas frías, viviendo a
profundidades en que no llega la luz, para su alimentación no disponen de algas simbióticas con dependencia lumínica; y por lo tanto, dependen del suministro de materia orgánica particulada transportada por
las corrientes y del zooplancton. Para capturar su alimento en forma eficiente, muchos de estos corales
producen una estructura ramificada tipo árbol, para
soportar las colonias de pólipos que comparten un
esqueleto común de carbonato de calcio. Estas estructuras forman un complejo hábitat tridimensional que
proporciona una multitud de micro-nichos para la
comunidad animal asociada (Freiwald, 2002; ver artículos en Freiwald & Roberts, 2005).
Los arrecifes más espectaculares están construidos
por corales pétreos, a profundidades de varios cientos
de metros. Estos corales pétreos forman colonias que
presentan grandes variaciones en tamaño, desde pequeñas y esparcidas colonias de no más de unos pocos
metros de diámetro, hasta vastos y complejos arrecifes
que miden varias decenas de kilómetros (e.g., arrecife
de Lophelia de Mar de Røst al norte de Noruega cubre
488
Tabla 2. Endemismo de los grupos de invertebrados encontrados en los MS de la Cordillera de Nazca y Salas y Gómez
(Fuente: Mironov et al., 2006).
Table 2. Endemism of invertebrates in the Nazca and Salas y Gómez seamount ridges (Source: Mironov et al., 2006).
Grupos
Nombre común
Hyalospongiae
Scleractinia
Gastropoda Turridae
Cirripedia
Tanaidacea
Macrura
Brachiura & Anomura
Bivalvia Septibranchia
Brachiopoda
Echinoidea
Esponjas de cristal
Corales pétreos
Caracoles
Crustáceos cirripedios
Crustáceos
Crustáceos decápodos
Crustáceos decápodos
Bivalvos
Braquiópodos
Erizos
Total
100 km2 y algunas partes alcanzan 30 m desde el fondo marino). Estos arrecifes de coral de aguas frías
están construidos por sólo algunas especies. Según
Turley et al. (2007) sólo seis de las 700 especies conocidas forman arrecifes. En el Atlántico Norte, el
Mar Mediterráneo y el Golfo de México, Lophelia
pertusa y Madrepora oculata son los más abundantes
constructores de arrecifes. En el talud continental de
Florida y Carolina del Norte los arrecifes están principalmente construidos por Oculina varicosa. En el
hemisferio sur, en los montes y bancos submarinos de
Tasmania y Nueva Zelanda, Goniocorella dumosa y
Solenosmilia variabilis son las especies más prominentes (Koslow, 2007).
Los ecosistemas de corales de aguas frías no son
dominio exclusivo de los corales pétreos. El Pacífico
norte, por ejemplo, es conocido por poseer fabulosos
ejemplos de ecosistemas de los llamados jardines de
octocorales, que están entre los más ricos y notablemente coloridas comunidades encontradas en aguas
profundas en altas latitudes. Sólo recientemente se ha
comenzado a entender algunas de las complejidades
de estos ocultos ecosistemas de corales de aguas frías.
Así como sus contrapartes, los corales de aguas frías
son refugio para miles de otras especies, en particular
esponjas, poliquetos, crustáceos, moluscos, equinodermos, briozoos y peces comerciales (Rogers, 1999;
Fosså et al., 2002; Husebø et al., 2002).
Descubrimientos recientes están cambiando el conocimiento acerca del proceso de formación de arrecifes y donde ellos ocurren. Los investigadores están
comenzando a entender que los arrecifes de aguas frías
pertenecen a un continuo, donde en un extremo, la
evolución de la simbiosis dependiente de la luz
hapermitido a los corales sobrevivir bajo pobres regí-
Nº de especies
Endémicas
6
25
25
14
9
29
24
7
4
19
2 (33%)
1 (4%)
24 (96%)
11 (79%)
2 (22%)
10 (34%)
10 (41%)
7 (72%)
1 (25%)
8 (42%)
164
76 (46,3%)
menes nutricionales en aguas someras tropicales, y por
el otro extremo, una oferta suficiente de alimento
permite a los corales prosperar como organismos carnívoros en aguas profundas y frías.
Especies en Nazca y Salas y Gómez
De los estudios de Parin et al. (1997) y Mironov et al.
(2006), destacan en esta zona 25 especies de la subclase Zoantharia (Hexacorales) orden Scleractinia (corales pétreos formadores de arrecifes, Tabla 3), de las
cuales una especie es endémica de la zona (Tabla 2).
De estas especies, Desmophyllum dianthus de la familia Caryophylliidae junto con Madrepora oculata de la
familia Oculinidae (Fig. 6 en Gálvez, 2007) son las
dos especies para las cuales se dispone de mayor información biológica.
Desmophyllum dianthus es una especie cosmopolita y ha sido descrita para un amplio rango de profundidades (25-2.460 m) en la costa de Chile (cordón de
Nazca, Archipiélago de Juan Fernández, cercanías de
Chiloé y Magallanes). Esta especie también se ha
encontrado en los fiordos australes, y puede crecer
hasta 40 cm y vivir en aguas someras de hasta 8 m de
profundidad, registrándose grandes agregaciones bajo
20 m (Försterra et al., 2005). Los grandes bancos de
más de 1.500 especímenes por m2 están generalmente
restringidos a murallones verticales, creciendo los
ejemplares hacia abajo, lo cual puede indicar sensorialidad a la sedimentación. Observaciones submarinas
han detectado altas concentraciones de Desmophyllum
dianthus a profundidades superiores a 250 m, los corales presentan una cubierta café que probablemente se
deba a componentes de hierro/manganeso, lo que indicaría condiciones de anoxia.
489
Tabla 3. Familias y especies de antipatarios y escleractinias en la cordillera de Nazca y Salas y Gómez (Fuente: SeamountOnline, 2007, *Molodtsova, 2005).
Table 3. Families and species of antipatharia and scleractinia in Nazca and Salas y Gómez (Source: SeamountOnline,
2007, *Molodtsova, 2005).
Familia
Antipathidae
Caryophylliidae
Dendrophylliidae
Flabellidae
Fungiacyathidae
Guyniidae
Oculinidae
Turbinoliidae
Género
Antipathes*
Bathypathes
Cirripathes
Caryophyllia
Conotrochus
Crispatotrochus
Deltocyathus
Desmophyllum
Paracyathus
Dendrophyllia
Enallopsammia
Flabellum
Javania
Polymyces
Fungiacyathus
Stenocyathus
Madrepora
Idiotrochus
Peponocyathus
Especie
calveri, C. diomedea, C. perculta, C. rugosa, C. solida
funicolumna
galapagensis
andamanicus, D. stelluatus, D. vaughani
dianthus
humilis
gracilis
rostrata
apertum
cailleti
wellsi
paliferus, F. pliciseptus, F. stephanus
vermiformis
oculata
kikutii
australiensis, P. orientalis
Madrepora es un género cosmopolita que ha desarrollado varias especies y dos de ellas, Madrepora oculata y M. carolina, están frecuentemente asociadas con
arrecifes de coral de aguas frías. Las ramificaciones de
las colonias de Madrepora generalmente son mucho
más frágiles que las de Lophelia y tienden a quebrarse
fácilmente, lo que limita considerablemente su capacidad para construir armazones. Incluso en áreas donde
Madrepora domina la comunidad coralina no se encuentran gruesos armazones de arrecifes. Es muy frecuente que Madrepora construya arrecifes en asociación con otras especies, como L. pertusa y Goniocorella dumosa. Sin embargo, muchos aspectos biológicos
y ecológicos aun permanecen no estudiados en relación a estos sistemas de arrecifes de coral de aguas
frías.
En el Pacífico suroriental Madrepora oculata ha
sido identificada para las zonas de Nazca (MS Dorofeev, Ichthyandr y Ecliptic), Salas y Gómez (MS Cupole), en la zona sur austral (islas Diego Ramírez,
Paso Drake, SSW isla Hornos) y en las cercanías de
Valdivia. Para el Pacífico suroriental, M. oculata se ha
registrado a profundidades de 59 m (SSW Isla Hornos) a 2.500 m (Valdivia) (SUBPESCA, 2005).
Finalmente, Glynn & Ault (2000) informan del
hallazgo de cuatro géneros de corales fósiles (Stylophora, Pocillopora, Leptoseris, Porites, todos corales
de aguas someras tropicales y subtropicales) en el área
de Nazca. Particularmente, las muestras fueron tomadas en estudios geológicos desde el monte submarino
“Shoal Guyot” entre 205 y 227 m de profundidad
(Allison et al., 1967 fide Glynn & Ault, 2000). Adicionalmente, es conocido que especies de los géneros
Pocillopora y Porites son frecuentes en isla de Pascua,
lo que para estos autores reafirma el estrecho lazo
biogeográfico entre las regiones del Indo-Pacífico y
Pacífico suroriental.
PRÁCTICAS PESQUERAS EN NAZCA Y SALAS
Y GÓMEZ
Tecnologías de captura
De acuerdo con Mirnov et al. (2006), los artes de pesca utilizados por las expediciones científicas rusas y
soviéticas que realizaron capturas en el área entre
1973 y 1987, consistieron en redes de arrastre de fondo y media agua, palangres verticales y de fondo y
490
trampas con carnada. En 1998 el área de Nazca también fue explorada por una expedición científica chilena, cuyo objetivo era la prospección de agregaciones
de orange roughy (Hoplostethus atlanticus) con red de
arrastre de fondo modelo Arrow, similar a las actualmente utilizadas en la captura de esta especie en aguas
jurisdiccionales de Chile (Lillo et al., 1999).
También se han documentado actividades ocasionales de pesca comercial, efectuadas en el área de
Nazca por naves de compañías chilenas y naves rusas.
Estas actividades han estado orientadas principalmente
hacia la captura de langosta enana (Projasus bahamondei) y secundariamente hacia cangrejo dorado
(Chaceon chilensis), usando líneas de trampas y carnada (Arana & Venturini, 1991; Weinborn et al.,
1992; Arana, 2003). Las actividades comerciales de
captura de alfonsino (Beryx splendens) en el área de
Nazca, aun cuando han sido esporádicas, son más
persistentes en el tiempo que las sobre langosta enana,
así por ejemplo se ha documentado la captura de este
pez por parte de flota chilena con redes de arrastre en
1998, 2002-2003 y 2005 (ver Anuarios Estadísticos de
Pesca del Servicio Nacional de Pesca de Chile).
No se conoce de información pública – para el área
– de actividades de pesca comercial de fondo o demersal por parte de naves de otras naciones, aun cuando
Arana (2003) indica que en 1991 y 1992 se hizo evidente la presencia de naves de distintas banderas en la
zona. A pesar de esto, para el Pacífico suroriental
(área 97 de FAO) se destacan algunos registros de
captura en las bases estadísticas de FAO (2007), los
que deben ser investigados en mayor detalle ya que
son indicativos de probables actividades de pesca de
fondo en el área. Prueba de ello son las capturas de
orange roughy informadas por China entre 2001 y
2007, y las informadas por Korea entre 1999 y 2006
(Anon., 2008).
A pesar de la escasa información disponible de actividades comerciales, se destaca que el área de los
MS de Nazca y Salas y Gómez ha permitido la operación de artes de pesca de fondo de variados tipos. A
partir de la información disponible para la flota chilena es posible indicar que las redes de arrastre utilizadas han sido de dos tipos: modelo Arrow para pesca
de fondo (Lillo et al., 1999) y de cuatro paneles para
pesca de alfonsino (SUBPESCA, 2006). Si bien el
primer arte es operado, en cierto trayecto del lance, en
contacto con el fondo marino, mientras que el segundo
es desplegado sobre el fondo, ambos están diseñados
para resistir impactos con el piso oceánico.
Historia pesquera y capturas
Es difícil acceder a registros fidedignos de capturas
registradas en las zonas de Nazca y Salas y Gómez.
Esto se debe a que usualmente los registros son oficialmente informados como efectuados en aguas internacionales y, en el mejor de los casos, se indica
solamente el número clasificatorio de la macrozona
FAO (área 87). Cuando se ha podido acceder a las
bitácoras de pesca, ha sido posible tener certeza que
las capturas fueron efectuadas en la zona bajo análisis,
mientras que en otros casos, solamente se ha inferido
que las capturas fueron efectuadas en la zona por los
tipos de especies capturados. Dejando a parte aquellas
especies pelágicas o altamente migratorias como la
jibia (Dosidicus gigas), caballa (Scomber japonicus),
jurel, reineta (Brama brama) y túnidos en general, se
presenta una estimación de las capturas efectuadas en
el área para cuatro especies de fondo de interés comercial (Tabla 4).
IMPACTOS DE LA PESCA
En el área no se han desarrollado estudios directos o
indirectos orientados a determinar el impacto causado
por actividades de pesca. Debido a lo anterior, la presente sección proporciona una perspectiva general
respecto a este tópico. No obstante, se debe notar que
Parin et al. (1997) indican que ramas de gorgónidos de
hasta 1,7 m de altura fueron extraídas en el área por
redes de arrastre de fondo. Más aun, estos mismos
autores observan que “cambios significativos se notaron entre 1979-1980 y 1987 en la estructura de las
comunidades del fondo. Los antipatarios fueron destruidos por el arrastre de fondo…, y [los cirripedios]
se perdieron con su sustrato animal, [mientras] que las
poblaciones de erizo… declinaron después de la destrucción” (Parin et al., 1997). Los eventos descritos
son prueba de la fragilidad del ecosistema asociado a
los montes submarinos de Nazca y Salas y Gómez.
La recientemente acordada Guía Internacional de
FAO para el Manejo de las Pesquerías de Aguas Profundas en la Alta Mar (FAO, 2008) distingue dos categorías de impactos adversos en ecosistemas de aguas
profundas, sobre la estructura del ecosistema o sobre
la función del mismo. Estas categorías serán brevemente descritas bajo los subtítulos de deterioro del
hábitat e impactos ecosistémicos, respectivamente.
Deterioro del hábitat
Por deterioro del hábitat se entiende el “daño a las
estructuras vivas del fondo marino (e.g., corales, esponjas, plantas marinas), así como la alteración de las
estructuras geológicas (e.g., rocas, guijarros, grava,
tierra y fango), que sirven como área de crianza, refugio y sustento para peces y organismos vivos del – o
en estrecha relación con – el fondo” (Morgan &
Chuenpagdee, 2003). Para el caso de áreas tales como
491
Tabla 4. Estimaciones de captura (toneladas), para cuatro especies comerciales, por año en la zona de las cordilleras
submarinas de Nazca y Salas y Gómez (Fuente: FAO (2007), Anon. (2008) y Servicio Nacional de Pesca).
Table 4. Estimated catch (tons) for four commercial species, by year, in Nazca and Salas y Gómez (FAO, 2007; Anon.,
2008; Fishery Statistic Yearbooks of National Fisheries Service, Chile).
1979
1980
1981
1982
1983
1984
1988
1989
1991
1992
1998
1999
2000
907
-
12
-
676
-
620
-
633
-
458
-
98
36
-
-
144
-
-
-
Projasus bahamondei
-
8
4
-
-
-
-
-
(*)
(*)
22
5
Zeus faber
-
-
-
-
-
-
-
-
-
-
5
-
2001
2002
2003
2005
-
2
-
11
-
5
-
(a)
Beryx spp.
Emmelichthyidae
(a)
Beryx spp.
Emmelichthyidae
Projasus bahamondei
1
-
-
-
Zeus faber
-
-
-
-
-
(*) Se conoce que se efectuaron capturas en estos años por parte de naves chilenas.
(a) Principalmente Beryx splendens. Desde 1998 las capturas corresponden a flota
chilena exclusivamente
los MS, que tienen altos niveles de endemismo, la
utilización de artes de arrastre de fondo podría erradicar especies antes de que se conozca su existencia
(Koslow et al., 2001). De acuerdo con Rogers (2004),
“en los MS, los impactos humanos sobre corales de
aguas frías han sido causados casi exclusivamente por
actividades pesqueras” y “el impacto de portalones
que pesan varias toneladas, cadenas y otras partes del
arte de pesca aplastan y quiebran las estructuras de
coral, reduciendo el hábitat coralino o removiéndolo
completamente”. Las redes de arrastre para operar en
MS son diseñadas con relingas inferiores de gran peso
(compuestas de cadenas y bobinas) y portalones altamente resistentes al impacto. Además dichas redes
poseen bajas alturas de despliegue vertical de la boca.
Estas configuraciones se toman como ‘cautelas’ o
resguardos para ayudar al capitán a evitar trabas de la
red con el fondo.
En el caso de otros artes de pesca como líneas de
trampas y espineles, se considera que su impacto en el
hábitat de fondo es de menor envergadura (Morgan &
Chuenpagdee, 2003). No obstante, se ha documentado
la captura de corales antipatarios en pesca de bacalao
de profundidad con trampas (P. Arana, com. pers.) los
que han sido depositados en la colección coralina de la
Universidad Austral de Chile. Además se dispone de
varias evidencias de captura de corales antipatarios y
madreporarios en la pesquería de bacalao de profundidad con espineles (A. Bravo, com. pers.), los que se
encuentran disponibles en la misma colección. Por lo
tanto, el impacto negativo sobre los corales de aguas
frías, por parte de artes de pesca de fondo, puede ser
similar o mayor dependiendo de la intensidad de las
operaciones de pesca que se desarrollen. En una escala
de 1 a 5, siendo el valor máximo el de mayor impacto
en el hábitat, Morgan & Chuenpagdee (2003) califican
con nivel 5 el impacto físico y biológico de dragas y
redes de arrastre de fondo sobre el hábitat; las redes de
enmalle y trampas de fondo son calificadas con nivel 3
(impacto físico sobre el hábitat) y 2 (impacto biológico sobre el hábitat); mientras que los espineles de
fondo son calificados con nivel 2 en ambos casos.
Se ha argumentado que los impactos sobre el hábitat son específicos y dependen del tipo de arte de pesca, la temporada en que se desarrolle el estudio a los
tipos de comunidades biológicas en el área bajo análisis, entre otros factores. Un reciente proyecto de investigación nacional, en desarrollo por la Pontificia
Universidad Católica de Valparaíso, debiera proporcionar una idea más precisa de los impactos de ciertos
artes de pesca en fondos marinos chilenos (particularmente MS), toda vez que su objetivo principal es “recopilar, sistematizar e incrementar el conocimiento
existente sobre la distribución geográfica, biodiversidad e impacto pesquero, de los MS en la ZEE de Chile” (Yañez et al., 2008).
Impactos ecosistémicos
Los probables impactos ecosistémicos de pesquerías
de arrastre de aguas profundas pueden ser caracterizados en dos sentidos. Primero, los impactos sobre las
relaciones predador-presa, la trama trófica y otros
impactos relacionados con la remoción de grandes
cantidades de especies objetivos y especies de la fauna
acompañante del ecosistema en el cual las mismas
juegan un rol particular. Segundo, el impacto físico de
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la pesca sobre el fondo oceánico, en particular sobre
corales, esponjas y otros organismos estrechamente
vinculados al fondo marino y que conforman grupos
de especies claves, ya que configuran la estructura
básica del ecosistema bentónico donde estas pesquerías ocurren (Gianni, 2004).
Desafortunadamente, existe una gran falta de información en relación con el primero de los dos tipos
de impactos. De acuerdo con Butler et al. (2001), el
efecto de la remoción de gran número de predadores
tope en ecosistemas de profundidad es escasamente
conocido. Koslow et al. (2000) indican que las dudas
más importantes son en relación a las implicancias
ecológicas de largo plazo en el agotamiento de especies de nivel trófico medio-alto en ecosistemas de
aguas profundas y el impacto sobre las poblaciones de
predadores y presas, y que para estos cuestionamientos actualmente hay pocas respuestas. No obstante,
recientes estudios (Morato et al., 2004, 2006), basados
en la historia de vida y las características ecológicas
de las poblaciones que tradicionalmente habitan los
MS, probaron la hipótesis que las poblaciones de peces de los MS generalmente tienen un mayor nivel de
vulnerabilidad a la pesca, y que esta vulnerabilidad
está correlacionada con sus parámetros poblacionales.
Adicionalmente, determinaron que los resultados son
similares cuando se consideran solamente especies
comercialmente explotadas. Las características biológicas ligadas a una alta vulnerabilidad incluyen alta
longevidad, maduración sexual tardía, bajas tasas de
crecimiento y mortalidad natural. A partir de estos
resultados, los autores concluyen que la pesca sobre
MS tiende a ser no sustentable, dados los actuales
niveles de explotación y las técnicas de captura. A
igual conclusión llegan Johnston & Santillo (2004),
luego de una revisión de la literatura internacional
sobre el tema.
En relación al segundo tipo de impacto ecosistémico, existe real preocupación por parte de la comunidad
científica internacional en relación al efecto del arrastre de fondo sobre hábitat de aguas profundas, en particular sobre corales y otras especies sésiles como
esponjas, las que forman la estructura base de ecosistemas biológicamente diversos de aguas profundas. De
acuerdo con Rogers (2004) “las pesquerías nuevas de
aguas profundas han sido a menudo caracterizadas por
grandes cantidades de coral como fauna acompañante
en los primeros años, y éstos han declinado en la medida que el hábitat de coral ha sido alterado”. Como ya
se ha dicho, los corales de aguas profundas crecen
lentamente y los arrecifes toman miles de años en
desarrollarse; incluso hay evidencias que el reclutamiento de las larvas de coral es esporádico. Adicionalmente, estudios genéticos y reproductivos sugieren
que en áreas donde los corales de aguas profundas son
impactados por la pesca, las colonias pueden ser reducidas a pequeños parches donde la reproducción
sexual no es viable (Le Goff-Vitry et al. fide Rogers,
2004). Dados estos factores, la recuperación de corales
de aguas profundas, de impactos significativos de
actividades de arrastre, es probable que sea extremadamente lenta, y donde el hábitat es completamente
alterado puede que dicha recuperación nunca ocurra.
Dado que dichos arrecifes son también el hábitat esencial para otros organismos, incluidas las especies de
valor comercial (Husebo et al., 2002), éstos animales
también serían afectados. La destrucción de hábitat
esenciales para peces puede ser una de las causas adicionales por las cuales muchas pesquerías de aguas
profundas, que han sido colapsadas en los últimos 20
años, no se hayan recuperado (Koslow, 2007).
AMENAZAS
Mucho se ha escrito en años recientes en relación a las
amenazas que enfrenta la biodiversidad de los MS
(e.g., Rogers, 1994; Gubbay, 1999, 2003; Butler et al.,
2001; Koslow et al., 2001; Morato et al., 2006; Pitcher
et al., 2007; Koslow, 2007). Sin duda, al igual que las
principales cadenas de MS, la amenaza más inmediata
en términos de su escala geográfica e impacto es la
pesca comercial. Debido a que especies comerciales
habitan el área y han sido sujeto de algunas capturas
con buenos rendimientos (Arana, 2003) y se han estimado biomasas que aparentemente permitirían una
explotación comercial (Pakhorukov et al., 2000), es
probable que con otras especies del área ocurra lo
mismo en el futuro cercano. Actualmente, las actividades de pesca comercial están tecnológicamente
habilitadas para operar sin inconvenientes hasta
aproximadamente los 1500 m de profundidad, y por lo
tanto, pueden afectar negativamente elementos estructurales o especies claves de varios MS de Nazca y
Salas y Gómez. La sensibilidad del área es alta, especialmente a aquellas prácticas pesqueras que usan
artes de pesca que entran en contacto con las cimas o
laderas de los MS.
Por otro lado, debido a las altas probabilidades de
encontrar ricos yacimientos de mineral en el área (Fig.
2), la minería submarina emerge como otra amenaza
para la biodiversidad de los MS. Los efectos de estas
probables actividades son en extremo inciertos, dado
que dependerán de las tecnologías que se utilicen en la
extracción. Sin embargo, Koslow (2007) indica que
“un proyecto minero de 20 años de operación, para
uno o dos yacimientos, tendría impactos severos sobre
un área de al menos 10.000-20.000 km2, y probablemente varias veces mayor”. Dichos impactos estarían
relacionados con la remoción directa de fauna asociada al sedimento, y las perturbaciones producidas por la
suspensión y resedimentación. Dado que actualmente
se ve lejana la posibilidad de explotaciones mineras en
el área de Nazca y Salas y Gómez, se estima que el
escenario es óptimo para diseñar políticas, normas y
estrategias que concilien la eventual explotación minera y la conservación de los ecosistemas y la biodiversidad asociada a los MS de estas cordilleras, situación
que en el área de la alta mar ya ha comenzado a ser
abordada por la Autoridad Internacional de los Fondos
Marinos (AIFM).
MANEJO
Prácticas actuales de manejo
Jurisdiccionalmente debemos distinguir las prácticas
de manejo y conservación de recursos pesqueros y
ecosistemas marinos en el área de las cordilleras submarinas de Nazca y Salas y Gómez en dos: (i) aquellas
asociadas a la jurisdicción de Chile, y (ii) a la alta mar
(aguas internacionales). Para el primer caso se considera el área que circunscriben las ZEEs y Mares Territoriales (MTs) asociados a isla de Pascua, isla Salas y
Gómez e islas Desventuradas. En el segundo caso, se
trata del área complementaria a la anterior y que cubre
las cadenas de MS analizados.
El área comprendida bajo jurisdicción chilena no
está sometida a alguna medida de conservación general, y existe una flota nacional autorizada para efectuar
prácticas pesqueras con los artes y aparejos comúnmente empleados por la flota industrial y artesanal, así
como para el desarrollo de otras actividades productivas (e.g., extracción de hidrocarburos y minería submarina). La única restricción pesquera específica que
rige para el área está referida a la pesquería de alfonsino, en que las capturas efectuadas en el área son descontadas de la cuota global anual de captura, debido a
que la unidad de pesquería de esa especie ha sido fijada para el MT y ZEE, continental e insular, por fuera
del área de reserva artesanal (Decreto exento Nº644 de
2004, Ministerio de Economía, Fomento y Reconstrucción, Chile). Un caso aparte, lo constituyen tres
pequeñas áreas marinas inmediatamente adyacentes a
isla de Pascua, las que han sido declaradas Áreas Marinas Costeras Protegidas (AMCP) (Decreto supremo
Nº547 de 1999, Subsecretaría de Marina, Chile). En
dichas áreas protegidas esta autorizada la realización
de todas aquellas actividades de carácter científico,
ecológico, arqueológico, cultural, educativo, turístico
y deportivo, especialmente de tipo subacuático.
Chile dispone de instrumentos legales para la administración y conservación marina de esta zona de
493
océano abierto, aunque la aplicación de dichos instrumentos requiere de un nivel de integración y articulación mayor para conciliar la aparente dicotomía entre
explotación y preservación de especies marinas (Fernández & Castilla, 2005). Así por ejemplo, aparte de
la clásica batería de medidas de manejo que dispone la
Ley General de Pesca y Acuicultura, su artículo 3.d
contempla la figura de Parques Marinos, en que las
actividades quedan restringidas a aquellas que se autoricen para propósitos de observación, investigación o
estudio, excluyendo las actividades pesqueras comerciales. Esta ley también contempla las Reservas Marinas orientadas a proteger stocks reproductivos a la vez
que permite niveles de actividad pesquera, pero la
aplicación de este instrumento está reservada a la zona
costera. Pareciera que las ya mencionadas AMCP
tienen un mayor potencial para la articulación conjunta de metas de conservación y explotación. Un ejemplo de esto es el AMCP “Lafken-Mapu-Lahual”, la
que co-existe junto a seis Áreas de Manejo y Explotación de Recursos Bentónicos. Finalmente, atendiendo,
además de las características ecológicas del área, la
belleza escénica que podría importar alguno de los
macizos submarinos de Nazca y Salas y Gómez, cabe
también considerar la figura de Monumento Natural.
Según Fernández & Castilla (2005), este último instrumento de protección se aplica al sector marino y
tiene por fin preservar ecosistemas naturales permitiendo actividades de investigación y educacionales.
En relación a la oceanominería, Saintard (2001)
indica que el Estado de Chile ya cuenta con la estructura legal básica para que esta actividad también pueda
efectuarse en aguas jurisdiccionales; más aún, ya se
han suscrito contratos especiales de operación para
sustancias minerales metálicas ubicadas en el subsuelo
de los fondos marinos del Estrecho de Magallanes y
de la bahía de Nassau (55°23’S, 67°50’W). Sin embargo, no es claro si las evaluaciones y estudios requeridos tienden a cautelar efectivamente la diversidad
biológica y los ecosistemas marinos que pudieran ser
afectados por estas actividades.
En lo relativo a la sección de alta mar, recientemente se han establecido medidas de conservación en
el área del Pacífico sur, las que también se aplican a
los MS de Nazca y Salas y Gómez. Dichas medidas de
protección se han generado en el marco de las negociaciones para crear la ORAP PS. Estas medidas tienen un carácter interino (desde 30 septiembre 2007
hasta la entrada en vigencia del acuerdo que crea la
ORAP PS), son voluntarias y están principalmente
referidas a actividades de pesca pelágica (con excepción de calamares) y de fondo. En lo que respecta a la
pesca de fondo las medidas de administración interinas establecen lo siguiente:
494
− Pueden ser revisadas por las partes que negocian la ORAP PS. Prueba de ello es la propuesta
de Chile en la VI reunión de la ORAP PS en el
sentido de complementar las medidas interinas
sobre pesca pelágica, con el ‘congelamiento’ de
las capturas de jurel.
− Limitan la captura o el esfuerzo pesquero en las
pesquerías de fondo a los niveles promedio
anuales en el período comprendido entre el 1 de
enero de 2002 y el 31 de diciembre de 2006.
− No permiten la expansión de actividades de
pesca de fondo a nuevas regiones (áreas donde,
para el periodo anterior, no ha habido pesca de
fondo). Sin embargo, permite tales actividades
en dichas zonas en el marco de investigaciones
para la evaluación de stocks, previa remisión a
la secretaria interina de la ORAP PS del plan de
investigación.
− Cierran las áreas donde se conoce que existen (o
es probable que se localicen) EMV. Sin embargo, se podrá operar en dichas áreas cuando, basados en una evaluación científica, se hayan establecido medidas de administración de los
stocks pesqueros y se hayan tomado medidas
para prevenir impactos adversos significativos
sobre EMV.
− Requieren del uso de sistemas de posicionamiento satelital para las naves de pesca de fondo y el embarque de observadores científicos.
− Fijan el procedimiento para la confección, remisión y revisión (por parte del Grupo de Trabajo
Científico, GTC) de las evaluaciones científicas
de pesca de fondo. El estándar para guiar la
confección y revisión de dichas evaluaciones
científicas ha sido desarrollado por el GTC y está contenido en el borrador denominado “Benthic Assessment Framework”.
La efectividad de estas medidas y su cumplimiento
es algo que aun está por verse. Sin embargo, en relación a la efectividad de las mismas, se puede anticipar
que en su diseño ya se perciben algunos vacíos, tales
como (i) son de carácter voluntario, por lo que no
obligan ni establecen sanciones para las partes; (ii)
pueden ser revisadas (y por lo tanto flexibilizadas) a
pedido de cualquiera de las partes; (iii) no consideran
cursos de acción o medidas en caso que naves de países no parte de las negociaciones realicen actividades
de pesca de fondo en el área; (iv) se podría permitir el
desarrollo de actividades extractivas, bajo el expediente de evaluaciones directas de stocks, con impactos
negativos en EMV; y, (v) la Federación Rusa ha manifestado abiertamente su oposición a elementos sustan-
tivos de tales medidas, abriendo un espacio para la
inefectividad de las mismas.
Se ha indicado que las Áreas Marinas Protegidas
(AMPs) en alta mar son una herramienta importante y
legalmente factible, para la conservación y utilización
sustentable de la biodiversidad marina (Kimbal, 2005;
IUCN, 2006; Gjerde, 2007). En la Cumbre Mundial
sobre el Desarrollo Sustentable de Johannesburgo
2002 los gobiernos han fijado el objetivo de desarrollar al 2012 una red de AMPs, sobre la base de la información científica y consistente con el derecho internacional. En apoyo a la consecución de este objetivo, la Asamblea General de las Naciones Unidas (resolución A/RES/61/105), las partes de la Convención
sobre Diversidad Biológica (CBD), el Comité de Pesca de FAO y la conferencia de revisión del acuerdo de
Nueva York (Anon., 2006) han hecho llamados para
un mayor uso de las AMPs, de tal forma de apoyar un
manejo pesquero sustentable y asistir en la protección
de la biodiversidad marina. Es más, según Gjerde
(2007), a nivel regional, hay programas activos para el
desarrollo de AMPs en alta mar del Atlántico noreste,
el Mediterráneo y el océano Austral, éste último en el
marco de la Convención para la Conservación de los
Recursos Vivos Marinos Antárticos (CCRVMA). En
consecuencia, las AMPs se configuran como un potente elemento de administración y conservación que
puede ser aplicado al área de los montes submarinos
de Nazca y Salas y Gómez.
La CONVEMAR considera los recursos minerales
del suelo y subsuelo del área de alta mar como ‘patrimonio común de la humanidad’, y ha dispuesto que la
AIFM actúe en nombre de la humanidad para manejar
la explotación de esos recursos minerales. A pesar que
actividades mineras en alta mar de las cordilleras
submarinas de Nazca y Salas y Gómez parece algo
bastante lejana, aunque posible debido a que se han
constatado montes con un alto grado de cobalto en la
corteza (Fig. 2), la ISA ha promulgado un código de
prácticas mineras que regula el acceso y extracción de
nódulos polimetálicos del fondo marino y esta desarrollando regulaciones adicionales para minerales que
se encuentran en MS de alta mar (Stone et al., 2004)
En síntesis, en la alta mar del Pacífico suroriental
existen algunas medidas que regulan actividades pesqueras y de oceanominería, las que se han diseñado
para evitar impactos adversos sobre ecosistemas marinos vulnerables, aunque éstas no parecen del todo
efectivas particularmente ante los efectos adversos que
pueden generar las actividades de pesca de fondo. Sin
embargo, como lo notan Kimball (2005) y Gjerde
(2007), actualmente existen oportunidades legales y
enfoques científicos que avalan el establecimiento de
medidas más efectivas como AMPs en alta mar. De
todos modos, se debe reconocer que aún queda trabajo
por hacer para establecer, manejar y controlar de manera consistente e integrada las AMPs en alta mar; ya
que como lo indica el grupo de trabajo especial para el
estudio de biodiversidad marina en alta mar de Naciones Unidas, si bien CONVEMAR debe ser el instrumento rector, varias son las organizaciones con rol y
mandato en esta temática (e.g., FAO, la AIFM, la
Organización Marítima Internacional, la CBD y
ORAPs). Para el caso de la zona bajo jurisdicción
chilena no se dispone de medidas particularmente
dirigidas a la conservación y administración de estos
importantes cordones de MS. Habida consideración de
la gran biodiversidad hasta ahora estudiada, la falta de
tales medidas es notable.
Opciones de manejo
Dados los dos tipos de regímenes jurisdiccionales que
afectan el área de Nazca y Salas y Gómez y la inminente creación de la ORAP PS, los aspectos de política y manejo pesquero merecen un análisis aparte y
profundo, el que hasta la fecha no se ha efectuado o al
menos no es públicamente conocido. De todas maneras, y so riesgo de una sobresimplificación, es posible
identificar tres tipos de opciones para enfrentar las
amenazas a la biodiversidad:
1. Una moratoria para toda el área, tanto en su componente de alta mar como de la zona bajo jurisdicción chilena, sería una buena alternativa mientras se consideran y desarrollan otras opciones para la gobernanza de los recursos marinos de fondo
del área. Precedentes de largo alcance que se pueden invocar para tal acción son la moratoria de
Naciones Unidas a las redes de enmalle de deriva
y la moratoria a la caza de ballenas de la Comisión Ballenera Internacional. Adicionalmente, en
una perspectiva más regional es posible indicar
como ejemplo que varias ORAP han cerrado recientemente áreas a la pesca para proteger los ecosistemas marinos vulnerables que ahí se encuentran (Gjerde, 2007). Sin embargo, una medida de
este estilo claramente deja fuera otros valores que
deben ser igualmente considerados y ponderados,
como los sociales y económicos ligados a la actividad pesquera.
2. La entrada en vigor de la ORAP PS con autoridad
para regular las actividades de pesca de especies
discretas de la alta mar y conservar los ecosistemas asociados. La efectividad de las ORAP con
relación a las especies discretas ha sido fuertemente cuestionada en varios análisis internacionales y publicaciones. Quizás la única excepción
destacable es la CCRVMA, quien desde sus orígenes ha tenido en cuenta el principio precautorio
495
y el enfoque ecosistémico. Por lo tanto, aún está
por verse el mérito de las medidas interinas y
otras que puedan acordarse en el seno de la ORAP
PS. Adicionalmente, las acciones que ejerza la
ORAP PS en relación a Nazca y Salas y Gómez
no necesariamente salvaguardan dicho ecosistema
en el área de la ZEE de Chile, al tiempo que parece difícil que medidas de manejo fijadas para la
alta mar por la ORAP PS se extiendan a aguas de
jurisdicción chilena.
3. La declaración de un sistema representativo de
Áreas Marinas Protegidas (AMPs), tanto para alta
mar como para aguas bajo jurisdicción de Chile.
Con una iniciativa de este estilo, los asuntos jurisdiccionales no serían tocados, pero el nivel de
coordinación requerido sería exigente. La conservación a través de la designación de AMPs requerirá una mezcla de medidas nacionales y supranacionales que sean legalmente efectivas y controlables en la práctica. Las AMPs, dependiendo del
alcance que tengan, podrían permitir la inclusión y
consideración de múltiples valores y visiones, no
solo de los usuarios directos de los recursos
hidrobiológicos, sino que además de otros actores
como grupos de científicos, ONGs y público en
general. En la zona bajo jurisdicción chilena existe un sustrato legal para la implementación de tales AMPs, en tanto que en el área de alta mar es
posible indicar que hay ejemplos de programas
activos para el desarrollo de AMPs tanto en el
Atlántico noreste, como en el Mediterráneo y el
océano Austral. Más aun, la reciente conferencia
de revisión del Acuerdo de Nueva York, sobre especies transzonales y altamente migratorias, reconoce a las AMPs como una herramienta efectiva
de conservación en la alta mar y recomienda a los
países y ORAP que se desarrollen criterios para su
aplicación (Anon., 2006).
Un último desarrollo en materia de manejo y protección de EMV en la alta mar, y que esta en línea con
la opción de manejo anterior, es la reciente Guía Internacional Para el Manejo de las Pesquerías de Aguas
Profundas en la Alta Mar, adoptada por los miembros
de FAO después de dos años de preparación y negociación (FAO, 2008). En su párrafo 66 se exhorta a los
estados y ORAP a cerrar a la pesca de aguas profundas aquellas zonas de alta mar donde se hayan identificado o es probable que existan EMV. El cierre de
tales áreas, como lo deja entrever el mismo reporte,
debiera ser consistente y estar incorporado en planes
de administración de pesquerías de aguas profundas,
con lo cual – aunque no es explícitamente mencionado
en el reporte final – se articula la figura de AMP explicitada en versiones preliminares de dicho reporte.
496
CONCLUSIONES
La literatura científica disponible en relación a los MS
que conforman las cadenas de Nazca y Salas y Gómez
es fragmentada, escasa y en algunos casos de difícil
acceso, básicamente por el idioma en que ha sido escrita y porque algunos datos y reportes no son de carácter público. Sin embargo, algunos artículos (especialmente el de Parin et al., 1997) y bases de datos
biológicas y geológicas de libre disposición se destacan como un esfuerzo integrador de la información
generada por algunas expediciones, tal es el caso de
los sitios web “SeamountsOnline” (datos biológicos) y
“Earth Reference Data and Models” (datos geológicos). Los datos y análisis oceanográficos, que pueden
ser asociados a los montes de esta zona, han sido generados en el contexto de estudios que no consideran a
los MS como sujeto de análisis. Sin embargo, una
compilación y sistematización de dicha información
podría permitir un análisis preliminar del área o el
planteamiento de hipótesis científicas para el desarrollo de futuras investigaciones. Existe una carencia
total respecto de estudios que analicen los efectos de
la pesca, tanto en las especies que habitan dichos montes como en el ecosistema mismo. Por lo anterior, el
presente documento constituye el primer intento integrador de la información científica disponible, permite
identificar las áreas en que se carece de dicha información y por lo tanto la programación de futuras investigaciones, al tiempo que realza la importancia de
estas cordilleras submarinas como sujeto de conservación y administración por parte de la ORAP PS, y
particularmente del Gobierno de Chile. Sin embargo,
se reconoce que una visión verdaderamente holística
respecto de este ecosistema debe incorporar no sólo
estudios científicos, sino que también jurídicos, económicos y geopolíticos, con el objeto de sentar las
bases que permitan una adecuada gobernanza y sustentabilidad de las comunidades biológicas, del ecosistema y de los eventuales usos de los recursos naturales
en el área.
Los montes de Nazca y Salas y Gómez son uno de
los accidentes geográficos submarinos más relevantes
del Pacífico suroriental. La principal hipótesis que
explica su creación, indica que estos alineamientos
montañosos son de origen volcánico y estarían formados por el hotspot de Pascua. En conjunto tienen una
extensión de 2.900 km, y entre 100 y 300 km de ancho. El 65% de los 144 MS que componen Nazca y
Salas y Gómez se localizan en aguas internacionales
de la alta mar, mientras que el resto en aguas jurisdiccionales chilenas. La superficie marina proyectada por
ambos cordones representa menos del 5% de la alta
mar en las áreas FAO 87.2 y 87.3. Sin embargo, para
estas mismas áreas contiene casi de la mitad de los
MS. Hasta el momento, sólo la lejanía de dichos cordones submarinos ha permitido que no se valore en su
real magnitud la importancia científica y ecológica
que encierran.
Los cordones de Nazca y Salas y Gómez alojan un
conjunto de MS con una excepcional biodiversidad y
una de las tasas de endemismo más altas reportadas
para este tipo de ecosistemas (46,3% de 164 invertebrados y 41,2% de 171 peces identificados), las que
incluso superan las de otros tan extraños como los
campos de fuentes hidrotermales. No sólo especies
son endémicas de dichos montes, sino que también
nuevos géneros han sido descubiertos, los que también
son únicos en el área. A pesar de su relativa cercanía
con el continente americano, su fauna íctica de gran
profundidad está más asociada con la que es posible
encontrar a iguales profundidades en las cercanías de
Japón, Australia, Hawai o Nueva Zelanda, antes que a
lo largo de la costa sudamericana. Así, este impresionante alineamiento montañoso submarino, ha sido
denominado con propiedad un ‘hotspot’ biológico y
un reducto de la fauna del Pacífico indoccidental en el
Pacífico suroriental.
Especies altamente vulnerables han sido registradas para la zona de los MS de Nazca y Salas y Gómez,
tales como algunos tipos de corales pétreos, esponjas y
peces de baja resilencia. Estos ensambles biológicos y
la inusualmente alta productividad primaria en el área,
formarían la base del ecosistema epipelágico asociado,
donde otras importantes especies ocurren. Adicionalmente, los montes de Nazca y Salas y Gómez alojan
un conjunto de especies que han sido sujeto de actividades pesqueras en el área (Beryx splendens, Projasus
bahamondei y más asociado a la zona pelágica,
Xiphias gladius), o que conforman pesquerías comerciales en otras latitudes, tales como Trachurus symmetricus murpyi, Emmelichthys cyanescens, E. elongatus,
Decapterus muroadsi, Zenopsis oblongus, Epigonus
elegans, Helicolenus lengerichi, Pentaceros quinquespinis y Chaceon chilensis. Debido a esto, la pesca
comercial emerge como una de las amenazas más
inminentes para el área, particularmente en la zona
bajo jurisdicción chilena ya que hasta la fecha no se
han tomado medidas de manejo y conservación orientadas, y se ha empezado a verificar una baja pero incipiente actividad de la flota de arrastre chilena.
RECOMENDACIONES
Si bien hay muchas consideraciones económicas, político, jurídicas y prácticas que están más allá del ámbito de ésta revisión, se postula que, tomando en cuenta
los objetivos superiores de la investigación y conser-
vación, las siguientes recomendaciones son pertinentes para el caso de los ecosistemas asociados a las
cordilleras submarinas de Nazca y Salas y Gómez:
− Por los altos costos que implican las investigaciones científicas, y el carácter jurisdiccional
del área, se recomienda la búsqueda de una mayor coordinación y cooperación internacional
para afrontar los estudios que los estamentos
políticos requerirán para la toma de medidas de
administración. Como punto de partida, tres actividades resultan relativamente fáciles de implementar: la traducción de varios documentos
científicos redactados en ruso, la confección de
una base de datos integral (biológica, geológica,
oceanográfica y pesquera), y la incorporación
de esta zona a programas internacionales de investigación científica como el CenSeam.
− En atención a lo anterior, se recomienda la confección de estudios político-jurídicos, a fin de
evaluar las alternativas legales y políticas, tanto
en términos nacionales (i.e., Chile) como internacionales, para la creación de un sistema de
AMPs, con su respectivo plan de administración, en la zona de Nazca y Salas y Gómez.
Análisis económicos, como evaluaciones no basadas en el mercado, debieran ser parte de estos
estudios, así como aspectos prácticos de control
y fiscalización.
− Finalmente, se recomienda la implementación
de programas de información pública selectiva
y masiva. Selectiva, en términos de desarrollar
seminarios (o similares) de orden científico y
legal a particulares audiencias que tengan algún
interés directo con el área, con el objeto de
compartir/difundir información especializada.
Masiva, en términos de destacar la importancia
ecológica y vulnerabilidad de los ecosistemas
asociados a los MS de Nazca y Salas y Gómez.
Programas de esta naturaleza, sin duda que aumentarán la transparencia en el proceso de manejo y darán un impulso al desarrollo de nuevas
investigaciones.
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physical processes and their influence on the seamount ecosystem. OASIS report, University Hamburg, 40 pp. http://www1.uni-hamburg.de/oasis// pages/publications/ oceanography.pdf. Revised: 4 December 2007.
Wilson, R.R. & R.S. Kaufmann. 1987. Seamount biota
and biogeography. In: B. Keating, P. Fryer, R. Batiza
& G. Boehlert (eds.). Seamounts, Island and Atolls.
Geophys. Monogr., 43: 355-377.
Woods, M.T. & E.A. Okal. 1994. The structure of the
Nazca Ridge and Sala y Gómez seamount chain from
the dispersion of Rayleigh waves. Geophys. J. Int.,
117(1): 205-222.
Yáñez, E., C. Silva, J. Marabolí, F. Gómez, N. Silva, E.
Morales, A. Bertrand, J. Chong, R. Rojas, A. Órdenes, J. Campalans & A. Gamonal. 2004. Caracterización ecológica y pesquera de la cordillera de Nazca
como área de crianza del Pez espada. Informe Final,
Proyecto FIP N° 2002–04: 389 pp.
Yáñez, E., C. Silva, N. Silva, A. Órdenes, F. Leiva, P.
Rojas & J. Chong. 2006. Caracterización ecológica y
pesquera de la cordillera de Nazca como área de
crianza del Pez espada, fase II. Informe Final, Proyecto FIP N° 2004–34: 236 pp.
Yañez, E., C. Silva, R. Vega, L. Alvarez, N. Silva, S.
Palma, S. Salinas, E. Menschel & V. Haussermann.
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Final, Proyecto FIP Nº 2006-57: 246 pp.
Lat. Am. J. Aquat. Res., 37(3): 501-512, 2009
Deep-sea seamount fisheries: a global review
501
Review
Deep-sea seamount fisheries: a review of global status and future prospects
Malcolm R. Clark
NIWA, Private Bag 14-901, Wellington, New Zealand
ABSTRACT. Seamounts support a large number and wide diversity of fish species. A number of these species can form aggregations for spawning or feeding and are the target of large-scale trawl fisheries. Since the
1970s, seamounts throughout the worlds’ oceans have been explored for commercial resources, starting with
efforts by the Soviet Union and Japan, which deployed distant water fleets around the world. Since then, a
large number of countries have pursued fisheries on seamounts, especially in the deep sea. The total cumulative catch from seamount trawl fisheries exceeds two million tonnes. Catch histories for many deep-sea species show rapidly declining landings, and careful management is required to increase the chances of sustainable fisheries. The low productivity of many seamount species limits the prospects for the large-scale exploitation of fish and invertebrate resources on seamounts.
Keywords: deep-sea, fisheries, seamounts, fisheries management, sustainability, orange roughy, Hoplostethus
atlanticus.
Pesquerías de aguas profundas realizadas en montes submarinos: revisión global
de su estado y perspectivas futuras
RESUMEN. Los montes submarinos constituyen el hábitat de una vasta y amplia variedad de especies ícticas.
Parte de estas especies pueden formar agregaciones reproductivas o alimenticias, siendo objeto de importantes
pesquerías de arrastre. A partir de la década de los 70´ los montes submarinos en los diversos océanos fueron
explorados en busca de recursos comerciales, labores que se iniciaron con la expansión de flotas de aguas distantes de la Unión Soviética y Japón alrededor del mundo. Desde ese momento, un gran número de otros países ha desarrollado pesquerías en montes submarinos, especialmente en aguas profundas. La captura total
acumulada que se ha extraído en los montes submarinos excede a dos millones de toneladas. La historia de las
faenas pesqueras realizadas en numerosas especies de aguas profundas muestra una rápida disminución en los
desembarques, razón por la cual requieren de un cuidadoso manejo para incrementar la oportunidad de lograr
la condición de pesquerías sustentables. La baja productividad observada en diversas especies indica una limitada posibilidad de desarrollar pesquerías a gran escala, tanto de peces como de invertebrados, en los montes
submarinos.
Palabras clave: aguas profundas, montes submarinos, pesquerías, manejo pesquero, sustentabilidad, orange
roughy, Hoplostethus atlanticus.
________________________
Corresponding author: Malcolm R. Clark ([email protected])
INTRODUCTION
Seamounts are prominent features of the seafloor
throughout the oceans of the world. Their numbers are
unknown, but recent studies based largely on satellite
altimetry have estimated that there could be tens of
thousands of large seamounts (Wessel, 2001; Kitch-
ingman & Lai, 2004; Hillier & Watts, 2007). Their
distribution is widespread throughout the world’s
oceans, especially in the Pacific (Fig. 1).
Seamounts support a large number and wide diversity of fish species. A total of almost 800 species have
been recorded from seamounts (Froese & Sampang,
2004; Morato et al., 2006; Morato & Clark, 2007).
502
Figure 1. Estimated global distribution of large seamounts (elevation > 1500 m). Based on data from Kitchingman & Lai
(2004).
Figura 1. Distribución mundial estimada de grandes montes submarinos (elevación > 1500 m). Según datos de Kitchingman & Lai (2004).
Most of these also occur widely on the continental
shelf and slope habitat, but seamounts can be an important habitat for commercially valuable species that
may form dense aggregations for spawning or feeding
(Clark, 2001) and on which a number of large-scale
fisheries have developed in the deep-sea.
Many of these fisheries, however, have not been
sustainably fished or managed. A number have shown
a ‘boom and bust’ pattern, with catches rapidly developing and declining within a decade (e.g. Uchida &
Tagami, 1984; Clark, 2001; Vinnichenko, 2002a).
These patterns have raised concerns over whether such
fisheries can be sustainable (e.g. Roberts, 2002;
Gianni, 2004; Stone et al., 2004).
This paper briefly describes deep-sea seamount
fish and trawl fisheries, reviews aspects of their sustainability, discusses what is required for effective
management of both fisheries and the seamount habitat, and considers prospects for large-scale commercial
exploitation of fish resources on seamounts. The study
is restricted to demersal finfish, although seamount
fisheries also occur for surface and midwater fish,
crustaceans, and squids (see Rogers, 1994 and papers
in Pitcher et al., 2007).
Description of seamount fishes
The definition of “deep sea” varies between organizations and countries. The FAO criterion is beyond the
continental shelf/slope break, typically occurring at
about 200 m. However, this depth-limit means a large
number of shallow-water species are included where
their depth distribution extends beyond 200 m. Hence,
in this paper, the focus is on a more ecological definition that recognizes fish with low productivity relative
to inshore continental shelf species, which are typically deeper than 400-500 m (FAO, 2008) (Table 1). It
is not possible to generalize about biological characteristics, as deepwater seamount species span a wide
range of productivity values (e.g. rubyfish are relatively short-lived and fast growing compared with
orange roughy), but it is widely recognized that these
deep-sea species are less productive and more vulnerable to fishing pressure than shelf species (e.g.
Gordon, 2005; Japp & Wilkinson, 2007; Sissenwine &
Mace, 2007).
Deep-sea trawl fisheries occur on seamounts for a
number of species. These include alfonsino (Beryx
splendens), black cardinalfish (Epigonus telescopus),
orange roughy (Hoplostethus atlanticus), southern
boarfish (Pseudopentaceros richardsoni), macrourid
rattails (primarily roundnose grenadier Coryphaenoides rupestris), oreos (several species of the
family Oreosomatidae, including the smooth oreo
Pseudocyttus maculatus and the black oreo Allocyttus
niger), and toothfish (Patagonian toothfish Dissostichus eleginoides and Antarctic toothfish D. mawsoni)
(Clark et al., 2007). Other fisheries occur over
503
Table 1. Bathymetric distribution and biological characteristics of commercial fish species on seamounts. Depth is the
main commercial range. Data on maximum age, resilience (population doubling time), and intrinsic extinction vulnerability, the latter based on Cheung et al. (2005) and consisting of a relative measure ranging from 1 (very low) to 100 (very
high), are from Fishbase.
Tabla 1. Distribución batimétrica y características biológicas de los peces comerciales capturados en montes submarinos.
La profundidad se refiere a rangos en que se efectúan las pescas comerciales: edad máxima, productividad relativa (lapso
en que se duplica la población) y vulnerabilidad intrínseca de extinción. De acuerdo a Cheung et al. (2005), una medida
relativa varía de 1 (muy bajo) a 100 (muy alto), datos tomados de Fishbase.
Species
Scientific name
Main depth
range (m)
Maximum
age
(years)
Resilience
(years)
Intrinsic
extinction
vulnerability
Alfonsino
Beryx splendens
300-600
25
5-14
65
Cardinalfish
Epigonus telescopus
500-800
100
14
70
Rubyfish
Plagiogeneion rubiginosum
250-450
10
2-4
49
Blue ling
Molva dypterygia
250-500
20
5-14
73
Black scabbardfish
Aphanopus carbo
600-800
30
5-14
63
Sablefish
Anoplopoma fimbria
500-1,000
115
>14
76
Pink maomao
Caprodon spp.
300-450
2-4
50
Southern boarfish
Pseudopentaceros richardsoni
600-900
2-4
42
Pelagic armourhead
Pseudopentaceros wheeleri
250-600
11
7
57
Orange roughy
Hoplostethus atlanticus
600-1,200
150
>14
74
Oreos
Pseudocyttus maculatus,
Allocyttus niger
600-1,200
100
>14
72
Bluenose
Hyperoglyphe antarctica
300-700
15
5-14
74
Redfish
400-800
75
>14
75
Roundnose grenadier
Sebastes spp. (S. marinus,
S. mentella, S. proriger)
Coryphaenoides rupestris
800-1,000
54
5-14
78
Toothfish
Dissostichus spp.
500-1,500
20–30
5-14
86
Notothenid cods
Notothenia spp.
200-600
15-20
5-14
58
seamounts, such as those for pelagic species (mainly
tunas), near-bottom fishing for mackerels, and target
species for smaller scale line fisheries (e.g. black
scabbardfish Aphanopus carbo) (FAO, 2004; da Silva
& Pinho, 2007).
Many of the main commercial seamount species
are widespread, especially through the Atlantic, Indian, and South Pacific oceans (Table 2). A number of
Southern Hemisphere species are found in the North
Atlantic, but do not extend into the North Pacific (e.g.
orange roughy, oreos). Some species are more localised to the North Atlantic (e.g. roundnose grenadier,
blue ling, Sebastes mentella, S. marinus), and sablefish occur only in the North Pacific.
Seamount fisheries
Global overview
Seamount fisheries have taken place, or currently
occur, on a large number of seamounts throughout the
worlds’ oceans. These are prominent in the Pacific
ocean, but also in the southern Indian ocean, the MidAtlantic Ridge in the north Atlantic, and off the African coast in the south Atlantic (Fig. 2).
The largest seamount trawl fisheries have occurred
in the Pacific ocean (Koslow, 2007; Clark et al.,
2007). In the 1960s to 1980s, large-scale fisheries for
pelagic armourhead and alfonsino took place on the
Hawaiian and Emperor seamount chains in the north
504
Table 2. Geographical distribution of commercial fish species (+ indicates occurrence in that ocean).
Tabla 2. Distribución geográfica de las especies comerciales (+ indica presencia en un océano particular).
North
Atlantic
South
Atlantic
North
Pacific
South
Pacific
Indian
Ocean
Alfonsino
+
+
+
+
+
Cardinalfish
+
+
+
+
+
+
+
Species
Rubyfish
Blue ling
+
Black scabbardfish
+
Sablefish
+
Pink maomao
+
Southern boarfish
+
Pelagic armourhead
Orange roughy
Southern
Ocean
+
+
+
+
+
+
+
Oreos
+
+
+
+
Bluenose
+
+
+
Redfish
+
Roundnose grenadier
+
+
+
Toothfish
+
+
+
+
Notothenid cods
+
+
+
+
Figure 2. The distribution of major seamount/ridge fishing grounds (from Clark et al., 2007).
Figura 2. Principales montañas y cordilleras submarinas donde se realizan faenas de pesca comercial (tomado de Clark et
al., 2007).
505
Pacific. In total, about 800,000 ton of pelagic armourhead and about 80,000 ton of alfonsino were taken. In
the southwest Pacific, fisheries for orange roughy,
oreos, and alfonsino were large and continue to be
locally important. Orange roughy has also been the
target of fisheries on seamounts off the central coast of
Chile in the southeastern Pacific, on the Mid-Atlantic
Ridge in the north Atlantic, off the west coast of
southern Africa, and in the southwest Indian ocean.
Roundnose grenadier was an important fishery for the
Soviet Union in the North Atlantic, where catches
were over 200,000 tonnes. Smaller fisheries for alfonsino, mackerel, and cardinalfish have occurred on
various seamounts in the mid-Atlantic, southeast Pacific, and off the coast of north Africa. In the southern
ocean, fisheries for toothfish, notothenids, and icefish
can occur on seamounts as well as on slope and bank
areas. Most of these seamounts are fished with bottom
trawls, but several are also subjected to midwater
trawl and longline fisheries.
In total, the international catch of the main commercial demersal fish species on seamounts by distantwater fishing fleets is estimated to be over 2.15 million tonnes of fish since 1968 (Table 3) (Clark et al.,
2007). Hence, seamount fisheries have contributed
only a very small proportion of the total global wildfish catch, which averaged about 60 million tonnes per
year over the same period (Csirke, 2005).
South American fisheries
Most large volume deepwater fisheries have occurred
in other regions, but several fisheries have developed
off South America on seamounts. Off Brazil, a major
programme of exploratory trawling between 2000 and
2006 covered a large part of the coast, although seamounts were of secondary importance in this work,
which focused on the upper slope for finfish and
shrimps (Perez et al., 2009b). Seamounts of the Fernando de Noronha and Vitoria-Trinidade chains have
been exploited, although mainly with longlines (Hazin
et al., 1998, Martins et al., 2005) and only limited
trawling for groupers (Epinephelus spp.) (Perez et al.
2009a). During the 1980s, trawlers from the then Soviet Union fished on the Vitoria-Trinidade and Martin
Vaz seamount chains and developed a fishery for alfonsino on the Rio Grande Rise (Clark et al., 2007).
Table 3. Historic catches of the main fish species from seamounts, major fishing periods, and main gear types used in
seamount fisheries (derived from data in Clark et al., 2007).
Tabla 3. Capturas históricas de las especies más relevantes capturadas en montes submarinos, periodo de pesca más importante y principal tipo de arte de pesca empleado en la pesquería (datos tomados de Clark et al., 2007).
Common name
Alfonsino
Orange roughy
Oreos
Cardinalfish
Redfish
Southern boarfish
Pelagic armourhead
Mackerel species
Roundnose grenadier
Blue ling
Scabbard fish
Sablefish
Bluenose
Rubyfish
Pink maomao
Notothenid cods
Toothfish
Total
Total historical
catch (ton)
166,950
419,100
145,150
52,100
54,450
9,600
800,000
148,200
217,000
10,000
75,000
1,400
2,500
1,500
2,000
36,250
12,250
2,153,470
Main fishery
years
1978-present
1978-present
1970-present
1978-present
1996-present
1982-present
1968-1982
1970-1995
1974-present
1979-80
1973-2002
1995-present
1990-present
1995-present
1972-1976
1974-1991
1990-present
Gear type
Bottom and midwater trawl, some longline
Bottom trawl
Bottom trawl
Bottom (and midwater trawl)
Bottom and midwater trawl
Bottom trawl
(Bottom) and midwater trawl
Bottom, and midwater trawl
Bottom trawl
(Bottom trawl), longline
Bottom trawl
Bottom trawl, longline
506
New Zealand fishery is really the only one that has
persisted over time and much of this is due to fishing
grounds in a restricted area of the Chatham Rise, to
the east of the main New Zealand islands. Seamounts
account for between 40 and 60% of the catch in New
Zealand (Clark & O’Driscoll, 2003), even though
serial depletion has occurred in some areas (Clark,
1999; Clark et al., 2000). The Australian fishery was
very large for a number of years between 1989 and
1993, when high catch rates of spawning fish on St
Helens seamount were regularly made, but the stocks
were rapidly depleted and quotas were progressively
reduced (Lack et al., 2003; Bax et al., 2005; Koslow,
2007). The St Helens fishery is now closed completely. A similar situation occurred in Namibia and
Chile where, despite extensive research and precautionary management objectives, catches have not been
sustained, and fisheries are now very small or just
bycatch. The southwest Indian ocean is another area
where large catches were taken for a short time, made
worse by a total lack of any management on the High
Seas, which saw an uncontrolled increase in effort in
the early 2000s (from five vessels in 1999 to over 35
in 2000) and a sharp drop in catches and catch rates
(FAO, 2002; Japp & James, 2005). Sissenwine &
Mace (2007) described these catch histories as following two patterns: in the first, small stocks were fished
down rapidly in only a few years before effective
management could be implemented and, in the second,
larger stocks were initially overestimated by research,
and this was often coupled by non-conservative management practises and “fishing-down” phases, which
lead to excessive depletion.
In the southeastern Pacific, Soviet trawling occurred on the Nazca and Salas y Gomez Ridges for
mackerel (Trachurus murphyi) and redbaits (Emmelichthys spp.), mainly in the 1970s but sporadic
exploratory fishing also occurred in the 1980s (Clark
et al., 2007; Gálvez, 2009). Off Chile, a commercial
fishery for orange roughy and alfonsino developed on
seamounts around the Juan Fernandez Archipelago in
1998 (Labbé & Arana, 2001, Guerrero & Arana,
2009). Orange roughy catches peaked at 1,870 ton in
2001, but declined thereafter (Paya et al., 2005). This
fishery was closed except for a research quota in 2006
following decreasing catches and stock size estimates
(Niklitschek et al., 2005, Sissenwine & Mace, 2007).
SUSTAINABILITY OF DEEPWATER
SEAMOUNT FISHERIES
Deep-sea seamount fisheries, even within areas of
national jurisdiction, have typically not maintained
high catch levels over time. There are many examples
of 'boom and bust' fisheries that developed and declined rapidly, sometimes within a few years or a decade (e.g. Uchida & Tagami, 1984; Koslow et al.,
2000; Clark, 2001). Orange roughy is commonly cited
as an example of this, as few of its fisheries in the
world have proven to be sustainable (e.g. Branch,
2001; Clark, 2001; Lack et al., 2003; Sissenwine &
Mace, 2007).
New Zealand fisheries have dominated global
catches (Fig. 3), although note that this figure includes
continental slope habitats as well as seamounts. The
120000
Ireland
SWIO
Chile
N. Atlantic
Namibia
Australia
TasmanSea
NewZealand
Catch (ton)
100000
80000
60000
40000
20000
0
78
80
82
84
86
88
90
92
94
96
98
00
02
04
06
Year
Figure 3. Estimated orange roughy catches for the main fishing areas around the world (compiled from various data
sources).
Figura 3. Capturas estimadas de orange roughy extraídas en las principales áreas de pesca del mundo donde se distribuye
esta especie (datos provenientes de diversas fuentes).
Orange roughy is one of the least productive commercial species, but is not necessarily an extreme example. Fisheries for other deep-sea species have also
shown low resilience to large catches, such as the
pelagic armourhead fishery off Hawaii in the 1970s,
alfonsino in the north Atlantic, roundnose grenadier
on the Mid-Atlantic Ridge, and deepwater notothenids
in the southern ocean (Clark et al., 2007). These fisheries have sometimes maintained catches by moving
to new grounds or by switching to other species as the
target species biomass has declined (e.g. increase in
alfonsino catches as pelagic armourhead was overfished on the Hawaiian seamounts (Clark et al.,
2007)). However, even relatively shallow species (e.g.
pink maomao, Caprodon longimanus) can be rapidly
depleted over seamounts, evidenced by a short-lived
fishery on the Lord Howe Rise, where Japanese catch
rates in 1976 decreased from 1.7 to 0.2 ton h-1 over
one year with a catch of not much more than 1000 ton
(Sasaki, 1986). Sissenwine & Mace (2007) listed 44
deep-sea (> 200 m) area species combinations, 27 of
which included stocks classed as overexploited or
depleted. No stocks were identified as recovering.
Once overexploited, few deep-sea fisheries have
shown signs of recovery. There are situations in which
fishing success for orange roughy has improved with a
reduction in effort levels, and fishers have reported
increased catches of alfonsino and pelagic armourhead
in some areas when the seamounts or fishing grounds
have not been fished for a period. However, this may
in part be related to fewer disturbances of aggregations with reduced trawling than an increase in stock
size (Clark & Tracey, 1991). Orange roughy stocks in
many areas generally continued to decline even when
the catch has been reduced to levels thought by scientists to be sustainable. Some analyses have suggested
depletion has not been excessive (Hilborn et al., 2006)
but uncertainty about stock assessments and, in particular, assumptions about recruitment are critical in
such evaluations. Irregular recruitment levels may be a
key factor for the recovery of deep-sea species (Clark,
2001; Dunn, 2007).
The example of orange roughy fisheries, in particular, has given strong insights into three generic aspects
that contribute to the lack of sustainability of deep-sea
seamount fisheries:
Biological characteristics
Deep species often exhibit high longevity (up to 100
years for several species, e.g. redfish, orange roughy),
late maturation (sometimes > 20 years before becoming mature, e.g. orange roughy, oreos), slow growth,
low fecundity (e.g. deepwater sharks, orange roughy),
intermittent recruitment (occurs with most species, but
507
with long-lived species there could be decades between good year classes), and spawning may not occur
every year (Morato et al., 2006; Morato & Clark,
2007). Intermittent spawning behaviour and the migration of aggregations to spawning grounds (“intermittent aggregation”) have also been proposed to explain
why some decreases in stock size appear to have been
greater than expected based solely on the fisheries
catch or why the levels of depletion have varied between different fishing grounds (e.g. Butterworth &
Brandao, 2005). These types of fish generally have
low rates of natural mortality and low production
rates, meaning recovery is slow. Table 1 indicates that
several of the major deepwater commercial fish species have a population doubling time (“resilience”) of
14 years or greater (e.g. cardinalfish, orange roughy,
redfish) and high vulnerability indices of 70 to 80.
Their biology is not evolved to cope with high levels
of natural predation and so they are more vulnerable to
overfishing than shallow water shelf species.
Habitat/fishery type
Many species aggregate on seamounts or ridge peaks
because of depth or oceanographic conditions (e.g.
Koslow, 1997). Such aggregations will be more vulnerable to overfishing and rapid depletion than those
in which species are more dispersed on shelf or slope
habitats. When aggregations are formed for spawning,
the effects may be greater because of the possible
disruption of spawning processes and reduced reproductive success (although this has rarely been documented). Target trawling on seamounts is often localized, and the density of tows per seamount area can be
high (e.g. O’Driscoll & Clark, 2005). Heavy bottom
trawl gear is used to tow on the rough, hard bottom,
which is often characteristic of seamounts, and the
invertebrate fauna, often dominated by large, slowgrowing, sessile organisms, are especially vulnerable
to damage by fishing gear (e.g. Clark & Koslow,
2007). Fishing grounds often occur offshore and so are
carried out by large powerful vessels with the ability
to work large gear, catch and process large amounts of
fish, and stay at sea for long periods.
Economic considerations can also be important.
The market value of some of the deepwater species is
high, which creates an incentive for commercial operators to target the species (Japp & Wilkinson, 2007).
Good catches will offset the relatively high operating
costs of vessels offshore and create pressure to continue fishing as stocks decline or if there are high costs
associated with industry funding of research and management (e.g. Francis & Clark, 2005).
508
Research and management limitations Francis & Clark
(2005) described issues affecting the sustainability of
orange roughy based on the New Zealand experience.
As well as a lack of knowledge of the biological characteristics and processes (mentioned above), they
emphasised how standard stock assessment techniques
were often difficult to apply in the deep-sea environment and given the aggregating nature of the species.
Punt (2005) and Sissenwine & Mace (2007) also discussed difficulties for estimating the stock size of
orange roughy and how uncertain such stock assessments are likely to be. This uncertainty in the science
has, at times, led to subsequent management responses
being too slow or insufficient (Bax et al., 2005; Francis & Clark, 2005). Precautionary management is
required and the standard target reference levels and
management concepts (e.g. MSY, fishing down practices) applied in several deep-sea fishing countries
(e.g. New Zealand) have proven risky and insufficiently conservative (Sissenwine & Mace, 2007).
Management of seamount fisheries
The “ecosystem approach” to fisheries management is
now widely advocated and applied in deep-sea fisheries (FAO, 2003). However, the inherent restrictions on
obtaining sufficient stock assessment or benthic habitat data (compared with nearshore shelf/slope fisheries) mean that management regimes typically operate
at a low level of knowledge, and management action
must occur in a highly precautionary manner. There is
an increasing body of literature on data, reporting
requirements, and appropriate management actions to
help ensure the sustainability of deep-sea fisheries
(Francis & Clark, 2003; FAO, 2007, 2008; Sissenwine
& Mace, 2007; Probert et al., 2007; Morato & Pitcher,
2008; Rogers et al., 2008).
Various management actions now include closed
seamounts, fishing method or gear restrictions, depth
limits, individual seamount catch quotas, bycatch
quotas, and habitat exclusion areas (e.g. hydrothermal
vents) (Probert et al., 2007). Closed areas are a common method to protect the habitat, but can be problematic because they can exclude fishing from productive grounds. Recent initiatives by some fishing consortia (e.g. southwest Indian Ocean Fisher’s Association, New Zealand Deepwater Group) have instigated
“Benthic Protected Areas (BPAs)” which the fishers
voluntarily avoid to prevent seafloor damage by bottom trawling. Industrial “buy-in” to environmental
protection is a positive step as long as science is involved to help design the BPA distribution and size so
they are representative and effective. Typically, the
fine spatial scale needed to research and manage sea-
mount stocks is problematic. Serial depletion of fish
stocks can occur quickly (Clark, 1999), yet catch rates
can be maintained even though biomass is being reduced (Clark, 2001; Lack et al., 2003; Francis &
Clark, 2005; Sissenwine & Mace, 2007). There is no
easy answer to setting appropriate precautionary catch
limits for new seamount fisheries, although restricting
effort to only a few vessels (e.g. Namibian orange
roughy fisheries; Boyer et al., 2001) and imposing
limits on the catch from a single seamount or feature
(e.g. New Zealand; Rogers et al., 2008) can help reduce the risk of rapid over-exploitation. An analysis of
seamount catch over time indicates that the initial
orange roughy biomass on a single seamount feature
may generally be only a few thousand tonnes (Clark et
al., 2001).
Effects of bottom trawling on the wider benthic
community and habitat also need to be considered
(e.g. Dayton et al., 1995; Hall, 1999; Clark & Koslow,
2007). The deep-sea fish community includes species
that have low productivity and can be vulnerable to
the effects of fishing, even if the fishery targets a different species. Seamounts can host endemic species or
species with a very restricted geographical distribution
(Rogers, 1994; Richer de Forges et al., 2000), as well
as habitat-forming fauna such as deep-sea corals and
sponges that are regarded as indicators of “vulnerable
marine ecosystems” (FAO, 2008). This has been part
of the justification for calls from NGOs in recent years
for a moratorium on bottom trawling on the High
Seas. Management, therefore, needs to balance exploitation and conservation, both of fisheries and seamount habitats (Probert et al., 2007). A mixture of
protected and open seamounts is one strategy that
appears to be successful off New Zealand (Brodie &
Clark, 2003).
Future prospects
Seamount fisheries for deep-sea species in the future
are likely to be small volume, high value fisheries.
The track record of the deeper species such as orange
roughy and oreos indicates that large catches will only
last a few years, and highly precautionary catch limits
may be needed if they are to be sustainable. More
productive seamount species such as alfonsino, scabbardfish, grenadier, and armourheads are more resilient to heavy fishing and have been classified as less
vulnerable (Gordon, 2005), but stocks appear to be
variable and are still unlikely to withstand high catch
levels for more than a few years. Where estimates
have been made, the biomass of many fish stocks on
seamounts is relatively low and does not exceed several hundreds of thousands of tonnes for even the most
abundant species (e.g. Sasaki, 1986; Vinnichenko,
1998, 2002b). An analysis of New Zealand seamount
fisheries for orange roughy suggests that few seamounts can support long-term catches of more than a
few hundred tonnes per year (Clark et al., 2001).
Japp & Wilkinson (2007) and Sissenwine & Mace
(2007) have both summarized “deep-sea” catches as
reported in FAO statistics up to 2005. The catch trends
for the main seamount species or family groupings
typically show a decline after an initial rapid increase
as the fisheries developed. Although FAO statistics
cover very large regions of the world and do not distinguish seamounts from slope fisheries, these patterns
are consistent with those estimated from specific seamount data by Clark et al. (2007).
Clark et al. (2007) summarized the global status of
the large offshore seamount fisheries. Their conclusions
were that intense fishery pressure on the seamounts of
the Corner Rise, north Azores area of the Mid-Atlantic
Ridge, and the Vavilov, Walvis, southwest Indian,
Emperor and Hawaiian ridges has resulted in the depression of many fish stocks, with no increase of catch
in these areas likely within the next few years. Relatively new fishing grounds such as seamounts on the
Norfolk, Lord Howe, Louisville, and south Tasman
Rise have been targeted for deepwater species such as
orange roughy and are also fully exploited. Some
areas of the northern Mid-Atlantic Ridge and some
offshore seamounts located in Antarctic waters and the
central oceanic regions may have some potential for
further exploitation. However, the volume of deep-sea
species is likely to be small and short-lived if fisheries
are not managed carefully. Such management will also
need, in the future, to take account of balancing fisheries
management with conservation of the benthic environment.
ACKNOWLEDGEMENTS
This paper is based on a presentation at the Deep Sea
fisheries special session at the XII COLACMAR in
Brazil, April 2007. My thanks to the Convenor of that
session (Dr. Angel Perez) and the conference organizers for funding to attend the conference. The contents
of the paper draw on a wide range of research over the
last decade, but particularly a NIWA project on Seamounts: their importance to fisheries and marine ecosystems (FRST contract no. CO1X0508). Two
anonymous journal referees made numerous useful
comments to improve the manuscript.
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Deep-water fisheries in Brazil
513
Review
Deep-water fisheries in Brazil: history, status and perspectives
José Angel Alvarez Perez1, Paulo Ricardo Pezzuto1, Robeto Wahrlich1 & Ana Luisa de Souza Soares1
1
Rua Uruguai 458, Centro, Itajaí , SC, Brazil
ABSTRACT. The recent development of deep-water fisheries off Brazil is reviewed from biological, economic, and political perspectives. This process has been centered in the southeastern and southern sectors of
the Brazilian coast (19°-34°S) and was motivated by the overfishing of the main coastal resources and a government-induced vessel-chartering program. Shelf break (100-250 m) operations by national hook-and-line
and trawl vessels intensified in the 1990s. Around 2000-2001, however, foreign-chartered longliners, gillnetters, potters, and trawlers started to operate in Brazilian waters, leading the occupation of the upper slope (250500 m), mostly targeting monkfish (Lophyus gastrophysus), the Argentine hake (Merluccius hubbsi), the Brazilian codling (Urophycis mystacea), the wreckfish (Polyprion americanus), the Argentine short-fin squid
(Illex argentinus), the red crab (Chaceon notialis), and the royal crab (Chaceon ramosae). Between 2004 and
2007, chartered trawlers established a valuable fishery on deep-water shrimps (family Aristeidae), heavily exploiting the lower slope (500-1000 m). Total catches of deep-water resources varied annually from 5,756 ton
in 2000 to a maximum of 19,923 ton in 2002, decreasing to nearly 11,000 ton in 2006. Despite intensive data
collection, the availability of timely stock assessments, and a formal participatory process for the discussion of
management plans, deep-water stocks are already considered to be overexploited due to limitations of governance.
Keywords: deep-water fishery, stock assessment, fishery management, southwest Atlantic, Brazil.
Pesquerías de aguas profundas en Brasil: historia, situación actual y perspectivas
RESUMEN. El reciente desarrollo de la pesca profunda en Brasil fue revisado desde perspectivas biológicas,
económicas y políticas. Este proceso se ha centrado en los sectores sureste y sur de la costa de Brasil (19°34°S) y fue motivado por la sobrepesca de los principales recursos costeros en conjunto con una política gubernamental de arriendo de buques pesqueros. Las operaciones de pesca sobre el borde de la plataforma (100250 m) por buques palangreros y arrastreros se intensificaron en la década del 90. Sin embargo, entre 2000 y
2001 empezaron a operar buques arrendados para la pesca con palangre, red de enmalle, nasas y arrastre en
aguas brasileras y lideraron el proceso de ocupación del talud superior (250-500 m) dirigido principalmente a
la captura del rape (Lophyus gastrophysus), merluza argentina (Merluccius hubbsi), brótola de profundidad
(Urophycis mystacea), chernia (Polyprion americanus), calamar argentino (Illex argentinus), cangrejo rojo
(Chaceon notialis) y cangrejo real (Chaceon ramosae). Entre 2004 y 2007, buques arrendados establecieron
una valorada pesquería de langostinos de profundidad (Familia Aristeidae) y explotaron intensamente los fondos del talud inferior (500-1000 m). Las capturas totales de recursos de aguas profundas variaron anualmente
de 5.756 ton en 2000 a un máximo de 19.923 ton in 2002, decayendo a cerca de 11.000 ton en 2006. No obstante, que fueron recolectados datos pesqueros en forma intensas, estuviesen disponibles oportunamente evaluaciones de stock y se haya llevado a cabo un proceso formal de discusión participativa de planes de manejo
para estas pesquerías, los stocks de aguas profundas han sido considerado en situación de sobrepesca debido a
limitaciones de gobernabilidad.
Palabras clave: pesca profunda, evaluación de stock, manejo pesquero, Atlántico sudoccidental, Brasil.
________________________
Corresponding author: José Angel Alvarez Perez ([email protected])
514
INTRODUCTION
The first records of demersal fishing beyond the
continental shelf waters of the Atlantic date back to
the 1960s when Soviet trawlers began to operate on
the northern mid-Atlantic ridge (Troyanovsky &
Lisovsky, 1995). This deep-water fishery, however,
throve from the 1980s onwards as the abundance of
shelf resources declined greatly and important technological and market limitations were overcome
(Piñeiro et al., 2001; Gordon et al., 2003). Headed
by French trawlers, a multispecies, deep-water fishery was established at depths of 800 to 1600 m during the 1990s, mostly in the northeast Atlantic
(Charuau et al., 1995; Iglesias & Paz, 1995; Gordon, 2001; Piñeiro et al., 2001; Lorance & Dupuoy,
2001). Nearly ten years later, fishing activity on
slope grounds began to emerge as a pattern off the
Brazilian coast in the tropical and subtropical
southwest Atlantic (Perez et al., 2003).
The Brazilian Economic Exclusive Zone (EEZ)
encompasses an area of 3.5 million km2, mostly
bathed by southwest Atlantic waters; roughly 25%
(911,000 km2) of this area is occupied by the continental shelf. Since its early development in the
1960s, a large-scale demersal fishery has been restrained to the inner shelf and is sustained by a few
coastal resources, most notably shrimps (i.e. Farfantepenaeus spp.), spiny lobsters (Panulirus spp.),
and groundfish of the families Sciaenidae (i.e. Micropogonias furnieri, Cynoscion spp., Macrodon
ancylodon, Umbrina canosai), Pimelodidae (i.e.
Brachyplatystoma vaillantii), Lutjanidae (i.e. Lutjanus spp.), and others (see Paiva et al., 1996 and
Haimovici et al., 2006a for reviews). For nearly 40
years, deep-water fishing was essentially scientific
or restricted to hand-line operations over slope
grounds and seamounts targeting rockfish (Paiva et
al., 1996; Peres & Haimovici, 1998). In addition,
Soviet trawlers explored the Martin Vaz (20-21°S,
36-39°W) and Rio Grande Rise (28°-35°S, 20°38°W) seamounts in the 1980s (Clark et al., 2007).
Despite a few government efforts to map the ocean
floor and assess potential resources, commercial
fishing was generally considered unproductive and
uneconomical beyond the shelf break (Haimovici et
al., 1994; Haimovici, 2007).
At the end of the 1990s, a new scientific program
set out to assess fishing potential in the Brazilian EEZ
(REVIZEE Program; Anon, 2006a). By then, however, fishing was already expanding to the outer continental shelf and slope due to economic losses experi-
enced by the industrial fleet, both overcapitalized and
facing major reductions in the abundance of their main
targets (Perez et al., 2001). Concurrent to this natural
process and to the REVIZEE scientific exploration, in
1998, the Brazilian fishing authorities decided to catalyze the commercial occupation of the EEZ through a
foreign vessel-chartering program. This program allowed national companies to operate in Brazilian waters with foreign vessels specialized in oceanic and
deep-water fisheries provided that (a) these operations
were intensely monitored by observers and satellite
VMS (Vessel Monitoring System) and (b) that the
data generated on commercial stocks, fishing and
processing technology, and international market opportunities were made available to the government in
order to subsidize a national policy on fishing in deep
and oceanic areas. From 2000 onwards, unprecedented
commercial exploration began of fishing grounds 200
to 1000 m deep, revealing the existence of profitable
resources, efficient technologies, and international
market demands (Perez et al., 2003). During the past
six years, however, deep-water fishing has also come
into conflict with traditional fishing practices and
raised great concerns as to the sustainability of fragile
stocks and deep ocean habitats as a whole.
The present review intends to describe the development of the deep-water fishery off the Brazilian
coast from biological, economic, and political perspectives, addressing the lessons learned in this new
phase of Brazil’s fishing history and analyzing its
prospects for the future.
MONITORING AND DATA SOURCES
The deep-water fishery developed off the coast of
Brazil could possibly be the most intensely monitored
fishing activity in the country. Besides the use of official data collection instruments (i.e. logbooks), observers and VMS programs were implemented for the
first time in order to enforce the legal obligations of
the chartered fleet. These programs were formerly
structured and conducted as part of a scientific cooperation agreement established between the Brazilian
government and the University of “Vale do Itajaí”
(Santa Catarina, southern Brazil). In 2005, after a
period of development and adjustments, these programs have become national policies and are incorporated into the agenda of the Special Secretariat of
Aquaculture and Fishery, the Ministry of the Environment and Natural Resources, and the Brazilian
Navy.
Between 2000 and 2007, 311 fishing trips of the
chartered fleet were fully observed and monitored by
satellite VMS. Data on fishing position, depth, and
515
catch/bycatch from over 35,800 fishing sets conducted
by trawlers, bottom gillnetters, bottom longliners, and
potters were recorded and stored in a data bank (Table
1). Observers also collected biological samples of
these catches and recorded biometric data (size, sex,
and maturity, depending on the species) for around
713,810 individuals of the main target species (Table
1). Supplementary data was obtained during the same
period from landings of deep-water operations conducted in the harbors of Santa Catarina State by the
national fleet as reported by skippers in logbooks or
during harbor interviews at the time of the landings.
These data were extracted from the Santa Catarina
State
industrial
fishing
statistical
service
(www.univali.br/gep) and included biometric data
taken from national gillnetters, stern trawlers, and
double rig trawlers. Parallel sources of fishing and
biological data have also originated from surveys conducted as part of the REVIZEE program (e.g., Cergole
et al., 2005; Costa et al., 2005; Rossi-Wongtschowski
et al., 2006) and fishery statistical systems operated in
the states of Rio Grande do Sul, São Paulo, and Rio de
Janeiro.
Because deep-water fishing activity off the Brazilian coast is relatively recent, fishing data time-series
have been of limited use for stock assessments. This
limitation has been compensated, however, by the
availability of a robust geo-referenced catch, effort,
and biological data base provided by observed commercial operations and scientific surveys. In addition,
in the laboratory, biological samples have further provided detailed information on the reproduction, age,
and growth of some studied species. This combination
of information has been critical for building an empirical framework for recommending, discussing, and
implementing management plans for deep-water resources (Anon, 2005, 2006b, 2007).
DEEP-WATER FISHING GROUNDS
The continental margin off the Brazilian coast has
been subdivided into five sectors: northern, northeastern, central, southeastern, and southern (Fig. 1)
(Rossi-Wongtschowski et al., 2006). The continental
shelf is wider in the northern, southeastern, and southern sectors, where it has been intensely occupied and
exploited by traditional demersal fisheries (mostly
trawling) during the past 40 years (see Haimovici et
al., 2006a for review). Deep-water fishing activities
have concentrated on the slope grounds of the southeastern and southern sectors. This area is highly undulated and morphologically characterized by the occurrence of several seaward protrusions and submarine
canyons between 100 and 1000 m depth (Figueiredo
Jr. & Madureira, 2004). The depth gradient is gentle
(1:132 – 1:190) along a large central feature known as
the Brazilian Bight between 29°S and 24°S, becoming
steeper north of 23°S (1:10) and south of 32°S (1:13)
(Figueiredo Jr. & Tessler, 2004) (Fig. 1). The slope
floor is generally covered by mud, but there are areas
where nodules of calcareous algae and beach rocks
concentrate, predominantly north of 26°S. In addition,
deep-water coralline reefs have been mapped along
the lower slope of southeastern sector (20°-24°S),
some of them hundreds of meters long, tens of meters
wide, and up to 15 to 20 m high (see Pires, 2007 for
review).
Seamounts have been of secondary importance for
deep-water fishing activity off the Brazilian coast.
These structures ascend from the slope and ocean
basin floor throughout the Brazilian EEZ (RossiWongtschowski et al., 2006). Particularly dense and
accessible seamount concentrations are found in the
central and northeastern sectors, most notably as part
of the Ceará Plateau, Fernando de Noronha Chain, and
Vitória-Trindade Chain. Hand-line fishing and trawling have been reported on seamounts of these chains
(Fonteles-Filho & Ferreira, 1987; Martins et al., 2005;
Clark et al., 2007). In 1982-1984 and 2000-2002,
Soviet/Russian vessels also reported trawling on seamounts of the Rio Grande Rise area, outside the Brazilian EEZ (Clark et al., 2007).
FLEET DYNAMICS
Deep-water fisheries off Brazil rely on four basic fishing gears: hook-and-line (operated as hand-lines, vertical lines, and long-line settings), bottom gillnets,
pots, and bottom trawls (Perez et al., 2003). The national fleet participated in the occupation of deep areas
basically with longliners and trawlers, the former a
practice recorded almost along the entire Brazilian
coast at least since the 1960s (Peres & Haimovici,
1998) and the latter expanding to slope grounds by the
end of the 1990s (Perez et al., 2001) (Table 2). Chartered vessels operated with both gears mentioned
above but also introduced the use of deep-water gillnets and traps in the Brazilian EEZ (Perez et al., 2003;
Wahrlich et al., 2004). Besides fishing technology, the
deep-water chartered vessels also introduced other
novel technological practices to the national vessels,
including on board fish handling, processing, packing,
and freezing (Wahrlich et al, 2004). Absorbing these
practices were also important steps allowing the national industry to access EU and Asian seafood markets in the short term (Soares & Scheidt, 2005). Chartered fishing operations intensified from 2000 onwards, becoming gradually scarce between 2004 and
516
Table 1. Summary of Brazilian deep-water fishing data collected between 2000 and 2007. Chartered fleet data were collected by on board observers for all the
fishing operations conducted during this period. National fleet data originated from logbooks and interviews with skippers in the harbors of Santa Catarina State.
S. trawl: stern trawl; D.R. trawl: double rig trawl. * data from the national fleet includes coastal and deep-water resources.
Tabla 1. Resumen de los datos de pesca en aguas profundas de Brasil, obtenidos entre 2000 y 2007. Los datos de la flota arrendada fueron obtenidos por observadores a bordo en todas las operaciones de pesca realizadas en ese periodo. Los datos de la flota nacional provienen de las bitácoras de pesca y entrevistas a los
capitanes de buques pesqueros en los puertos del Estado de Santa Catarina. S. trawl: arrastreros por popa; D.R. trawl: arrastreros duplos. *datos de la flota nacional que también incluye capturas de recursos costeros.
Chartered fleet
Fishing Gear
Number of vessels
National fleet
Total
Pot
Gillnet
Longline
S. trawl
Total
Gillnet
S. trawl
D.R. trawl
Total
8
10
4
15
37
11
42
374
416
453
Number of monitored trips
111
79
7
114
311
122
878
10,840
11,718
12,029
Number of monitored hauls
10,037
3,947
476
21,400
35,860
-
-
-
-
35,860
Total landed catch (t)*
6,601
5,770
300
8,988
21,659
1,411
32,054
146,726
180,191
201,850
Number of sampled inds.
-
157,656
-
55,268
212,924
4,492
1,238
11,237
16,967
229,891
Merluccius hubbsi
-
-
-
15,238
15,238
-
201
2,731
2,932
18,170
Urophycis mystacea
-
-
-
-
-
904
225
2,855
3,984
3,984
Zenopsis conchifera
-
-
-
20,769
20,769
-
-
-
-
20,769
-
-
190
-
190
-
-
-
-
190
Epinephelus nigritus
-
-
-
1,271
1,271
-
-
-
-
1,271
-
-
-
161,408
161,408
-
-
-
-
161,408
-
-
-
76,220
76,220
-
-
-
-
76,220
-
-
-
25,977
25,977
-
-
-
-
25,977
Chaceon notialis
65,645
-
-
-
65,645
-
-
-
-
65,645
Chaceon ramosae
126,518
1,543
-
1,988
130,049
-
-
-
-
130,049
-
-
-
4,119
4,119
-
787
4,492
5,279
9,398
29,162
742,972
Illex argentinus
Total (ton)
Source: UNIVALI
713,810
517
Figure 1. Continental margin off Brazil, SW Atlantic. a) northern and northeastern sectors, b) central, southeastern, and
southern sectors. Dots represent fishing hauls conducted by the chartered trawlers. Chartered gillnetters, potters, and
longliners operated in the same slope areas as those occupied by trawlers (see the lower map) but are not represented for
clarity.
Figura 1. Margen continental de Brasil, Atlántico sudoccidental. a) sectores norte y nordeste, b) sectores centro, sureste y
sur. Los puntos representan lances de pesca realizados por arrastreros arrendados. Los buques de pesca de la flota arrendada que operan con enmalle, nasas y palangres operan en la misma área que los arrastreros, representados en el mapa
inferior, pero no fueron incluidos para mayor claridad.
518
2007 as many foreign vessels moved away from the
Brazilian EEZ. During this period, slope areas were
shared by national and foreign vessels, the former
predominating since 2004 (Table 2).
Deep-water fishing operations of the national fleet
involved the occupation of the shelf break (100-250
m) and upper slope grounds (250-500 m) of the southeastern and southern sectors (Perez et al., 2002a;
Perez & Pezzuto, 2006). These patterns were attributed to the (a) depth-limitations of fishing gear operations, (b) proximity of traditional fishing grounds, (c)
proximity of known markets for the country’s large
urban centers (i.e. São Paulo, Rio de Janeiro), (d) limited autonomy at sea, (e) low-capacity fish conservation systems, and (f) latitudinal restrictions of fishing
authorizations. These factors did not influence the
chartered fleet, which, in contrast, was required to
occupy areas off the shelf break (> 200 m) and explored a variety of habitats in a wide latitudinal and
depth range (Fig. 2). In general, however, most operations concentrated south of 18°S; 96% of the hauls
were conducted in the central, southeastern, and
southern sectors (Table 3). Operations started off over
the shelf break in 2000, rapidly expanding to completely occupy the upper slope between 2001 and
2002. Thereafter, fishing began on the lower slope (>
500 m) grounds, where the majority of deep-water
fishing has taken place, centered on the 750 m isobath.
By the end of 2007, over 97% of all deep fishing hauls
conducted by chartered vessels off Brazil occurred
below 250 m depth; the lower slope (>500 m) was the
deep area most heavily exploited by foreign vessels
(65.7% of conducted hauls) (Table 3).
Hook and line fishing
Hand-line fishing off Brazil was first a coastal activity
in the central sector, specifically off the southern coast
of Bahia State and the Abrolhos Archipelago (17°25'18°10'S, 38°33'-39°37'W). In the 1970s, the fleet expanded its activity towards the slope grounds of the
southeastern and southern coasts (200-600 m depth)
and changed its technology to vertical lines and finally
bottom long-line (Peres & Haimovici, 1998). By the
end of the 1990s, hand-line and long-line fleets were
operating on slope grounds to the north and south of
29°S, respectively. The former targeted the tilefish
(Lopholatilus villarii), snowy grouper (Epinephelus
niveatus), sandperch (Pseudopercis numida), and
catfish (Genidens barbus); whereas the latter targeted
mainly the wreckfish (Polyprion americanus), but also
produced important catches of Brazilian codling
(Urophycis mystacea), red porgy (Pagrus pagrus), and
pink cusk-eel (Genypterus brasiliensis) (Ávila-daSilva & Arantes, 2007; Haimovici et al., 2007).
Four chartered long-line vessels operated off the
southern sector of the Brazilian EEZ, three of them in
2000 and one between January and June of 2001 (Table 2). A total of 476 hauls were conducted during
seven fishing trips, all of which targeted wreckfish
concentrations south of 30°S and between 159 and
800 m (Fig. 2). In addition, these trips also landed
important catches of pink cusk-eel, the school shark
(Galeorhinus galeus), and tilefish (Table 4) (Perez et
al., 2003). Because the national long-line fleet already
heavily exploited wreckfish fishing grounds, regulations were implemented in 2001 that forced these
vessels to explore deeper areas of the lower slope. The
enforcement of these regulations stimulated foreign
longliners to abandon the Brazilian EEZ within the
year.
Bottom gillnet fishing
Deep-water gillnets were introduced in Brazil following similar experiences conducted off east Canada in
the early 1990s (Kulka & Miri, 2001) and principally,
the “rascos” operations in the deep areas of the NW
Iberian Peninsula and Cantabric Sea (Bruno et al.,
2001). The fishery started off in 2001 with two vessels
and increased to a maximum of ten in 2002, most of
them originating from Spain (Wahrlich et al., 2004)
(Table 2). These vessels conducted 79 fishing trips
(3,947 hauls), quickly occupying the upper slope
grounds, between 200 and 500 m depth along the entire southeastern and southern sectors of the Brazilian
coast (Fig. 2) (Perez et al., 2002a). The monkfish
Lophius gastrophysus was the targeted species, representing numerically 40.7% of the entangled organisms. Catches of royal crabs (Chaceon ramosae), spider crabs (Majidae), beard fish (Polimixia lowei),
silvery John dory (Zenopsis conchifera), Brazilian
codling, Argentine hake (Merluccius hubbsi), wreckfish, angel shark (Squatina argentina), and various
skates (Rajidae) were also important and, except for
monkfish, most were discarded (Perez & Wahrlich,
2005).
In mid-2002, following the preliminary assessments of monkfish and innumerable conflicts with
national trawlers, government regulations prohibited
foreign gillnetters to operate south of 21°S. That action defined the termination of chartered gillnet operations off Brazil, although a small national fleet continued the fishery. Composed of no more than five licensed units, this fleet assimilated the fishing technology and the international markets introduced by the
chartered vessels (Wahrlich et al., 2004).
519
Table 2. Temporal distribution of national and foreign (chartered) deep-water fishing activity off Brazil. Slope trawling
has been fragmented into shelf break, upper slope, and lower slope operations.
Tabla 2. Distribución temporal de la actividad pesquera en aguas profundas realizadas por la flota nacional y extranjera
(arrendada) en Brasil. Los arrastres en el talud fueron clasificados como operaciones efectuadas en el borde de la plataforma y en el talud superior e inferior.
Only national vessels
Only foreign vessels
1980-1990
1998
1999
2000
National + foreign vessels
2001
2002
2003
2004
2005
2006
2007
Longline
Gillnet
Pot
Trawl- shelf break
Trawl- upper slope
Trawl- lower slope
Pot fishing
The first episode involving pot fishing for deep-water
crabs was recorded in 1984-1985, when two chartered
Japanese vessels operated off the southernmost extreme of the Brazilian EEZ (Lima & Branco, 1991).
This activity began again in 1998 when another Japanese vessel initiated operations in precisely the same
area as part of the government-induced chartering
program (Perez et al., 2003). On both occasions, the
species targeted was the red crab (Chaceon notialis), a
stock whose distribution extends southwards to Uruguayan waters, where a similar pot fishery has existed
since the 1990s (Defeo & Masello, 2000). The same
single vessel continued to exploit the red crab off Brazil until 2007, operating on the upper and lower slope
(200 to 900 m depths) south of 33°S (Pezzuto et al.,
2006a).
Figure 2. a) Latitudinal and b) depth distribution of hauls
conducted by the chartered vessels on slope areas off
Brazil from 2000 to 2007. LS: lower slope, US: upper
slope, SB: shelf break.
Figura 2. a) Distribución latitudinal, y b) batimétrica de
los lances de pesca realizados por buques arrendados en
las áreas del talud de Brasil en el periodo 2000-2007. LS:
talud inferior, US: talud superior, SB: borde de la plataforma.
Between 2001 and 2002, another four chartered pot
vessels initiated their operations off southern Brazil
flying the flags of Russia, Spain, and the UK. These
vessels directed their efforts at another deep-water
crab, the royal crab (Chaceon ramosae); concentrations of this resource had been revealed by incidental
gillnet catches on board chartered vessels in 2001
(Perez & Wahrlich, 2005). Operations concentrated on
the lower slope (500-900 m depth) within a major
fishing area bounded by the parallels 27°S and 30°S
(Fig. 2). In 2003, this area was expanded northward
with the establishment of a new fishing ground off
southeastern Brazil between 19°S and 25°S. Said expansion coincided with the entry of another two vessels from Spain and one from the USA, increasing the
royal crab chartered pot vessel fleet to a maximum of
520
Table 3. Spatial distribution of deep-water fishing hauls conducted by the foreign chartered fleet off Brazil between 2000
and 2007. Hauls are grouped by fishing gears, depth strata (and seamounts), and sectors of the Brazilian coast. Numbers
in parentheses represent the proportion (%) of hauls conducted by gear in each depth strata and sector. In the last line, the
number in parentheses represents the proportion of hauls conducted by fishing gear.
Tabla 3. Distribución espacial de los lances de pesca en aguas profundas realizados por la flota extranjera arrendada en
Brasil entre 2000 y 2007. Los lances fueron agrupados según método de pesca, estratos batimétricos (y montes submarinos) y sectores de la costa de Brasil. Los números entre paréntesis representan el porcentaje (%) de lances realizados por
método de pesca en cada estrato batimétrico y sector. En la última línea los números entre paréntesis representan proporciones de lances realizados de acuerdo al método de pesca.
Longline
Gillnet
Pot
Trawl
Total
6
(13.0)
9
(19.6)
28
(60.9)
0
(0.0)
37
(1.1)
3186
(92.3)
230
(6.7)
0
(0.0)
4
(0.1)
628
(9.5)
5925
(90.0)
0
(0.0)
612
(2.7)
5634
(24.8)
15360
(67.7)
965
(4.3)
659
(2.0)
9457
(28.9)
21543
(65.7)
965
(2.9)
0
(0.0)
0
(0.0)
0
(0.0)
4
(8.7)
42
(91.3)
46
(0.1)
0
(0.0)
6
(0.2)
10
(0.3)
2294
(66.4)
1143
(33.1)
3453
(10.5)
19
(0.3)
57
(0.9)
292
(4.4)
4498
(68.3)
1715
(26.1)
6581
(20.1)
55
(0.2)
1221
(5.4)
3850
(17.0)
17438
(76.9)
123
(0.5)
22687
(69.2)
74
(0.2)
1284
(3.9)
4152
(12.7)
24134
(74.0)
3023
(9.2)
32767
(100.0)
Depth strata
Shelf break
(100-250) m
Upper slope
(250-500) m
Lower slope
(> 500) m
Seamounts
Coastal sector
North
Northeast
Central
Southeast
South
Total
seven units operating simultaneously off Brazil. In the
following four years, all the vessels exploited both the
southeastern and southern fishing grounds but gradually abandoned Brazilian waters by 2007. Altogether,
the chartered pot fleet operating on the southeastern
and southern Brazilian slope (on both Chaceon species) totaled eight vessels that conducted 111 fishing
trips and completed 10,037 hauls (Table 1).
From 1999 to 2007, national vessels attempted the
pot fishery for deep-water crabs on two known occasions. The first was in 2004-2005 and took place off
southern Brazil on board one vessel built for deepwater crab fishing; this attempt ended abruptly with a
wreck. Another incursion has been reported since
2006 off the coast of Ceará in the northeast sector of
the Brazilian coast. There, one vessel formerly used
for coastal lobster fishing has presumably exploited a
third species of the genus Chaceon, the golden crab C.
fenneri, at depths of 600 to 800 m (Carvalho et al.,
2009).
Trawl fishing
Trawling on the slope areas off Brazil intensified since
1999 as a consequence of both the expansion of traditional fishing areas of the national fleet and the operation of foreign trawlers chartered to explore deep
grounds within the Brazilian EEZ (Perez et al., 2001,
2003). Together, both national and foreign trawlers
have concentrated their efforts in the southern and
southeastern sectors of the Brazilian coast, exploiting
Figure 3. Bathymetric distribution of hauls conducted by
chartered vessels on slope areas off Brazil by year from
2000 to 2007. LS: lower slope, US: upper slope, SB:
shelf break.
Figura 3. Distribución batimétrica de los lances de pesca
realizados anualmente por buques arrendados en las áreas
de talud de Brasil, años 2000 a 2007. LS: talud inferior,
US: talud superior, SB: borde de la plataforma.
three discrete bathymetric strata: shelf break, (100-250
m), upper slope (250-500 m), and lower slope (> 500
m) (Perez & Pezzuto, 2006; Perez et al., 2009a) (Table 2).
National trawlers used two types of trawl gear on
the slope grounds: the double rig trawl traditionally
used in the pink shrimp fisheries on the continental
shelf and the stern trawl conducted by modified double rig trawlers and designed specifically to operate in
deeper areas (Perez et al., 2002a; Perez & Pezzuto,
2006). Between 2001 and 2003, landings from 1,511
fishing trips conducted on slope areas off southeastern
and southern Brazil by 255 double rig trawlers and 44
stern trawlers were recorded in the harbors of Santa
Catarina State. In that period, these operations accounted for 27.8% of all fishing trips conducted with
both types of gears in the state and 41.8% of all
catches landed by them. The Argentine hake and Brazilian codling were the main targets of both types of
trawlers (Table 4). Monkfish and the Argentine squid
have also been important catch components, the latter
restricted to winter months (July-September). Whereas
these species were dominant in catches obtained on
the upper slope, in shallower grounds of the shelf
break, the catches were highly multispecific and in-
521
cluded a variety of shellfish, finfish, and elasmobranchs, namely soldier shrimps (Plesionika spp.),
flounders (Paralichthys isosceles, P. triocellatus),
pink cusk-eel, and deep-water skates (Table 4).
A fleet composed of 37 chartered trawlers operated
on deep areas off the Brazilian coast since 2000, completing, by 2007, 311 fishing trips and 35,860 trawls at
depths of 100 to 1,173 m in the northern, northeastern,
southeastern, and southern sectors of the Brazilian
coast (Tables 1 to 3).
In southeastern and southern Brazil, a preliminary
“exploratory phase” of chartered trawling was established between late 2000 and mid-2001, when two
large vessels flying the flags of Portugal and the Republic of South Korea conducted long fishing trips
between 100 and 400 m depth (Perez et al., 2003;
Perez et al., 2009a). By the end of 2001, the results of
the preliminary exploration gave way to an “upper
slope directed phase” characterized by the intense
exploitation of two latitudinal strata, 23°S-25°S and
26°S-29°S, both between 250 and 400 m deep. This
phase included the operations of seven trawlers, most
of them originating from Spain, that targeted Argentine hake concentrations on the upper slope off southeastern Brazil. Catches of the Argentine squid were
also particularly important in this period, along with
the monkfish, silvery John dory, and Brazilian codling, the latter usually discarded due to the lack of an
international market (Table 4). After sharing the upper
slope and most of its demersal resources with the national fleet for nearly one year, most chartered trawlers left Brazilian waters by the end of 2002 (Perez et
al., 2009a).
Chartered trawling off Brazil continued, however,
through the operation of another set of foreign vessels
that established a third and still ongoing fishing phase
directed at the lower slope and valuable concentrations
of aristeid shrimps: Aristaeopsis edwardsiana (scarlet
shrimp), Aristeomorpha foliacea (giant red shrimp),
and Aristaeus antillensis (“alistado” shrimp) (Table 4)
(Pezzuto et al., 2006b; Perez et al., 2009a). Two Spanish trawlers initiated this phase in late 2002-2003,
establishing an intense fishing regime in a limited area
bounded by the 24-26°S parallels and 700-750 m isobaths. In mid-2004, another five trawlers from Spain,
Mauritania, and Senegal started operations within the
same limited area mentioned above, moving gradually
to new productive grounds to the north (19°30’-20°S)
and, in 2005, to the south of 26°S (Pezzuto et al.,
2006b; Dallagnolo et al., 2009). This phase directed at
the lower slope was the longest to be sustained by
chartered trawlers off Brazil, but it also declined in
2007 when most vessels abandoned Brazilian waters
due to poor catch rates. Throughout this phase,
522
Table 4. Landing composition of deep-water fishing operations off Brazil. “Main target-species” are species that generally compose more than 10% of the landed biomass and are always listed as targets. “Secondary target species” are species that compose from 1 to 10% of the landed biomass. “Valued bycatch” are species that represent less than 1% of the
landed biomass but are generally retained for commercialization. Sources for landing composition of national longliners
and handliners: Ávila-da-Silva & Arantes (2007), Haimovici & Velasco (2007), and Haimovici et al. (2007).
Tabla 4. Composición de los desembarques correspondiente a las operaciones de pesca realizadas en aguas profunda en
Brasil. “Main target-species” son especies que componen más del 10% de la biomasa desembarcada y siempre son nombradas como “objetivo” de la pesca. “Secondary target species” son especies que componen el 1-10% de la biomasa desembarcada. “Valued bycatch” son especies que componen menos de 1% de la biomasa de los desembarques, pero que en
general son retenidos para su comercialización. Fuentes para la composición de los desembarques de barcos de palangre:
Ávila-da-Silva & Arantes (2007), Haimovici & Velasco (2007) y Haimovici et al. (2007).
Crustaceans
Chaceon fenneri
Chaceon notialis
Chaceon ramosae
Metanephrops rubellus
Plesionika longirostris
Scyllarides deceptor
Mollusks
Illex argentinus
Octopus vulgaris
Elasmobrachs
Atlantoraja, Dipturus spp.
Carcharhinus spp.
Galeorhinus galeus
Isurus oxyrinchus
Rhinobatos spp.
Squalus spp.
Squatina argentina
Teleosts
Conger orbignyanus
Cynoscion guatucupa
Epinephelus nigritus
Epinephelus niveatus
Genidens barbus
Genypterus brasiliensis
Helicolenus dactylopterus
Lopholatilus villarii
Merluccius hubbsi
Micropogonias furnieri
Mullus argentinae
Pagrus pagrus
Paralichthys spp.
Polimixia lowei
Prionotus punctatus
Pseudopercis spp.
Trichiurus lepturus
Umbrina canosai
Urophycis mystacea
Zenopsis conchifera
Valued bycatch
pe
r
er
s
lop
e
slo
pe
Up
S
pe
Chartered tern
rs
tra
lo p
wl
e
-L
Ste
ow
Chartered rn
er
tra
slo
wl
pe
-S
ea
mo
u
National Gil
nt
ln e
t
Chartered Gill
ne
t
Secondary target-species
Chartered Pot
Chartered
National
Lo
Lo
ng
li
ne
ne
nd
li
National Ha
ng
lin
e
l-
raw
rn
t
Chartered
National
Ste
Tra
w
l-
Up
Up
p
l-
bre
ak
rn
National
Ste
DR
tra
w
Sh
e lf
lTra
w
DR
National
National
Ste
rn
t
raw
l-
Sh
e lf
bre
ak
Main target-species
two national trawlers, one imported and another
adapted to slope trawling, were also recorded in the
fishing areas off southeastern Brazil.
Chartered deep-sea trawling was also attempted in
the northern and northeastern sectors of the Brazilian
coast. Nearly 226 trawls were conducted between 428
and 1,158 m deep off the coast of Amapá State (4750°W) in late 2002, where productive concentrations
of A. edwardsiana and A. antillensis were found
(Pezzuto et al., 2006b). Additionally, a few trips by
one chartered trawler were directed towards the flat
tops of the seamounts making up the Ceará Plateau
and Fernando de Noronha Chain. These seamounts
rise from nearly 1,000 m at the base to 200 m at the
top, where the gentle topography was found suitable
for trawling. Catches in these areas were mostly composed of the Warsaw grouper (Epinephelus nigritus),
whose catch rates decreased rapidly to unprofitable
levels (Table 4). These areas have been abandoned
ever since (Perez et al., 2009a).
Other fisheries
In 2003, a national pot fishery directed at the common
octopus Octopus vulgaris developed in the southeastern sector of the Brazilian coast, with a maximum of
29 vessels operating in 2005. This fleet decreased to
around 14 units in 2007, but substantial activity of
illegal vessels has been reported, mostly off southern
Brazil. Pot operations have concentrated on the outer
shelf, although a considerable proportion of catches
have originated from shelf-break areas (100-200 m
deep) (Ávila-da-Silva & Tomás, 2007).
In 2005, one vessel chartered for squid jigging conducted one experimental trip off southeastern and
southern Brazil. This attempt was highly unsuccessful
but may have been affected by the fact that the vessel
did not operate during the winter months (JulySeptember), when trawl catches of Argentine squid
are highest (Perez et al., 2009a).
FISHERIES DEVELOPMENT AND
SUSTAINABILITY
Considering the year 2000 as a the reference for the
start of a deep-sea fishing phase in Brazil, total landed
catches of the main demersal “deep-sea” resources
reported for the southeastern and southern sectors of
Brazil, where this activity has concentrated, varied
annually from 5,756 ton in 2000 to a maximum of
19,923 ton in 2002, decreasing to nearly 11,000 ton in
2006 (Table 5). These annual figures have represented
2 to 8% of the total catch landed annually in this pe-
523
riod (Valentini & Pezzuto, 2006). In this section, the
main deep-water resources exploited off Brazil are
presented along with existing descriptive information
on historical catches (Table 5), abundance patterns
and stock assessments (Table 6), and management/conservation measures (Table 7).
Wreckfish, Polyprion americanus (Bloch &
Schneider, 1801)
The wreckfish is a large-sized serranid that constituted
the main target of the hook-and-line fisheries, particularly those established between 100 and 500 m deep
south of 30°S. Sparse catch records of this species
date back to 1973, but a series of nominal catches has
been available from 1986 onwards (Valentini &
Pezzuto, 2006). Until 2004, annual reported landings
oscillated around 700 to 800 ton (Table 5). These
figures, however, may not be totally realistic considering that landing records may be contaminated by two
other serranids (Epinephelus niveatus and E. flavolimbeatus) and that there has been a historical trend of
unreported catches, particularly during the first half of
this period (Haimovici & Peres, 2005). These authors
estimated that landings declined nearly 79% since
1989 (dropping from 2,200 ton in that year to less than
460 ton in 2002), in association with abundance reductions ranging from 57 to 94%, according to CPUE
time-series analysis. Part of this reduction has been
attributed to a significant increment in fishing mortality during the 1990s as the result of (a) the rising demands of international markets and (b) increased fishing power through the dissemination of the use of
long-line settings in the fleet.
The species is long-lived. Catches include females
and males as old as 76 and 62 years, respectively.
Maturation is reached for the first time after nine to 10
years-of-age in both sexes and spawning occurs on
localized areas off southern Brazil (Peres & Haimovici, 2003). In these areas, most of the local stock
is highly vulnerable to the long-line directed fishery as
well as unintentional mortality from slope trawling
and monkfish gillnetting (Peres & Klippel, 2003;
Perez & Wahrlich, 2005). Given the combination of
these K-strategy features and the important biomass
reductions mentioned previously, the Brazilian stock
has been included, justifiably so, on the IUCN “red
list” and Brazilian authorities imposed a moratorium
since 2005 (Tables 6 and 7) (Cornish & Peres, 2003).
Monkfish, Lophius gastrophysus Ribeiro, 1915
The monkfish is a lophiiform widely distributed along
the Brazilian shelf and slope. It is traditionally a valuable component of the catches obtained by double
524
Table 5. Annual landings (ton) of deep-water resources in southeastern and southern Brazil between 2000 and 2006.
Brazilian codling includes two species: Urophycis brasiliensis (coastal) and U. mystacea (deep-water).
Tabla 5. Desembarques anuales (ton) de recursos de aguas profundas en el sureste y sur de Brasil entre 2000 y 2006.
“Brazilian codling” incluye dos especies: Urophycis brasiliensis (costera) y U. mystacea (aguas profundas).
Species
2000
2001
2002
Year
2003
Total
2004
2005
2006
Teleosts
Brazilian codling Urophycis spp.
1,901.3 5,991.7 7,847.0 5,273.6 3,491.2 4,547.8 4,825.0 33,877.6
Tilefish
533.2
Argentine hake
Merluccius hubbsi
225.8 2,653.4 3,708.8 3,042.4 1,417.8 1,564.5 1,950.5 14,563.2
Silver john dory Zenopsis conchifera
Monkfish
Crustaceans
Royal crab
Chaceon ramosae
Red crab
Chaceon notialis
Scarlet shrimp
0.0
709.2
0.0
597.6
82.5
572.5
147.1
545.2
42.3
560.8
85.1
717.0 4,235.5
31.0
388.0
1,934.4 7,063.9 5,073.1 2,556.3 2,410.7 2,544.6 2,516.5 24,099.5
2.0
593.6 1,252.3
746.0
849.9
494.5
171.4 4,109.7
1,157 1,183.6 1.089.0 1,377.7 1,092.5
675.7
302.8 5,899.8
0.0
0.0
13.0
58.9
81.6
182.6
99.3
435.4
Giant red shrimp Aristaeomorpha foliacea
0.0
0.0
0.0
4.6
14.9
42.6
51.7
113.8
Alistado shrimp Aristeus antillensis
0.0
0.0
0.3
0.5
5.5
15.8
5.4
27.5
Molluscs
Argentine squid Illex argentinus
2.7
13.6 2,600.7
31.2
158.3
453.1
Total
292.5 3,552.1
5,756.4 18,209.0 19,923.0 13,810.8 10,109.9 11,167.1 11,028.1 91,302.1
Sources: IBAMA/DF, IBAMA/RJ, CEPSUL/IBAMA, CEPERG/IBAMA, IP-APTA and CTTMar/UNIVALI.
rig trawling along the coast of Rio de Janeiro State. In
2001, an important cycle of commercial exploitation
of the species began in Brazil and peaked in the following year, when over 150 trawlers and nine chartered vessels operating with bottom gillnets landed
7,094 ton (Table 5) (Perez et al., 2002a, 2003; Perez
& Pezzuto, 2006). This fishing regime continued during most the following year, with landings of 5,129
ton, but changed in 2003 as the chartered vessels
abandoned Brazilian waters. Since then, exploitation
has been maintained mostly by double rig trawlers
along with a few vessels of the national fleet transformed to fish with the new gillnet technology (Wahrlich et al., 2004). Landings decreased to roughly 50%
from 2002 to 2003, remaining stable around 2,500 ton
ever since (Table 5).
Through data collected from national and chartered
operations, catch-at-size, general linear models, and
depletion models were combined in order to provide
both pristine biomass and abundance index estimates
for 2001 (Table 6) (Perez et al., 2005). Landing statis-
tics indicated that fishing removed approximately 16%
of the 62,776 ton of total estimated biomass and approximately 32% of the spawning stock. Alternatively,
variations in the abundance indices suggested a more
severe 30-60% biomass reduction in the main fishing
grounds off southern Brazil throughout 2001. The
latter scenario was favored by the establishment of a
conservative reference point and the Gulland’s equation was used to predict a maximum sustainable yield
(MSY) of 2,500 ton per year, or nearly 4% of the total
biomass (Perez et al., 2002b). A later assessment
combining life-history parameters and population
models (Kirkwood et al., 1994; Perez, 2006) estimated
an MSY for the species of around 6% virginal biomass
and suggested that the former recommended annual
catch was conservative enough to sustain the fishery at
biologically safe levels. Notwithstanding, in 2002, as
biomass reductions in the fishing areas reached nearly
50% of the 2001 levels, a lower annual catch (1,500
ton, nearly 2.5% of the virginal biomass) was recom-
525
Table 6. Abundance estimators, methods for stock assessment, reference points, and the status of deep-water fisheries/stocks exploited in southeastern and southern Brazil. t: year, B0: virginal or initial biomass, C: catch, Cref: catch in the
year of reference, E: exploitation rate.
Tabla 6. Estimadores de abundancia, métodos de evaluación del stock, puntos de referencia y estado de las pesquerías de
aguas profundas/stocks explotados en el sureste y sur de Brasil. t: año, B0: biomasa inicial o virginal, C: captura, Cref:
captura en el año de referencia, E: tasa de explotación.
Stocks
Elasmobranchs
Galeorhinus galeus
Teleosts
Merluccius hubbsi
Urophycis mystacea
Zenopsis conchifera
Abundance estimators/
indicators
Stock assessment
methods
Reference points
(limits)
Stock
status
-
-
-
Risk of extinction (1)
Swept area (3),VPA,
Depletion, GLM (4)
Z; M; S (2)
Gulland’s equation
(4)
0.06B2001 (5); GLMt/GLM0;
GLMt/GLMMSY (4, 6)
Under-exploited (2)
Overexploited (4, 7)
VPA (8)
Swept area (3), GLM (7)
Thompson & Bell (8)
Kirkwood et al., 2004
(5)
F0,1; Fmax (8)
0.1B2002 (5)
Overexploited (8)
Fully exploited/
overexploited (5,7)
-
Ct/Cref;
CPUEt/CPUEref (10)
(5)
(5)
-
Colapsed (10)
0.1B2002 (5)
Fully exploited/
overexploited (9,5)
Unknown
Swept area (9,3),
GLM (7)
Swept area (3)
0.1B2002 (5)
Crustaceans
Bt/B0; Bt/BMSY;
CPUEt/CPUE0;
CPUEt/CPUEMSY;
GLMt/GLM0;
GLMt/GLMMSY (11)
Bt/B0; Bt/BMSY;
CPUEt/CPUE0;
CPUEt/CPUEMSY;
GLMt/GLM0;
GLMt/GLMMSY (11)
Bt/B0; Bt/BMSY;
CPUEt/CPUE0;
CPUEt/CPUEMSY;
GLMt/GLM0;
GLMt/GLMMSY (11)
Aristaeopsis
Edwardsiana
Swept area, GLM (11)
(11)
Aristaeomorpha
foliacea
(11)
(11)
Chaceon notialis
EFA, GLM, CPUE
(12, 13)
(12)
Bt/B0; Bt/BMSY; CPUEt/CPUE0; CPUEt/CPUEMSY; GLMt/GLM0;
GLMt/GLMMSY (13)
Fully exploited (13)
Chaceon ramosae
EFA, GLM, CPUE
(12, 8)
(12)
Bt/B0; Bt/BRMS; CPUEt/CPUE0; CPUEt/CPUERMS; GLMt/GLM0;
GLMt/GLMRMS (13)
Fully exploited/
Overexploited (13)
Illex argentinus
Swept area (14)
-
-
Unknown
Octopus vulgaris
VPAe (15, 16)
Bt/Catcht (16)
-
Under-exploited (16)
Overexploited (11)
Unknown
Unknown
Molluscs
(1) Vooren & Klippel (2005), (2) Bernardes et al. (2005b), (3) Haimovici et al. (2008), (4) Perez et al. (2005), (5) Perez
(2006), (6) Perez et al. (2002b), (7) Perez (2007a), (8) Ávila-da-Silva & Haimovici (2005), (9) Haimovici et al. (2006b),
(10) Haimovici & Peres (2005), (11) Dalagnollo (2008), (12) Pezzuto et al. (2006a), (13) Pezzuto et al. (2006b), (14)
Haimovici et al. (2006c), (15) Tomás (2002), (16) Tomás & Petrere Jr. (2005).
526
mended (Anon, 2007). This MSY was used to define a
TAC (Total Allowable Catch) as one of the elements
of a management plan discussed and agreed on by
fishing authorities in 2002-2003 (Table 7). This plan
also included the definition of a bottom gillnet fleet of
no more than nine units, a maximum of 1,500 nets per
vessel, 280 mm mesh size (stretched), and no-fishing
areas, among other measures (Perez et al., 2002b;
Anon, 2005).
Since the beginning of the monkfish production
cycle, however, landed catches have been systematically higher than the maximum recommended catches
(Table 5). That pattern is regarded to be the main
cause of the major biomass reduction in 2002 and the
stabilization at biologically insecure levels thereafter
(Perez, 2007a; Anon, 2007).
The monkfish was exploited throughout the southern and southeastern regions between the 100-600 m
isobaths. Brazilian trawlers concentrated their activities on the shelf break (at 100-200 m) and chartered
gillnet vessels in deeper areas of the upper slope (at
300-400 m). Because the stock size-structure is affected by the bathymetric gradient across the slope
and both fishing gears differ markedly in mesh-size,
trawler mortality concentrated on young, immature
specimens (mostly males), whereas gillnet fishing
tended to affect mostly large adult females, which are
dominant in areas deeper than 300 m. After 2002, as
chartered vessels no longer operated in the Brazilian
EEZ, the deep fraction of the stock tended to be less
affected than the one exploited by trawlers on the shelf
break (Valentim et al., 2007). In recent years, trawlers
targeting monkfish off southern Brazil have tended to
occupy deeper areas of the slope and to include large
individuals in their catch. These individuals also have
predominated in the catches of the small national gillnet fleet (Anon, 2007).
Argentine hake, Merluccius hubbsi Marini, 1933
The Argentine hake is a benthopelagic gadiform of the
family Merluccidae that occurs in the SW Atlantic
shelf and slope waters from 22° to 55°S. The highest
densities occur over the Patagonian Shelf where the
species has long sustained an important trawl fishery
(Bezzi et al., 2004). Catches in Brazilian waters have
mostly occurred in the southern sector and have been
historically associated with the northward penetration
of juveniles from the Patagonian stocks, particularly
during years when the influence of the cold Malvinas/Falkland Current waters in the Brazilian EEZ was
intense (Haimovici et al., 1994). From 1990 onwards,
important catches have been reported off the coast of
Rio de Janeiro State, in the southeastern sector; these
come from what appears to be a distinct stock whose
distribution is associated with the local upwelling of
cold South Atlantic Central Waters (Vaz-dos-Santos
& Rossi-Wongstchowski, 2005; Haimovici et al.,
2008). This “Brazilian” stock has constituted one of
the main targets of the slope trawling fishery conducted since 2000, both by national and foreign trawlers (Perez et al., 2003; Perez & Pezzuto, 2006; Perez
et al, 2009a). The species also appeared amongst the
most important components of the deep-water gillnet
catches obtained by the chartered fleet in 2001-2002,
although nearly 87% of these catches were discarded
in the monkfish-oriented operations (Perez & Wahrlich, 2005).
Annual landings through the 1980s and 1990s have
been mostly under 1,000 ton (Valentini & Pezzuto,
2006). In 2001, landings reached 2,653 ton, almost 10
times the levels recorded in the previous years, increasing to over 3,000 ton in 2002 and 2003 (Table 5).
Chartered trawlers contributed with 38.4% (1,018 ton)
and 52.7% (1,953 ton) of the total landings in 2001
and 2002 respectively. In 2003, nearly 90% of the
3,042 ton landed were produced by national double rig
trawler operations (Perez et al., 2009a). After 2003,
annual landings were cut in half and stabilized around
1,400-1,500 ton (Table 5).
Surveys conducted by the REVIZEE Program reported the highest densities between 250 and 550 m
depths and within two latitudinal strata: one in the
southernmost extreme of the Brazilian EEZ (33-34°S)
and another in the southeastern sector (23-25°S)
(Haimovici et al., 2008). The latter was the concentration primarily exploited by both national and foreign
trawlers, with the largest catches being obtained at
depths of 300 to 400 m (Perez & Pezzuto, 2006; Perez
et al., 2009a). A direct swept area assessment estimated a total of 21,924 ton (± 5,922.2 95%CI) of Argentine hake in the southeastern sector in 2002, and an
MSY of 2,215 ton (corresponding to 10% of the total
stock biomass) was estimated based on life-history
parameters (Table 6) (Haimovici et al., 2008; Perez,
2006). Between 2001 and 2003, catches were well
above the estimated MSY and the total biomass decreased nearly 50% from 2003 onwards (Perez, 2007a;
Anon,
2007).
Vaz-dos-Santos
&
RossiWongstchowski (2005) further demonstrated that
catches of the trawl fishery were highly concentrated
on immature males and females (1-2 years old). These
authors also estimated a 0.58 fishing mortality rate (F)
that clearly surpassed the FMSY levels as defined by
Perez (2006). All the above assessments converge into
a scenario of overfishing that calls for an urgent upper
slope trawling management plan (Table 7).
527
Table 7. Management elements of the deep-water fisheries in southeastern and southern Brazil. Logbooks and VMS: 100% coverage. Observers: 100% coverage. Exceptions are indicated in specific cases.
Tabla 7. Elementos utilizados en el manejo de las pesquerías de aguas profundas en el sureste y sur de Brasil. Bitácoras a bordo y VMS: 100% de cobertura.
Observadores: 100% de cobertura, Excepciones están indicadas en casos específicos.
Bottom longline
Double-rig trawl
(shelf break)
Bottom trawl
(upper slope)
Bottom trawl
(lower slope)
Gillnet
Trap
Trap
Trap
No
2008
2008
Now
implementing
2008
2008
2005
Now
implementing
Target and
accessory
species
Polyprion americanus (*);
Lopholatilus villarii;
Pseudopercis numida;
Epinephelus niveatus;
Urophycis mystacea;
Galeorhinus galeus;
Genypterus brasiliensis;
Multispecies (**)
Urophycis mystacea;
Merluccius hubbsi;
Zenopsis conchifera; Illex
argentinus
Aristaeopsis
edwardsiana;
Aristaeomorpha
foliacea; Aristeus
antillensis
Chaceon notialis
Chaceon ramosae
Chaceon fenneri
Fleet size
Unlimited
Unlimited among coastal
pink-shrimp trawlers
17
(< 600 HP)
2
9
2
2
1
Brazilian EEZ
18o20’ S to the Southern
limit of the Brazilian EEZ;
100-250 m depth
18o20’ S to the Southern
limit of the
Brazilian EEZ; 250-500 m
depth
18o20’ S to 28o30’;
500-1000 m depth
21o’ S to the Southern
limit of the Brazilian
EEZ; > 250 m depth
32o S to the Southern limit of the
Brazilian EEZ; >
200 m depth
19o S to 30o S; >
500 m depth
NE coast > 200 m
depth
Jan-Dec
March - May
Jan-Dec
Jan-Dec
Jan-Dec
Jan-Dec
Jan-Dec
Jan-Dec
1.500 ton.year-1
735 ton. year-1
420 ton.year-1
No
Management
plan
Area
Fishing
season
TAC
No
No
No
60 ton.year-1. Individual
(not-transferable)
quotas of 7.5
ton.trimester-1
Effort limits
No
No
No
No
Up to 1000 nets.vessel1
(maximum net
length: 50 m)
No
Up to 900
traps.vessel-1
Minimum
legal sizes
Yes, species-specific
No
No
No
No
No
No
No
Gear
restrictions
No
Double-rig trawl
Stern trawl; minimum
cod-end mesh size 90 mm
stretched
Stern trawl; minimum
cod-end mesh size 60
mm stretched
Minimum mesh size
280 mm stretched;
nets tagged with vessel
register
Mesh size 120 mm
stretched; escape
panels; traps tagged
with vessel register
Mesh size 120 mm
stretched; escape
Mesh size 120 mm
stretched; escape
By-catch
limits
No
(5%); other coastal species*** (15% of the total
catch)
Chaceon spp. (5%);
(5%); Aristeidae shrimps
(1% of the total catch)
Chaceon spp. (15%);
(5% of the total catch).
Lopholatilus villari
(5%); Chaceon spp.
(5% of the total catch)
No
No
No
528
Exclusión
areas
Rotation of
harvestable
areas
Catch or
processing
limits
Control
SE and S (****)
Spawning
time/area:
August to
December; < 600
m depth
Spawning
time/area: January
to June; < 700 m
depth
No
No
SE and S (****)
SE and S (****)
SE (****); seamounts;
coral bottoms; areas N
of 21oS when catches
of A. antillensis attain
4.4 ton
No
No
No
N and S from the
exclusion area SE
No
No
No
No
No
No
No
No
No
Mutilation (only
claw processing)
prohibited
Mutilation (only
claw processing)
prohibited
Mutilation (only
claw processing)
prohibited
Logbooks; VMS
Logbooks; VMS;
Obser-vers (20%
coverage)
Logbooks; VMS;
Observers (50%
coverage)
Logbooks; VMS;
Observers
Logbooks; VMS;
Observers
Logbooks; VMS;
Observers
Logbooks; VMS;
Observers
Logbooks; VMS;
Observers
* Under moratory.
** Plesionika spp., Parapenaeus americanus; Rioraja agassizzi; Altantoraja cyclophora; A. castelnaui; A. platana; Sympterygia bonapartei; S. acuta; Genypterus brasiliensis; Paralichthys isosceles; P. triocellatus; Illex argentinus; Metanephrops rubellus; Mullus argentinae; Polymixia lowei; Helicolenus dactylopteru; Zenopsis conchifera.
*** mainly Cynoscion striatus; Micropogonias furnieri; Umbrina canosai and Macrodon ancylodon.
**** Exclusions areas named SE and S are defined, respectively, by the following coordinates: 23o40'S/44o00'W-24o15'S/45o00'W-24o26'S/43o30'W-25o0 0'S/44o30'W and 29o00'S/48o35'W29o00'S/47o40'W-30o00'S/49o20'W-30o00'S/47o40'W.
Brazilian codling, Urophycis mystacea (Ribeiro,
1903)
The Brazilian codling is another gadiform of great
importance for the development of a deep-water fishery off Brazil. The species occurs over the slope
throughout the entire latitudinal range of the southeastern and southern sectors of the Brazilian coast.
High densities have been reported south of 30°S,
where the species concentrates below the 150 m isobath, and also in some areas to the north of 30°S, although always deeper than 300 m (Haimovici et al.,
2008). This gadid was a major target of slope trawling
conducted by national vessels between 2001 and 2003,
contributing 30.7% and 17.8% of the catches landed
by double rig and stern trawlers, respectively (Perez &
Pezzuto, 2006). Its proportion in the catches tended to
be even higher on trips conducted in areas deeper than
250 m south of 29°S. In the catches of chartered
trawlers, U. mystacea was regarded as incidental,
possibly because operations were concentrated in the
northern extreme of the southeastern sector of the
Brazilian coast, an area where the species is less
abundant (Perez et al., 2009a). In addition, most chartered trawlers have usually discarded this species as it
lacked international markets. Between 1997 and 1998,
Haimovici & Velasco (2007) reported that the Brazilian codling was relatively important in the landings of
the long-line fleet operating off southern Brazil, pointing out that catches could be even higher than the
figures recorded at the landings since the species was
frequently used as bait for higher-priced species such
as the wreckfish. In fact, the species was among the
most abundant in the catches with long-lines, vertical
lines, and traps conducted on the slope off southern
Brazil under the REVIZEE program and also in commercial catches obtained by chartered longliners in
2000-2001 (Perez et al., 2003; Haimovici et al., 2004;
Bernardes et al., 2005a). In the chartered gillnet fishery for monkfish, the Brazilian codling was one of the
major components, although less than 25% of these
catches were estimated to be actually retained and
processed (Perez & Wahrlich, 2005). Recently, as the
national deep-water gillnet fishery for monkfish expanded to deeper areas of the slope, catches of U.
mystacea have also increased and been landed as valuable bycatch. The species is undoubtedly one of the
most abundant components of the demersal habitats of
the slope off southeastern and southern Brazil, and it
is also one of the most intensely fished, both intentionally and non-intentionally, by several fishing
methods (Haimovici et al., 2006a).
Landed catches of the Brazilian codling have been
historically pooled with those of a shallow-water cogeneric species: U. brasiliensis (Valentini & Pezzuto,
529
2006). Nevertheless, a three-fold increase in the landings recorded since 2001 has been attributed to
catches of the slope form (U. mystacea) as a consequence of the trawl fishery’s expansion to deeper areas (Perez & Pezzuto, 2006). Total landings oscillated
between 5,000 and 7,000 ton between 2001 and 2003,
declining in the subsequent years (Table 5). Estimates
derived from the landing composition in the harbors of
Santa Catarina State, where U. mystacea has been
found since 2003, indicate that between 70 and 80%
of these figures correspond to catches of this species.
Following the same estimation procedures previously described for the Argentine hake, an MSY of
1,182.4 ton has been estimated for this species, that is
9.5% of the total biomass available in fishing areas of
southeastern and southern Brazil in 2002 (12,446 ton
± 4,605.0 ton 95% CI) (Perez, 2006; Haimovici et al.,
2008). Even considering that reported landings overestimate U. mystacea total catches (see above), it has
been demonstrated that these have greatly surpassed,
at least since 2001, the limits estimated as potentially
sustainable (Table 6) (Anon, 2007). Significant biomass reductions have been observed in 2004-2005,
possibly as the outcome of an unsustainable fishing
regime (Perez, 2007a). Similar conclusions have been
drawn by Haimovici et al. (2006b), who argued that
the species was probably subjected to excessive exploration rates (0.5-0.6) in 1997-1998, even before the
slope trawling expansion in Brazil. The species is to
be considered, along with the Argentine hake, in the
upper slope trawling management plan (Table 7).
Silvery John dory, Zenopsis conchifera (Lowe,
1852)
This benthopelagic zeiform is distributed in shelf
break and slope areas worldwide. Fishing surveys
conducted off southeastern and southern Brazil since
the 1970s have indicated a moderate potential for
commercial exploitation, although this is generally
hampered by the uncertain availability of favorable
markets for this species (Haimovici et al., 1994). The
recent survey conducted under the REVIZEE program
revealed that the species is concentrated at depths of
200 to 400 m, particularly in two latitudinal strata: 2930°S and 23-25°S (Haimovici et al., 2008). Commercial catches were recorded for the first time in those
areas by chartered trawlers during the 2000-2001 exploratory phase (Perez et al., 2003; Perez et al.,
2009a). After that, in general, the species was still
caught abundantly by these trawlers although it was
usually discarded (Perez et al., 2009a). This may also
have contributed to the small volumes recorded at the
landing sites of the national trawlers that operate on
the slope grounds (Table 5).
530
In 2002, the biomass and calculated MSY were
38,876 ton (± 24491.9 ton 95% CI) and 4,895.5 ton
(12.5% of total biomass), respectively (Table 6)
(Perez, 2006; Haimovici et al., 2008). Whereas landings indicate that the stock has been largely underexploited (Table 5), the indirect impact may be significant given the considerable biomass that was likely
discarded by national trawlers operating on the slope
off southeastern and southern Brazil, where the species is highly vulnerable (Haimovici et al., 1994;
Perez et al., 2009a). The species is also considered to
be a target in the upper slope trawling management
plan (Table 7).
Red crab, Chaceon notialis Manning & Holthuis,
1989
Following the development of a directed fishery in
Uruguayan waters since 1995 (Defeo & Masello,
2000), the exploitation of the red crab C. notialis
started in Brazil in 1998, when the Japanese factory
vessel Kinpo Maru No. 58 was chartered by a national
company. The vessel was closely monitored by observers and VMS since 2000, making available all the
fishing and biological data needed for describing and
analyzing this valuable, new deep-water fishery. Between 2000 and 2004, red crab catches oscillated
around 1,130 ton year-1 (Table 5) and were entirely
exported to Asia as frozen processed crabs. After attaining a maximum of 1,377.7 ton in 2003, catches
declined continuously until 2007, when the permit for
Kinpo Maru No. 58 was cancelled by the national
fishing authorities.
The application of the Effective Fishing Area
Method (Defeo et al., 1991; Arena et al., 1994) and
Gulland’s Formula (Pezzuto et al., 2002) for the “Brazilian” part of the stock (33°00’S and 34°40’S) allowed the virginal biomass and the MSY to be estimated at 17,117.8 ton (16,453.6-7,779.0 CI95%) and
1,027 ton per year, respectively (Table 6). A management plan for the red-crab fishery was established in
May 2005 (Pezzuto et al, 2006a) and included, inter
alia, a total allowable catch of 1,050 ton live weight
year-1, a maximum number of permits (2 vessels), and
a minimum mesh size of 110 mm (stretched) in the
pots (Table 7). Unregulated catches surpassed MSY in
most years (Table 5) and, therefore, by the end of
2005, the stock biomass was reduced to nearly 60% of
its original levels (Pezzuto et al., 2006a).
Females naturally contributed 67 to 77% of the
biomass exploited in Brazil and most of the catches
were composed of immature individuals. Spawning
seems to be localized both in space and time; in Brazil, ovigerous females were found concentrated at
depths lower than 600 m, mostly from July to Decem-
ber (Pezzuto et al., 2006b), following the same pattern
previously reported for Uruguayan waters (Defeo et
al., 1992). A review of the red crab management plan
has been recently agreed on and was implemented in
2008 (Table 7). The main changes in the original rules
include a TAC reduction to 735 ton year-1, a fishing
ban in areas shallower than 600 m during the second
half of the year, and a minimum mesh size in the pots
of 120 mm (stretched).
Royal crab, Chaceon ramosae Manning, Tavares &
Albuquerque, 1989
Unlike Chaceon notialis, which was exploited in Brazil by a single pot vessel, the fishery for Chaceon
ramosae started in 2001 and soon expanded to a fleet
of up to eight foreign processor vessels chartered by
national companies. The species was also the most
abundant and valuable bycatch item of several chartered gillnetters and trawlers that targeted other deepsea resources, namely monkfish and aristeid shrimps
(Perez & Wahrlich, 2005; Pezzuto et al. 2006c).
In the first year of exploitation, catches of royal
crabs summed 593.6 ton and exhibited a 2-fold increase in 2002 (Table 5). Catches declined in 2005
and 2006 as a direct response to lower catch rates and
successive reductions in the number of vessels in the
fishery, which was interrupted by the end of 2006
(Pezzuto et al., 2006b). In 2002, stock biomass and
MSY were estimated to be 11,636.4 ton (11,271.512,007.7 ton CI 95%) and 593.5 ton, respectively
(Table 6) (Pezzuto et al., 2002, 2006a). A management plan for the royal-crab fishery was only established in May 2005 and included, inter alia, a total
allowable catch (600 ton live weight year-1), a maximum number of permits (3 vessels) and pots per vessel (900 units), and minimum mesh size in the pots
(100 mm stretched) (Table 7). Delayed management
was critical for the species, as catches surpassed the
suggested TAC in most of the years and especially in
2002, when they were 211% higher than the MSY. In
2005, the stock biomass was reassessed at 44-48% of
the 2001 levels (Pezzuto et al., 2006b).
Males naturally predominated the catches and
ovigerous females were concentrated in areas shallower than 700 m from January to June (Pezzuto et al.,
2006b); more than 50% of the males and females
caught between 2001 and 2005 were sexually immature (Pezzuto & Sant’Ana, 2009). The management
plan for the royal crab fishery was recently reviewed
in light of the new findings regarding stock biomass
levels and biological characteristics of the species
(Table 7). The newly established measures include: a)
a 33% reduction, either in the TAC or the maximum
number of permits, b) the closure of areas shallower
than 700 m during the first half of the year in order to
protect ovigerous females from fishing, and c) increasing the minimum mesh size in the pots from 100 to
120 mm (stretched).
Golden crab, Chaceon fenneri (Manning &
Holthuis, 1984)
The golden crab Chaceon fenneri was first reported in
the Brazilian EEZ by Sankarankutty et al. (2001)
based on survey samples taken along the northeastern
coast (1.5-4.0°S; 34.0-42.0°W). Previously known
only in the northwestern Atlantic (Manning &
Holthuis, 1989), the species supports a directed fishery
in the United States (Erdman & Blake, 1988). Exploitation for golden crabs in Brazil has been very incipient as compared to royal and red crabs, supposedly
due to operational and/or commercial limitations experienced by most of the foreign vessels which, besides targeting the latter species, conducted some exploratory fishing on the northeastern coast as well. A
preliminary management plan has been recently discussed for this species, although adequate data on
distribution, fishing potential, and biological characteristics are virtually inexistent (Table 7). Most information on this stock has been made available very
recently, as fishing operations of a national pot vessels
that entered the fishery have been continuously monitored. Carvalho et al. (2009) summarizes the preliminary results of this study.
Scarlet shrimp, Aristaeopsis edwardsiana (Johnson,
1867)
The scarlet shrimp (carabinero shrimp) is an aristeid
shrimp distributed in slope areas worldwide. This is a
high-valued deep-water species that has been commercially exploited by trawl fisheries at low latitudes
of both the East and West Atlantic (Dallagnolo et al.,
2009). Off Brazil, it has been the main target of the
lower slope trawl fishery phase conducted by chartered vessels since 2003 (Pezzuto et al, 2006c; Perez
et al., 2009a). The main concentrations have been
exploited in the southeastern sector, between 22 and
26°S and from the 700 to 750 m isobaths. After 2004,
fishing exploration continued within these bathymetric
boundaries but expanded latitudinally to productive
areas in the central and southern sectors of the Brazilian coast. Concentrations were also identified in
northern Brazil, off the coast of Amapá State, where
fishing was mostly exploratory (Pezzuto et al, 2006c;
Perez et al., 2009a).
Annual catches increased from 13.0 ton in 2002 to
a maximum of 182.6 ton in 2005, declining to 19.9 ton
in 2007 (Table 5). Through the use of commercial
catch rate data and swept area procedures, a total ex-
531
ploitable biomass of 865.0 ton was estimated within
the fishing areas south of 19°S in 2002 (Table 6). This
biomass, regarded as virginal, was reduced by 41 to
49% by 2007 due to an intense trawling effort concentrated on spatially limited fishing grounds (Dallagnolo, 2008). Considerations of the species’ life-history
(Kirkwood et al., 1994) allowed the definition of an
MSY of around 6% of the virginal biomass or approximately 2.5 ton. Taking the total biomass at MSY
as a limit reference point, it was concluded that the
recent state of the scarlet shrimp stock has been biologically unsafe, demanding short-term restoration
management actions (Table 6).
Biological data have shown that males attain
smaller sizes (maximum 72 mm carapace length) than
females (maximum 106 mm carapace length). Sexual
maturity was reached at 57-59 mm and 47.7 mm carapace length in males and females, respectively. The
reproductive cycle is annual, with most activity concentrated in the second half of the year. The catch
size-structure was dominated by females and included
limited proportions (15-24%) of immature individuals
(Anon, 2007). A management plan for this fishery has
been recently proposed, including the other two
aristeid shrimps (see below) as target species but using
the scarlet shrimp fishing potential to limit annual
catches (Table 7) (Dallagnolo, 2008).
Giant red shrimp, Aristaeomorpha foliacea (Risso,
1827)
The giant red shrimp (moruno shrimp) was the second
most abundant aristeid shrimp caught by chartered
trawlers on the lower slope off Brazil (Pezzuto et al.,
2006c). Catches were generally associated with the
chartered trawling activity directed at the larger, more
abundant scarlet shrimp. Nevertheless, the species was
found to dominate catches in particular fishing
grounds of the southeastern and central sectors, principally in later years as densities of scarlet shrimp
decreased (Dallagnolo et al., 2009). Total giant red
shrimp catches increased continuously until 2005 and
2006, peaking at 42.6 and 51.7 ton, respectively, and
then declining to 7.7 ton in 2007 (Table 5).
Densities increased continuously on the slope off
southeastern Brazil from 2002 to 2007, as estimated
by commercial catch rate analysis. In this sector, the
mean exploitable biomass peaked in 2007 at 205.6 ton
(Dallagnolo, 2008). Off the central sector of the Brazilian coast, a maximum of 86.5 ton of exploitable
biomass was estimated in 2006, declining by approximately 46% in 2007, possibly in response to
harvest rates as high as 22-53.6% in 2005-2006. The
estimated MSY for the giant red shrimp was 15-19%
and 17-20% of the exploitable biomass for females
532
and males, respectively (Table 6) (Dallagnolo, 2008).
The largest males in the catches attained 62 mm and
the largest females 91 mm carapace length. Maturity
was reached, on average, in males and females with
carapaces of 46 mm and 29 mm long, respectively,
and reproduction was found to be continuous in the
fishing grounds throughout the year. Immature individuals have been rare in the catches (Anon, 2007).
Alistado shrimp, Aristeus antillensis A. Milne Edwards & Bouvier, 1909
The alistado shrimp was a minor component among
the aristeid shrimps exploited off Brazil, accounting
for approximately 5% of the total catches reported
between 2000 and 2007. The species was known to
occur in the western Atlantic as far south as French
Guiana, where it has been exploited along with the
scarlet shrimp (Guéguen, 2001). Chartered trawlers
reported this species in the northern sector of the Brazilian coast, but commercial concentrations have been
detected and exploited principally off central Brazil
(Pezzuto et al., 2006c; Dallagnolo et al., 2009).
Catches between 2005 and 2006 were considerably
lower than those reported for the other shrimps, peaking in 2005 at 15.8 ton (Table 5). A mean virginal
biomass of 49.8 ton was estimated for the fishing
grounds of the central sector in 2004. This biomass
was reduced by nearly half until 2007, particularly
after a maximum harvest rate of 32% exerted by chartered trawlers in 2005 (Dallagnolo, 2008). The latter
author also estimated an MSY for the species in 1922% of the exploitable biomass. The alistado is the
smallest of aristeid shrimps exploited off Brazil; samples measured on board have included males and females as large as 55 and 67 mm carapace length.
Catches have been greatly skewed towards large-sized
females (Anon, 2007).
Argentine short-fin squid, Illex argentinus (Castellanos, 1960)
Illex argentinus is an ommastrephid squid distributed
in the southwest Atlantic from the coast of Rio de
Janeiro State to southern Argentina. On the Patagonian shelf and around the Falkland/Malvinas Islands,
the species sustains one of the largest cephalopod
fisheries in the world (Haimovici et al., 1998). Off
Brazil, despite being regarded as a potential slopewater fishing resource since the 1970s (see review in
Haimovici et al., 2007), records of commercial
catches were scarce until the beginning of the chartered trawler operations in 2000 (Perez et al., 2003;
Perez et al., 2009a). In austral winter 2002, a South
Korean chartered trawler produced, in four complete
fishing trips off southern Brazil, a total of 1,400 ton,
the largest catches ever recorded in Brazilian waters.
These catches were concentrated in a relatively small
area off the “Santa Marta Grande” Cape between 26
and 29°S and the 250 and 500 m isobaths (Perez et al.,
2009a) and were followed by operations of national
trawlers. These trawlers contributed nearly 13% of the
total reported landings in 2002 (2,600 ton) (Perez &
Pezzuto, 2006). After that episode, annual landings
were greatly reduced and sustained basically by national trawlers at around 100-400 ton per year (Table
5). These catches were obtained off southern Brazil
below 250 m depth and have been highly seasonal,
concentrated in late winter-early spring (SeptemberOctober) (Perez & Pezzuto, 2006).
Trawl surveys conducted under the REVIZEE program estimated relative abundances much higher than
those obtained by previous surveys off southern Brazil
(Haimovici et al., 2006c, 2008). This pattern could be
attributed to abundance fluctuations, a natural characteristic of this annual species (Haimovici et al., 1998,
2006c). In addition, size and maturity data, as obtained
in both scientific and commercial catches, related
productive areas and fishing episodes to the austral
winter northward migrations of Patagonian stocks
spawning over the lower slope of southern Brazil
(Perez et al., 2009b). Other concentrations of smaller
mature males and females occur throughout the year
over the shelf break, but they have not been targeted
by the slope trawling fishery. Whereas the ecological
aspects involved in such migrations are not fully understood, it has been pointed out that any squid fishing
developed off Brazil would have to consider a shared
stock scenario with Argentina and Uruguay (Haimovici et al., 2006c). The species is currently considered within the upper slope trawl fishery management
plan as one of the target species (Table 7).
BYCATCH
The detailed recording of catch compositions by observers on board chartered vessels has provided opportunities to assess the impact of deep-water fishing on
the slope ecosystems of Brazil. The most comprehensive study to date has focused on a qualitative and
quantitative bycatch analysis of the chartered gillnet
fishery for monkfish during 2001 (Perez & Wahrlich,
2005). Absolute catches in numbers of non-targeted
species were estimated for the entire chartered gillnet
fleet in 2001 through their observed mean catch rates
(individuals per sampled net). These catches ranged
from (a) 33 to 459,833 for invertebrate species, most
notably the royal crab and spider crabs (family Majidae); (b) 41 to 23,954 in elasmobranchs, principally
533
the angel shark and various skates (family Rajidae);
(c) 41 to 110,665 in teleosts, namely the beardfish
(Polimixia lowei), silvery John dory, Brazilian codling, Argentine hake, wreckfish; and (d) 8 to 711 turtle, cetacean, and bird species. Indirect mortality impacts tended to be higher in mobile bottom dwellers
but bycatch abundances decreased and their basic
composition changed southwards, where large
teleosts, elasmobranchs, cetaceans, and birds were
dominant over the small teleosts, crustaceans, and
other invertebrates that characterized the bycatch
composition in the northern area. Non-intentional
mortality inflicted by bottom gillnets on large Kstrategists (wreckfish, sharks, rays, turtles, cetaceans,
birds) was regarded as critical, although highly correlated with operations in the southernmost areas of the
Brazilian EEZ, where these groups tend to concentrate.
Assessments of the latter and other slope fisheries
(including cephalopods and other invertebrates) have
been mostly qualitative (Perez et al., 2004, Bastos,
2004). A total of 185 macro and mega invertebrates as
well as sponges, cnidarians, annelids, crustaceans,
mollusks, and echinoderms were recorded in both
studies. Contrary to previous expectations, static gears
such as pots and gillnets were shown to catch a higher
number of sessile (~54%) than mobile species (~46%).
This pattern has been attributed to the intensive entangling of sessile fauna (mostly cnidarians) in these
gears during their retrieval, as the equipment is
dragged for a relatively long distance over the bottom
before being lifted from the seafloor. Considering the
length of the pot (9 km) and gillnet (20 km) lines used
during each fishing set, it has been argued that their
impact on benthic fauna may not be as unimportant as
previously thought. Closer attention has been paid the
impact of the trawling fishery directed at aristeid
shrimps on the lower slope because (a) this fishery
produces diverse bycatch of truly deep-water benthopelagic fishes (families Synaphobranchidae,
Macrouridae, Trachichthyidae, Berycidae, Astronestidae, Oreosomatidae, Ipnopidae, Alepocephalidae,
Ophidiidae, and others) (unpub. data) and (b) removes
deep-sea corals, particularly where they form slope
and seamount reef formations (Pires, 2007).
All the above assessments have been regarded as
empirical evidence necessitating the inclusion of ecosystem-based measures in deep-water fishery management plans, mostly through reduced efforts, bycatch restrictions, and marine protected areas (Table 7)
(Perez et al., 2002b, 2007b).
ECONOMICS
The chartering of foreign fishing vessels was a political instrument to develop deep-water fisheries off
Brazil and contribute to increased of foreign currency,
since most deep-water resources available in the Brazilian EEZ attained high prices in their main international markets. Soares (2007, 2008) analyzed the efficiency of this instrument by examining official records
of revenues obtained by deep-water products exported
between 2001 and 2006.
In this period, a total of US$ 8.3 million were negotiated from exports of 1,838.2 ton of frozen monkfish products, 78.39% of which was destined to EU
markets (mostly Spain) (Soares, 2008). As for deepsea crabs (Chaceon spp.), exports of 7,315.3 ton of
frozen products in the same period rendered US$ 12.4
million. From 2004 onwards, deep-sea crab exports
decreased as a direct consequence of the reduced effort by the chartered pot fleet (Soares, 2007).
Aristeid deep-sea shrimps have not been distinguished in Brazilian exports, which aggregate all
shrimp species exploited in the country. However,
considering the estimated prices of scarlet and giant
red shrimps in the European market (around US$ 20
per kg), the revenues accumulated between 2002 and
March 2006 can be estimated to have reached US$ 8.8
million (Soares, 2007).
Official figures such as those presented above,
however, have raised considerable uncertainties about
the economic importance of all deep-water fishing in
Brazil, particularly because prices of several species
negotiated by Brazil, as estimated from the total annual revenue – total annual catch ratio (i.e. monkfish
US$ 4.54 kg-1; deep-sea crabs US$ 1.70 kg-1), have
frequently remained significantly below known international prices (i.e. monkfish US$ 13.00 kg-1; deepsea crabs US$ 9.70 kg-1 1). The reasons behind such
inconsistencies are not clear, but they seem to be most
likely related to incorrect official records, either as a
result of inadequate product definitions in Brazilian
export customs or misreporting. In any case, a realistic
figure of total revenues obtained by the export of
deep-water resources is currently unavailable (Soares,
2007). According to chartering contracts signed by
both national and foreign partners, it is known, however, that only 5 to 10% of the total revenues obtained
by fish products generated by deep-water operations
were retained by Brazilian companies.
_____________________________
1
Average values obtained
www.bim.ie
in
several Spanish
markets
534
INSTITUTIONAL FRAMEWORK,
DEVELOPMENT, MANAGEMENT, AND
CONTROL
In the 1960s, Brazilian fishing activity changed radically as the so-called “industrial” fleet was structured
and unprecedented large-scale fishing regimes were
established on the continental shelf. Nearly forty years
later, deep-water fishing development passed another
turning point in the country’s fishing history, largely
provoked by the combination of increasingly uneconomic shelf resources and clear government incentives
to promote the occupation of the Brazilian EEZ. This
process involved new paradigms, not only of fishing
practices, areas, resources, and markets, as described
above, but also regarding the institutional framework,
development, management, and control.
Institutional framework
Until 1998, fishing management and control were
responsibilities of the Ministry of the Environment
(MMA), which was strongly rooted in an almost 40year-old coastal fishing-oriented management model.
Fishing administration was placed under this ministry
nearly 10 years before, as fishing resources were recognized in the Federal Constitution of 1988 as pertaining to the environmental resources, whose protection
and preservation were explicitly assured by the Law.
The Constitution was promulgated after the end of
more than two decades of dictatorial political regime
and strongly reflected the new democratic atmosphere
prevailing in the country. In fact, Article 225 stated
explicitly that not only the Public Power but also the
collectivity were both obligated to protect and preserve the environment for present and future generations. Such a political and institutional scenario
opened the opportunity for participatory management
practices to be attempted and reinforced in the following years (Marrul Filho, 2003). Mostly developed
through punctual and “open” multiparty meetings (i.e.
not organized under a formal structure in terms of
composition and functioning), forums promoted by the
MMA since the 1990s have focused mainly on overexploited coastal stocks demanding urgent management decisions.
In 1999, through political pressure from the fishing
industry interested in a more “development than environmentally-oriented philosophy”, a second management authority was created under the Ministry of Agriculture and Livestock (DPA/MAPA) with a mandate
to develop and manage aquaculture and the economic
exploitation of those stocks defined as “sub-exploited,
unexploited, and highly migratory”; overexploited
stocks remained under the jurisdiction of the MMA. In
essence, although no modifications of the national
fishing legal concepts were set up at that point, this
divided mandate allowed mostly oceanic and deepwater fishing policies to be promoted under a more
social and economic scope of development. Both legal
entities have co-existed ever since, not without strong
and continuous inter-institutional conflicts (Dias-Neto,
2003). Nonetheless, in 2003, DPA/MAPA was transformed into a Special Secretariat directly linked to the
Presidency of the Republic (SEAP/PR), and again, in
2009, into the Ministry of Fishery and Aquaculture
(MPA).
Development
Incentives for the development of the deep-water fishery in Brazil were materialized mostly in a short-term
chartering program launched by DPA/MAPA. This, in
essence, allowed national and overseas fishing companies to associate and operate foreign deep-water
vessels under temporary fishing authorizations. The
explicit objectives of the chartering program were: (i)
to enhance the fish supply in the domestic market and
to generate foreign currency; (ii) to improve competence and promote employment in the national fishing
industry; (iii) to occupy rationally and sustainably the
Brazilian EEZ; (iv) to stimulate the formation of a
national fleet capable of operating in deep-waters and
utilizing equipment that incorporates modern technology; (v) to expand and consolidate fishing enterprises;
(vi) to generate knowledge on living resources of the
continental shelf and EEZ; and (vii) to sustainably
exploit fishing resources on the high-seas. This government strategy led to the explosive development of
foreign fleets targeting new, valuable, fragile deepwater resources (Perez et al., 2002a, 2003, 2009a;
Pezzuto et al. 2006a, 2006c), in some cases, paralleled
by an expansion of coastal domestic fleets to the same
areas and resources (e.g. Perez & Pezzuto, 2006). Not
only did fishing efforts dramatically increase on virginal stocks for which the fishing potential was virtually unknown, but this process also stimulated conflicts between fleets and resulted in, within most of the
national fishing industry, a disregard for fishing authorities (namely DPA/ MAPA, SEAP/PR) and established management plans (see below).
Management
Concerns about the sustainability of the target species
as well as environmental, social, economic, and political impacts of such an uncontrolled scenario made
indispensable the development of an institutional
management framework that could provide investment
dimensions, access limits, and controls. At the end of
2002, the Consultant Committee for the Management
of Deep-water Resources (CPG) was created under the
MAPA and was maintained by SEAP/PR after 2003.
This committee inaugurated a new phase in the man-
agement of marine resources in Brazil, as participatory
practices finally crystallized in a formal and organized
multiparty forum. Delegates of the fishing sector (shipowners, fisherman, and fishing industry workers) and
governmental agencies compose the CPG, along with
an Executive Secretariat and members of Scientific
and Compliance Subcommittees (SCC and SC, respectively). Through annual ordinary meetings, the SCC2
produces the bulk of data and recommendations to be
discussed and approved at the regular CPG meetings.
Management plans and other recommendations from
the CPG have consultant power only, as the final decision is under the jurisdiction of the Secretariat.
Despite representing significant progress towards a
more rational management process in Brazil, the CPG
experience has not yet been totally successful. Fishing
development and its negative impacts have occurred
more rapidly than the bureaucracy (challenged by
political and institutional pressures) has been able to
deal with. Weak representativeness, the limited dependence of the users on deep-water resources, strong
intra- and intersectoral (government and industry)
disputes, incredulity regarding the enforcement of the
agreed measures, limited administrative structures
available to support the CPG activities, and general
inexperience with formal management forums are
some of the main problems that have limited the effective commitment of fishermen, the industry, and the
government to the sustainable development of deepwater fishing in Brazil.
Control
Managing deep-water fishing induced significant scientific, technological, and administrative advances.
Programs of fishery observers and satellite VMS were
developed for the first time in the country by 2001 in
response to greater demands for control measures and
data acquisition on deep-water fishing. Inserted within
pragmatic, government-induced, scientific research
programs that focused fully on deep-water-fishing,
such tools allowed large data sets and assessments to
be promptly generated, not only on fisheries and targeted stocks, but also on the deep-water environments
of Brazil as a whole. Today, both tools are incorporated into national policies for marine resource conservation, regardless of the exploration area and fishing resource, and with a potential for broadening current management practices.
The monkfish fishery: a case study
The deep-water monkfish fishery was the first to be
developed under the new institutional framework,
management process, and control practices. As such, it
is not only an example of their first practical imple-
535
mentation process but also illustrates the complexities
involved in attaining a sustainable use of this deepwater resource. Following the explosive start of the
fishery in the late 1990s, under the DPA/MAPA jurisdiction, biological, technological, and operational data
were collected intensively during 2001. A complete
stock assessment and management recommendations
were first made available to government and industry
in April 2002, even before reaching the CPG foundation (Perez et al., 2002b).
Scientific results and recommendations were subsequently analyzed and improved during the first two
SCC meetings of 2002. Three other meetings of a
special working group formed by the SCC, government, and industry members produced the first version
of the monkfish management plan. This plan was
approved under the CPG in December 2002 but was
not implemented until January 2003, when the recently elected President of the Republic created the
Special Secretariat for Aquaculture and Fishing
(SEAP/PR), which absorbed all responsibilities previously attributed to MAPA.
SEAP/PR then decided to reopen the debate on the
monkfish fishery in 2003, considering not only the
new institutional and political circumstances, but also
the strong opposition by the part of the industry interested in a more free-access regime to the fishery. A
new version of the management plan was discussed
and approved in November but, again, it was not implemented. After more than four years of uncontrolled
exploitation, in May 2004, the stock was declared to
be overexploited. As a consequence, the jurisdiction
on the species was shifted to the MMA, which also did
not implement the plan, in spite of the negative situation of the stock. Therefore, in March 2005, scientists,
members of the SCC, decided to adopt a strong political stance demanding legal intervention in the process
in order to ensure the sustainability of the stock and
respect for the Constitution. As a consequence, in May
of the same year, MMA and SEAP/PR implemented,
in cooperation, the monkfish management plan as
previously approved under the last CPG sessions (Table 7). Even after that, enforcement of management
rules has been poor and subsequent biomass assessments have not shown any signs of recovery.
The management of other deep-water resources
such as geryonid crabs, aristeid shrimps, and demersal
fishes has faced the same difficulties, with negative
consequences for the sustainability of the respective
stocks.
_____________________________
2
All authors of this review have been permanent members of
SCC CPG. The senior author has chaired the SCC since its
creation in 2002.
536
FUTURE PROSPECTS
The recent deep-water fishing development off Brazil
characterized what has been defined as a “gold-rush”
fishing episode, both revealing valuable fishing opportunities on the slope areas of the EEZ and accumulating conflicts and environmental losses. Future prospects are highly uncertain and dependent on solving
critical drawbacks that can be identified below as:
Developing a domestic deep-water fishing industry.
On the upper slope, the Argentine hake, Brazilian
codling, Argentine squid, and monkfish have been
quickly incorporated as targets of the national trawl
and gillnet fleet. Yet, on the lower slope, national
fishing for deep-water crabs and shrimps is currently
interrupted and may only be economically viable for
foreign vessels that can cope with the elevated costs,
lack of a domestic market, and uncertainties about
long-term economic sustainability. Unlike national
vessels, these originate from “distant-water” fleets and
are prepared to supply fishing products to the international market and to move to different fishing areas of
the world when opportunities for higher profits arise
through bi-lateral political arrangements. This picture
is not likely to change in the near future unless new
government incentives oriented at the formation of a
national truly deep-water fleet are made available to
the fishing industry. These incentives do exist in the
form of a vessel-financing plan (Program PROFROTA), but they have been highly unsuccessful
since they fail to neutralize the referred limitations and
risks associated with deep-water operations. Even if
such difficulties are overcome, it must be acknowledged that previous expectations of a large-scale slope
fishery now seem incompatible with the demonstrated
biological productivity. Sustainable and profitable
deep-water fishing off Brazil, if ever achievable, will
be restricted to a few highly controlled fishing units.
Promoting social and economic benefits. Whereas
environmental costs from the overexploitation of
deep-water resources have been quantified through
abundant and consistent data, benefits stemming from
the economic earnings have been obscure and underestimated due to the failure of the national export recording systems or deliberate misreporting of values
negotiated in the international market. It seems paradoxical that a public policy conceived to develop fishing would fail to promote an adequate dimensioning
of the benefits obtained by it. Unless this scenario is
reversed through strong actions from the fishing authorities, a more responsible political decision would
be to promote full conservation of the deep areas
within the Brazilian EEZ rather than the economic
exploitation of its fragile renewable resources.
Improving management practices. The CPG constituted an innovative institutional framework, setting a
direct path through which scientific assessments became subsidies to a participatory process of building
deep-water fisheries management plans. Such a
framework can be regarded as an important advance in
the country’s management practices and is thought to
promote (a) the required rupture with the obsolete
management model and (b) balanced exploitation of
valuable, fragile deep-water stocks. Both the fishing
industry and government, however, have so far failed
to explore the legitimacy of this forum and turn its
management proposals into effective actions. In combination with the institutional instability that has characterized the history of fishing management in Brazil
(see Paiva, 2004 for a review), these political difficulties have contributed to the overfishing of deep-water
resources. These resources may take a long time (if
ever) to recover to biologically safe levels. Hence, the
maintenance of the CPG as a promising management
mechanism may be at risk, as the expectations of the
industry for the effectiveness of this forum to promote
sustainable fishing earnings are frustrated in the long
run.
Amongst these critical issues, however, are advances in monitoring and control systems, positive
legacies that can radically contribute to public consciousness on the use of marine fishing resources in
Brazil. It is now expected that these legacies and the
lessons learned from this fishing episode may at least
play a role in the education of scientists, fishers, and
managers, allowing the definition of solutions that will
help the country recover the sustainable potential of its
valuable deep-water resources.
ACKNOWLEDGEMENTS
The Special Secretariat for Aquaculture and Fisheries
(SEAP/PR/027/2007) and National Council for Scientific and Technological Development (CNPq) research
grants to JAAP (Process 306184/2007-9) and PRP
(Process 310820/2006-5) funded this study.
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542
Lat. Am. J. Aquat. Res., 37(3): 543-554, 2009
Deepwater shrimp fishery in Pacific Costa Rica
543
Review
The deepwater fishery along the Pacific coast of Costa Rica, Central America
Ingo S. Wehrtmann1 & Vanessa Nielsen-Muñoz1
Unidad de Investigación Pesquera y Acuicultura (UNIP), Centro de Investigación en Ciencias del Mar y
Limnología (CIMAR), Ciudad de la Investigación, Universidad de Costa Rica, 2060 San José, Costa Rica
1
ABSTRACT. Global catches of marine fishery resources declined during the last decades; however, there has
been a trend of increasing exploitation of deepwater resources that are especially vulnerable to depletion. Such
a tendency was noticeable in Pacific Latin America, too. In Costa Rica, the vast majority of the commercial
fishing activities are concentrated on the Pacific coast. The target species for the deepwater fishery in Costa
Rica are the two pandalids Heterocarpus affinis and H. vicarius as well as Solenocera agassizii, the latter one
being the most important in terms of annual landings. Here we compile the information available from Costa
Rica about each of the three target species. Furthermore, we describe research activities related to the Costa
Rican deepwater resources and present available data about by-catch and discards in this fishery. Finally, the
current situation of the administration and management of these resources in Costa Rica is described.
Strengthening collaboration between governmental agencies, the fishery sector, non-governmental organizations, and the academic sector is recommended to avoid an uncontrolled overfishing of these valuable deepwater resources along the Pacific coast of Costa Rica.
Keywords: shrimp, Pandalidae, Solenoceridae, Heterocarpus, Solenocera agassizii, fishery management, bycatch, discard, Costa Rica.
Pesca en aguas profundas a lo largo de la costa Pacífica de Costa Rica,
América Central
RESUMEN. Las capturas globales de los recursos marinos pesqueros disminuyeron durante las últimas décadas. Sin embargo, se ha observado una tendencia de aumento en la explotación de los recursos de aguas profundas, los cuales son especialmente vulnerables a la extracción. Esta tendencia ha sido notable también en la
pesca a lo largo del Pacífico de Latino América. En Costa Rica, la mayoría de las actividades pesqueras comerciales se concentran en la costa del Pacífico. Las especies objetivo de la pesca de aguas profundas en Costa
Rica son los dos pandálidos Heterocarpus affinis y H. vicarius así como Solenocera agassizii, siendo esta última la más importante respecto a las capturas anuales. Se compila la información disponible sobre las tres especies objetivo de Costa Rica. Además, se describen las actividades de investigación relacionadas con los recursos de aguas profundas en Costa Rica y se presentan los datos disponibles sobre la fauna acompañante y el
descarte en esa pesquería. Finalmente, se describe la situación actual de la administración y manejo de dichos
recursos en Costa Rica. Se recomienda fortalecer la colaboración entre las agencias gubernamentales, el sector
pesquero, las organizaciones no-gubernamentales y el sector académico para evitar la sobre-explotación sin
control de estos valiosos recursos de aguas profundas del Pacífico de Costa Rica.
Palabras clave: camarones, Pandalidae, Solenoceridae, Heterocarpus, Solenocera agassizii, manejo pesquero,
fauna acompañante, descarte, Costa Rica.
________________________
Corresponding author: Ingo Wehrtmann: ([email protected])
544
GENERAL BACKGROUND
The Food and Agriculture Organization (FAO) of the
United Nations started compiling global fishery statistics in the 1950s. Their data indicated a rapid increase
in catches during the 1950s and 1960s; in the mid1980s a decline of the total catches became evident,
and this trend accelerated between the late-1980s and
early-1990s (Pauly et al., 2002, 2005; Zeller & Pauly,
2005). Global catches seemed to increase during the
1990s; however, the study by Watson & Pauly (2001)
revealed a systematic distortion in world fisheries
catch trends, mainly due to a substantial overreporting of catches from the People’s Republic of
China. The corrected data indicated, in fact, a declining trend since the late 1980s (Watson & Pauly, 2001;
Pauly et al., 2002; Schoijet, 2002). Moreover, this
trend was also masked by an increasing exploitation of
deepwater resources (Pauly et al., 2005).
In general, fishing activities have concentrated on
resources inhabiting shallow-water coastal areas. The
decline of these resources together with the increasing
demand and the development of new technologies
resulted in an expansion of fisheries in offshore areas
and deeper water (Pauly et al., 2005; Morato et al.,
2006). In fact, the mean depth of bottom fish catches
increased from around 103 m (early 1950s) to 145 m
in 2001 (Morato et al., 2006). According to these authors, the depth increase was especially pronounced
after 1978, with a rate of 13 m decade-1.
Deepwater species are considered to have a longer
life span, later sexual maturity, lower fecundity, and
slower growth; all these life history characteristics
make them especially vulnerable to depletion with a
low capacity for recovery from over-exploitation
(Cheung et al., 2005; Morato et al., 2006). A major
limitation for the development and implementation of
management measures is the lack of life history data
of the exploited deepwater species (Polidoro et al.,
2008).
The trend toward the exploitation of deepwater resources is also noticeable in Pacific Latin America.
The depletion of shallow water resources together
with fishing restrictions aimed at preserving the
threatened populations have fostered increasing interest, on the part of the fishing industry and scientists, in
identifying alternative resources in deepwater systems
(Arana et al., 2002; Wehrtmann & Echeverría-Sáenz,
2007). In recent years, several publications broadened
our knowledge about the diversity (e.g., Retamal,
1993; Guzmán & Quiroga, 2005; MacPherson &
Wehrtmann, in press), biology and ecology of deepwater decapods in Latin America (e.g., Campylonotus
semistriatus: Arana & Ahumada, 2006; Haliporoides
diomedeae: Arana et al., 2003; Neolithodes diomedeae
and Paralomis otsuae: Bahamonde & Leiva, 2003).
Moreover, Hendrickx (2003) published the results of
several studies concerning the deepwater decapod
fauna of the Golfo de California, Mexico. All these
studies focused on Chilean and Mexican waters, and
virtually nothing is known about deepwater resources
in Central America: Wehrtmann & Echeverría-Sáenz
(2007) described the crustacean fauna associated with
the fishery of the deepwater shrimp Heterocarpus
vicarius, and MacPherson & Wehrtmann (in press)
provided information on the occurrence of lithodid
crabs off Pacific Costa Rica.
FISHERY IN COSTA RICA
Although Costa Rica can be considered to be a relatively small country (land mass: 51,100 km2), its marine area, including Territorial Seas and Exclusive
Economic Zones (EEZ), is considerable and roughly
ten times larger than the land mass (589,683 km2:
INCOPESCA, 2006). This surprising fact can be attributed to the 200-mile zone in the Pacific, including
offshore Isla del Coco, that greatly enlarges the Exclusive Economic Zone of Costa Rica (Quesada-Alpízar,
2006a). Due to this situation, the marine territory of
Costa Rica shares borders with Ecuador and Colombia.
Starting around the 1990s, aquaculture began to
contribute to the total shrimp production of Costa
Rica. The importance of the aquaculture production
increased steadily, although the fishery landings during the late 1990s and early 2000s still comprised the
vast majority of the production of Costa Rica. This
situation changed in recent years (2004-2007): the
landing of the fishery sector decreased and, at the
same time, aquaculture production increased considerably. Nowadays, the contribution of the aquaculture
sector in Costa Rica is nearly of the same magnitude
as that of the fishery landings (Fig. 1).
The vast majority of commercial fishing activities
and landings are concentrated on the Pacific coast of
Costa Rica (Fig. 2), which covers approximately 1254
km versus only 212 km on the Caribbean coast (Cortés
& Wehrtmann, 2009). In the Pacific, the Golfo de
Nicoya is the most important fishery ground in the
country, accounting for roughly 30% of the annual
landings (Vargas, 1995; Cortés & Wehrtmann, 2009).
However, commercial bottom trawling is not allowed
in the inner part of the gulf and, thus, the small-scale
fishery is the prevailing type of fishing activity in the
Golfo de Nicoya.
545
Figure 1. Fishery and aquaculture production in Costa
Rica between the year 2000 and 2006 (data from FAO,
2009).
Figura 1. Producción en pesca y acuicultura en Costa
Rica durante los años 2000 y 2006 (datos: FAO, 2009).
The semi-industrial shrimp fishery in Costa Rica
originated in the 1950s with the introduction of bottom trawl nets; the first shrimp fishery statistics date
from 1952 and indicate landings of 43.2 tons (TabashBlanco, 2007, and references cited therein). In the
beginning, the principal target species of coastal
shrimp fisheries were Penaeus (Litopenaeus) occidentalis Streets, 1871 and Penaeus (Litopenaeus) vannamei Boone, 1931; other shrimp species were discarded (Tabash-Blanco, 2007). Currently, the following shrimp species are commercially exploited along
Pacific Costa Rica: Penaeus (Farfantepenaeus) californiensis Holmes, 1900 (“camarón café”), Penaeus
(Farfantepenaeus) brevirostris Kingsley, 1878
(“camarón pinki” or “camarón rosado”), Penaeus
(Litopenaeus) occidentalis (“camarón blanco del
Pacífico”), Penaeus (Litopenaeus) stylirostris Stimpson, 1874 (“camarón azul”), Penaeus (Litopenaeus)
vannamei (“camarón patiblanco”), Xiphopenaeus riveti Bouvier, 1907 (“camarón titi”), Solenocera agassizii Faxon, 1893 (“camarón fidel”), Heterocarpus
vicarius Faxon, 1893 (“camarón camello” or
“camarón camellito”), and H. affinis Faxon, 1893
(“camarón real” or “camarón camellón”). According
to INCOPESCA (A. Chacón, 2009, pers. com.), between 1995 and 2005, the annual shrimp landings
along the Pacific coast were distributed as follows: S.
agassizii 27.7%; P. occidentalis, P. stylirostris, and P.
vannamei 20.0%; H. vicarius 16.9%; P. brevirostris
15.0%; X. riveti 10.3%; and H. affinis 9.9%.
Shrimp trawling in Costa Rica is restricted to the
Pacific coast of the country, and the principal landing
dock for the shrimp trawling fleet is the city of Puntarenas, Golfo de Nicoya, central Pacific. The marine
fishery resources in Costa Rica are administrated by
Figure 2. Main fishing grounds of the deepwater fishery
(excluding Heterocarpus affinis) along the Pacific coast
of Costa Rica.
Figura 2. Principales áreas de pesca en aguas profundas
(excluyendo Heterocarpus affinis) a lo largo de la costa
del Pacífico de Costa Rica.
the “Instituto Costarricense de Pesca y Acuicultura”
(INCOPESCA), which was founded in 1994. According to this institution, the semi-industrial fishery fleet
consists of 72 registered fishing vessels; however,
only 52 of them are currently active and have valid
fishing licenses. A total of 45 vessels can operate in
coastal marine waters and seven in the deepwater
fishery (Bolaños, 2005). Trawlers fishing for shallow
water shrimp need to use a Turtle Excluder Device
(TED), whereas no such device is obligatory for
deepwater fishery in Costa Rica. A detailed description of the type of bottom trawl net used in the Costa
Rican semi-industrial shrimp fishery is provided by
Bolaños (2005). All vessels operate with two trawling
nets (Fig. 3), and most nets have a distance of 44.5
mm between knots (Bolaños, 2005).
EXPLOITED DEEPWATER SPECIES
Currently, there are three deepwater decapod species
that are of commercial interest in Costa Rica: the two
pandalid shrimps, Heterocarpus affinis and H. vicarius, and Solenocera agassizii (Decapoda:
Penaeoidea: Solenoceridae).
Heterocarpus affinis (Fig. 4)
Information regarding this species, locally known as
“camarón camellón” or “camarón real”, is extremely
546
Figure 3. A commercial shrimp trawler used for the deepwater fishery in Costa Rica. Photo: I.S. Wehrtmann.
Figura 3. Barco camaronero comercial utilizado en la pesca en aguas profundas en Costa Rica. Foto: I.S. Wehrtmann.
the data of H. affinis were pooled with those of H.
vicarius. Starting in 1995, their data were separated.
Landings of H. affinis increased steadily between
1995 and 1999; however, the highest annual landings
were recorded in 2003 with 225,277 kg (Fig. 6). Subsequently, landings decreased drastically and, since
2006, no more landings have been recorded. As far as
we know, H. affinis is not currently commercially
exploited in Costa Rica.
Figure 4. Lateral view of Heterocarpus affinis
(“camarón camellón”). Photo: I.S. Wehrtmann.
Figura 4. Vista lateral de Heterocarpus affinis
(“camarón camellón”). Foto: I.S. Wehrtmann.
scarce. Its known geographical distribution ranges
from the Golfo de California, Mexico, to approximately 8º43’S, Peru (Hendrickx & Wicksten, 1989).
The shrimp is known to occur between 760 and 1240
m depth (Hendrickx & Wicksten, 1989; Hendrickx,
2003). The species is considered to be a potential fishery resource in Peru (Hendrickx & Wicksten, 1989)
and can attain maximum sizes of 153 mm TL (total
length) (Hendrickx, 2003).
When considering the annual landings, despite its
large size, H. affinis is the least important deepwater
species in Costa Rica (Fig. 5). At the beginning of the
registration of annual shrimp landings in Costa Rica,
Figure 5. Costa Rica: percentages of shrimp landings for
each species or group of species (Penaeus spp.: P. occidentalis, P. stylirostris, and P. vannamei) during the
periods of 1995-2000 and 2001-2006 (data from
INCOPESCA).
Figura 5. Costa Rica: porcentajes de las capturas de
camarones por especie o grupo de especies (Penaeus
spp.: P. occidentalis, P. stylirostris y P. vannamei) durante los períodos de 1995-2000 y 2001-2006 (datos de
INCOPESCA).
Figure 6. Annual landings (1995-2006) of Heterocarpus
affinis (“camarón camellón”) from the Pacific of Costa
Rica (data from INCOPESCA).
Figura 6. Capturas anuales (1995-2006) de Heterocarpus affinis (“camarón camellón”) a lo largo del Pacífico
de Costa Rica (datos de INCOPESCA).
Heterocarpus vicarius (Fig. 7)
The geographic distribution of this species, locally
called “camarón camello” or “camarón camellito”,
ranges from the Golfo de California (Mexico) to Panama (Holthuis, 1980). The bathymetric distribution
covers the range from 73 to 550 m (Holthuis, 1980);
however, in Costa Rica, this species is commercially
fished mainly between 200 and 350 m depth, partly
co-occurring with the other deepwater species of commercial interest, S. agassizii. According to Holthuis
(1980), H. vicarius reaches a maximum size of 110
mm TL and 29 mm carapace length (CL). Data from
an ongoing monitoring program in Costa Rica revealed a sex proportion of 1:1 (n = 30,106); however,
in January, February, and March, females were dominant (I.S. Wehrtmann, unpubl. data). Ovigerous females can be found year-round; however, elevated
percentages of egg-bearing females (> 40%) generally
occur between June-July and September-October.
Information concerning the annual landings of H.
vicarius in Costa Rica has been collected since 1995;
previously, the data from H. affinis and H. vicarius
were put together, making it impossible to separate the
annual production of these two species. Considering
the period between 1995 and 2006 (Fig. 8), annual H.
vicarius landings were highest in 1996 and 1997 with
539,101 kg and 422,940 kg, respectively. Landings
dropped to a low in 1999 and then increased continuously until 2003, reaching 316,745 kg. After a new
drop in 2005, production increased in 2006 to 211,485
kg. Data from The Rainbow Jewels S.A., Puntarenas,
Costa Rica (R. Diers, unpubl. data) indicated a considerable decrease to less than 100,000 kg in 2007.
Currently, H. vicarius landings are negligible, and the
commercial deepwater fishery focuses on S. agassizii.
In fact, H. vicarius seems to have disappeared during
the last two years from the fishing grounds between
547
150 and 400 m depth. This alarming situation raises
the question as to whether this is the result of an overexploitation of the resource, if the species migrated to
other (deeper?) areas, or if other environmental factors
have caused or contributed to the almost complete
disappearance of H. vicarius in the fishing area reported in our study.
Figure 9 depicts the monthly landings of H. vicarius in 2004 (a “good” year) and 2007 (a “bad
year”). In 2004, the highest landings occurred between
February and August, representing 81% of the annual
landings. In February and March alone, 36% of the
yearly landings were obtained.
Solenocera agassizii (Fig. 10)
Three species of the genus Solenocera have been reported from the Pacific coast of Costa Rica
(Hendrickx, 1995; Vargas & Wehrtmann, 2009): S.
agassizii, S. mutator Burkenroad, 1938, and S. florea
Burkenroad, 1938. Locally known as “camarón fidel”,
S. agassizii is the most abundant and largest species of
the genus along the Pacific coast of the Americas.
According to Hendrickx (1995), males and females
can attain sizes up to 115 and 140 mm TL, respectively. However, females can reach even larger sizes
in Costa Rica (154 mm; I.S. Wehrtmann, unpubl.
data). The species is commercially exploited in Costa
Rica and Panama, and important quantities have also
been reported from the coast of Nicaragua (Holthuis,
1980; Hendrickx, 1995; Puentes et al., 2007). The
species can be found around the external portion of the
continental shelf down to 384 m and prefers soft bottoms (Hendrickx, 1995). In Costa Rica, the species is
fished mainly between 150 and 350 m depth (I.S.
Wehrtmann, unpubl. data).
In general, S. agassizii is the most important species in the commercial deepwater shrimp fishery in
Costa Rica. From 1995 to 2000 and 2001 to 2006, this
species comprised 27% and 29%, respectively, of all
reported shrimp landings (Fig. 5). When revising the
available historical data for this species, by far the
highest yearly landing was observed in 1986 with 2.6
x 106 kg. Subsequently, the landings dropped to values
well below 0.5 x 106 kg, with the exceptions of the
years 1994, 1995, and 2005 (Fig. 11). Preliminary data
for the years 2006 and 2007 indicate a considerable
reduction of S. agassizii landings to roughly 0.25 x 106
kg per year (I.S. Wehrtmann, unpubl. data). Figure 12
compares the monthly landings of S. agassizii in 2004
and 2007, a “good” and a “bad” year, respectively, for
the fishery of the species. In 2004, monthly landings
increased continuously from July to October, whereas
the lowest landings were observed in March and April.
548
Figure 7. Lateral view of Heterocarpus vicarius (“camarón camello”). Photo: I.S. Wehrtmann.
Figura 7. Vista lateral de Heterocarpus vicarius (“camarón camello”). Foto: I.S. Wehrtmann.
Figure 8. Annual landings (1995-2006) of Heterocarpus
vicarius (“camarón camello”) in the Pacific of Costa
Rica (data from INCOPESCA).
Figura 8. Capturas anuales (1995-2006) de Heterocarpus vicarius (“camarón camello”) a lo largo del Pacífico
de Costa Rica (datos de INCOPESCA).
The situation in 2007 did not reveal a clear pattern,
40% of the yearly landings were obtained in May,
July, and December.
RESEARCH ON DEEPWATER RESOURCES IN
COSTA RICA
Costa Rica does not have any research vessel, thus it is
not surprising that most marine research carried out so
far in this country concerns the flora and fauna of
shallow water habitats (Wehrtmann et al., 2009). Despite of its economic importance for Costa Rica, surprisingly little information is available concerning the
Figure 9. Monthly landings of Heterocarpus vicarius
(“camarón camello”) in 2004 and 2007 (data from The
Rainbow Jewels S.A., Puntarenas, Costa Rica)
Figura 9. Capturas mensuales de Heterocarpus vicarius
(“camarón camello”) en los años 2004 y 2007, con base
en datos facilitados por The Rainbow Jewels, S.A. (Puntarenas, Costa Rica).
different fishery and biological aspects of the shrimp
resources commercially exploited along the Pacific
coast. Most studies concerning decapods focus on
shallow water penaeid shrimp (Tabash & Palacios,
1996; Tabash-Blanco & Chávez, 2006; TabashBlanco, 2007) and the blue crab (Callinectes arcuatus
Ordway, 1863) (Fischer & Wolff, 2006). Additionally,
Campos (1983) reported on discarded by-catch of fish
and other organisms from the commercial shrimp
fishery in the Golfo de Nicoya and Golfo de Papa-
549
Figure 10. Lateral view of Solenocera agassizii (“camarón fidel”). Photo: I.S. Wehrtmann
Figura 10. Vista lateral de Solenocera agassizii (“camarón fidel”). Foto: I.S. Wehrtmann
Figure 11. Yearly landings (1986-2005) of Solenocera agassizii (“camarón fidel”) in the Pacific of Costa Rica (data from
INCOPESCA).
Figura 11. Capturas anuales (1986-2005) de Solenocera agassizii (“camarón fidel”) a lo largo del Pacífico de Costa Rica
(datos de INCOPESCA).
gayo, central and northern Pacific of Costa Rica, respectively.
Our knowledge on deepwater resources in Costa
Rica is even more limited. In fact, fishery-biological
studies of these resources started in the year 2004,
when the private fishery sector (Ristic AG, Germany,
and The Rainbow Jewels S.A., Costa Rica) together
with the Universidad de Costa Rica initiated a joint
effort to investigate the commercially exploited species H. vicarius and S. agassizii in order to facilitate
the development of a management plan for a sustainable fishery of these resources. This so-called “Public-
Private-Partnership” (PPP) project, financed mainly
through the German Federal Ministry for Economic
Cooperation and Development (BMZ) and the participating private companies, permitted scientists to have
regular access to samples taken between 150 and 400
m depth. More recently, a regional initiative between
Costa Rica, Nicaragua, and El Salvador aimed at
studying the deepwater resources and their sustainable
use along the Pacific of Central America was funded
and coordinated by the Consejo Superior Universitario
Centroamericano (CSUCA), the German Association
for Technical Cooperation (GTZ), and the University
550
Figure 12. Monthly landings of Solenocera agassizii
(“camarón fidel”) in 2004 and 2007, based on data provided by The Rainbow Jewels, S.A. (Puntarenas, Costa
Rica).
Figura 12. Capturas mensuales de Solenocera agassizii
(“camarón fidel”) en los años 2004 y 2007, con base en
datos facilitados por The Rainbow Jewels, S.A. (Puntarenas, Costa Rica).
of Kassel (Germany). This project forms part of the
Program University–Private Sector for Sustainable
Development (PUEDES). These collaborative efforts
between universities and the fishery sector have allowed the collection of valuable material, now deposited, e.g., in the Museo de Zoología of the Universidad
de Costa Rica. Moreover, many students have benefited from the access to trawling vessels and the collected samples that allowed them to develop their own
research projects and/or obtain important material for
their theses. One example of such collaboration is the
study on the diet composition of the threadfin anglerfish Lophiodes spilurus (Garman, 1899), one of the
most abundant fish associated with the deepwater
fishery in Costa Rican Pacific (Espinoza &
Wehrtmann, 2008). Their results revealed that L.
spilurus feeds exclusively on crustaceans (Decapoda
and Stomatopoda) and benthic teleost fish along the
Pacific of Costa Rica. However, our understanding of
the trophic dynamics of deepwater ecosystems is far
from complete.
BY-CATCH AND DISCARDS
Commercial bottom trawling is considered to be one
of the primary causes of physical perturbation to the
seabed on the continental shelf and upper slope (Watling & Norse 1998; Bozzano & Sardà, 2002). In general, these shrimp fishing gears are poorly selective;
they catch and retain large quantities of non-target
species, so-called “by-catch” (Andrew & Pepperell,
1992; Hall et al., 2000). Shrimp trawl fisheries, and
tropical shrimp fisheries in particular, have been iden-
tified as the single greatest source of discards, accounting for 27.3% of estimated total discards (Kelleher, 2005).
In Costa Rica, practically the entire by-catch of the
deepwater fishery is discarded. Even species which
are of commercial value in other Central American
countries ((e.g., the squat lobster Pleuroncodes
planipes (Stimpson, 1860)) are thrown away.
The crustacean fauna associated with the deepwater fishery of H. vicarius in the Pacific of Costa Rica
was studied by Wehrtmann & Echeverría-Sáenz
(2007). They encountered 28 decapods and two
stomatopod species. Apart from the co-occurring target species S. agassizii, the most common by-catch
species were Squilla biformis Bigelow, 1891 (Squillidae), Plesionika trispinus Squires & Barragan, 1976
(Pandalidae), and Pleuroncodes sp. (Galatheidae),
reaching maximum total catch percentages of 81.5%,
91.8%, and 99.6% of individual catches, respectively.
Crustaceans were predominant in all three depth
ranges (200-249 m, 250-300 m, 301-350 m), and the
percentage of fish as part of the total catch decreased
continuously and inversely with depth from 16% (200240 m) to 8% (301-350 m).
Figure 13 depicts the by-catch composition associated with the deepwater shrimp fishery along the Pacific coast of Costa Rica from 2004 to 2008. The most
striking result is the continuous decrease and almost
complete disappearance of one of the target species,
H. vicarius; at the same time, the portion of stomatopods increased steadily, reaching more than 53% in
2008. Interestingly, the increase of stomatopods was
not restricted to the Costa Rican fisheries, but was also
observed in the Pleuroncodes fishery in El Salvador
(F. Chicas & N. Hernández, unpubl. data). More studies are needed to document and to understand the
processes related to the observed changes in the species composition of the deepwater fauna along the
Pacific coast of Central America. Moreover, the
steady increase of stomatopods as part of the by-catch
fauna as well as the apparent disappearance of H.
vicarius require further attention (Fig. 13).
FISHERY MANAGEMENT
The management of Costa Rican marine fishery resources is the responsibility of the “Instituto Costarricense de Pesca y Acuicultura” (INCOPESCA). This
institution has the legal authority to regulate both (1)
the sustainable use of hydrobiological resources and
(2) the protection of related ecosystems. However, the
Ministry of Environment, Energy, and Telecommunications (MINAET) is responsible for the design and
establishment of protected areas and has jurisdiction
551
Figure 13. Catch composition of the deepwater fishery in Costa Rica from 2004 to 2008, indicating the average fishing
depth per year.
Figura 13. Composición de las capturas de la pesca de aguas profundas en Costa Rica durante los años 2004-2008, indicando la profundidad promedio de pesca por año.
over the marine resources within marine protected
areas. Finally, the National Coast Guard is responsible
for the protection of the marine resources and the enforcement of fishery management related regulations
in the EEZ of Costa Rica. According to QuesadaAlpízar (2006b), the lack of an efficient legislation has
limited INCOPESCA’s management capabilities,
which, in turn, has led to increased deterioration of
marine resources.
As far as we know, no management plan has been
implemented by INCOPESCA for the use of the
deepwater resources in Costa Rica. In fact, due to the
numerous limitations confronting INCOPESCA (e.g.,
lack of adequate infrastructure and human resources),
information concerning biological-fishery aspects of
these resources has been generated so far exclusively
by the Universidad de Costa Rica in close collaboration with the private sector (Wehrtmann & EcheverríaSáenz, 2007). The statistics of the annual landings of
deepwater shrimp are based upon the data provided by
the fishery sector; since INCOPESCA does not have
the manpower to verify these data, the fishery statistics presented by this institution may not necessarily
reflect the real production of the different commercially exploited species.
CONCLUSIONS AND RECOMMENDATIONS
The situation of all three commercially exploited
deepwater species (H. affinis, H. vicarius, and S. agassizii) in Costa Rica is alarming. Currently, the com-
mercial fishery for the two pandalid shrimp, H. affinis
and H. vicarius, has stopped. This has not been the
result of an adequate and consequent management
plan, but is related to the near disappearance of these
resources within the current fishing grounds that
forced the fishery sector to move on to other resources
or to abandon the fishery, provoking important social
and economical consequences. Together with their
partners from the fishery sector and based on the data
generated by this collaboration, during recent years,
the Universidad de Costa Rica officially informed
INCOPESCA twice about the alarming situation of the
deepwater fishery and suggested a temporary closure
of the fishery of selected species. Unfortunately, these
suggestions have not been implemented by the national fishery authority.
We see an urgent need to join forces between the
private fishery sector, the governmental institutions
(INCOPESCA, MINAET), non-governmental organizations interested in the sustainability of the marine
ecosystem, and the academic sector. Such a joint effort is necessary because the special life history characteristics of these deepwater species make them vulnerable to depletion and they have only a limited capacity to recover from over-exploitation (Cheung et
al., 2005; Morato et al., 2006). Therefore, solid information about the life history parameters of the exploited species is needed. Such basic information is
essential for the development and the implementation
of any management measure (Polidoro et al., 2008).
The recent foundation of the Unidad de Investigación
Pesquera y Acuicultura (UNIP) at the Universidad de
552
Costa Rica (UCR), co-financed by the UCR and the
fishery sector (The Rainbow Export Processing, S.A.,
Puntarenas), is certainly a promising step in the correct direction. Moreover, the UNIP will play a key
role in the formation of much needed qualified personal to carry out the scientific analyses and to support
the development and monitoring of adequate management programs.
It is recommended that all relevant stakeholders establish, as a joint effort, a monitoring program of the
deepwater resources and associated by-catch. Moreover, the use of more selective fishing methods should
be encouraged in order to reduce the amount of discarded biomass as well as to study possibilities for an
adequate (commercial) use of the discards. At the
same time, the establishment of temporary and spatial
fishery regulations should be considered to protect the
threatened deepwater resources of Costa Rica.
The Costa Rican fishery authorities are encouraged
to revise the legal framework of the legislation and
fishery management of the deepwater shrimp Heterocarpus reedi Bahamonde, 1955 in Chile, a species
with a similar ecology to H. vicarius (Roa & Ernst,
1996). The Chilean management strategy includes
public auctions of fishery quotas, accompanied by a
scientific research program that acts as a basis for
establishing future fishery quotas for the target species. The lack of efficient control mechanisms limits
the implementation of any management plan in Costa
Rica. However, the national fishery authorities have
the responsibility to protect the marine resources and
need to put into practice adequate measures to avoid
uncontrolled overfishing of these valuable deepwater
resources along the Pacific coast of Costa Rica.
ACKNOWLEDGMENTS
The study of the deepwater fishery in Costa Rica
would not have been possible without the excellent
collaboration of The Rainbow Jewels, S.A., Puntarenas, which allowed us to collect samples with their
commercial shrimp trawlers. We would like to thank
Ronny Gründler and René Diers, the previous and
current general manager of the company, respectively,
for their tremendous support during all these years. A
special thanks goes to the crews of the commercial
shrimp trawlers of this company, especially to the
captain of the boat “Onuva”, Rigoberto Villalobos
Cruz. Much of the research formed part of a so-called
Public-Private Partnership project about the development of standards for sustainable deepwater shrimp
fisheries in Pacific Costa, financed by the German
Federal Ministry of Economic Cooperation and Development (BMZ), the company Ristic AG (Oberfer-
rieden, Germany), and the Universidad de Costa Rica
(project V.I. No. 111-A4-508). Adam Chacón
(INCOPESCA) facilitated unpublished shrimp fishery
data, which is greatly appreciated. Catalina Benavides
(UNIP) helped us with the preparation of Figure 2.
Finally, we are most grateful to the students and assistants (Silvia Echeverría, Fresia Villalobos, Jaime
Nivia, Patricio Hernáez, Jeffry Ortiz, Tayler Clarke,
Juliana Herrera, Edgar Villegas, just to mention some)
who helped during the years with the collection and
processing of the deepwater samples. To all of them:
¡Muchas gracias! Finally, we appreciated the constructive comments of the referees.
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Lat. Am. J. Aquat. Res., 37(3): 555-570, 2009
Seamounts and biodiversity in Chile
555
Review
Seamounts in the southeastern Pacific Ocean and biodiversity on
Juan Fernandez seamounts, Chile
Eleuterio Yáñez1, Claudio Silva1, Rodrigo Vega2, Fernando Espíndola3, Lorena Álvarez1, Nelson Silva1,
Sergio Palma1, Sergio Salinas1, Eduardo Menschel2, Verena Häussermann4,
Daniela Soto1 & Nadín Ramírez1
1
Pontificia Universidad Católica de Valparaíso, P.O. Box 1020, Valparaíso, Chile
2
Universidad Austral de Chile, P.O. Box 567, Valdivia, Chile
3
Instituto de Fomento Pesquero, P.O. Box 8-V, Valparaíso, Chile
4
Fundación Huinay, P.O. Box 462, Puerto Montt, Chile
ABSTRACT. Seamounts are vulnerable marine ecosystems. In Chile, information on these ecosystems is
quite scarce; thus, a compilation of information on their geographical distribution and biodiversity is presented
herein. A total of 118 seamounts distributed in the Chilean EEZ are identified and characterized. Additionally,
an in situ assessment was carried out on the Juan Fernandez seamounts 1 and 2 (JF1 and JF2), which were also
oceanographically characterized. Phytoplankton, zooplankton, and marine invertebrate samples were collected
and an exploratory fishing survey was executed using different gears. According to the bibliographical review,
a total of 82 species have been collected on the JF1 and JF2 seamounts, highlighting findings of black coral
species caught in lobster traps at the Juan Fernandez Archipelago. Submarine images of the marine substrate at
JF1 and JF2 reveal characteristics attributable to the impact of bottom dredges, coinciding with the information obtained from the trawling fleet. The fishing activity was carried out primarily at JF2 (4,667 km of trawling). The monthly fishing effort increased considerably in 2002, 2003, and 2005, reaching values above 500
km of trawling and, thus, modifying the spatial structure of the resource aggregates on the JF2 seamount.
Keywords: seamounts, identification, biodiversity, fishing impact, Juan Fernández Archipelago, southeastern
Pacific.
Montes submarinos en el océano Pacífico suroriental y biodiversidad en el cordón
de Juan Fernández, Chile
RESUMEN. Los montes submarinos constituyen ecosistemas marinos vulnerables. Chile presenta una escasa
información acerca de estos ecosistemas, por lo que este trabajo recopila información sobre distribución geográfica y biodiversidad. Se identifican y caracterizan 118 montes en la ZEE de Chile. Adicionalmente, una
evaluación in situ se desarrolló sobre los montes Juan Fernández 1 y 2 (JF1, JF2), caracterizándolos oceanográficamente. Se recolectaron muestras de fitoplancton, zooplancton e invertebrados marinos, y se realizó pesca exploratoria con diversos artes. La revisión bibliográfica establece que en JF1 y JF2, se han capturado un
total de 82 especies, destacándose la presencia de corales negros en trampas langosteras en el archipiélago de
Juan Fernández. Fotografías submarinas de los montes JF1 y JF2 presentan características atribuibles al impacto de artes de arrastre de fondo, concordante con información de la flota. El esfuerzo de pesca se realizó
mayormente en JF2 (4.667 km arrastrados). El esfuerzo de pesca mensual se incrementó considerablemente
durante el 2002, 2003 y 2005, alcanzando valores sobre 500 km arrastrados, modificando la estructura espacial
de las agregaciones de recursos en el monte JF2.
Palabras clave: montes submarinos, identificación, biodiversidad, impacto pesquero, archipiélago de Juan
Fernández, Pacífico suroriental.
556
INTRODUCTION
The marine environment is currently under serious
depletion as a result of overfishing, contamination,
and the direct and indirect impacts of climate changes.
The anthropogenic and climate impacts observed in
many places have caused dramatic changes in ecosystems. This is the case of seamounts, vulnerable marine
ecosystems in which a decrease of biostructureforming species and a collapse of oceanic fisheries
have been observed. The vulnerability of these ecosystems is related to the possibility that a population,
community, or habitat will experience a substantial
alteration, which may be irreversible or of slow restoration (FAO, 2007). The international information on
seamount biodiversity and ecology is limited, especially for those at depths exceeding 300 m (Tracey et
al., 2004). Therefore, although thousands of seamounts are estimated to exist around the world, only
around 200 have been biologically sampled, in most
cases, during commercial fishing activities (Probert et
al., 1997; Gálvez et al., 2006).
In Chile, there is lack of information for an undetermined number of seamounts in the Economic Exclusive Zone (EEZ). Research on seamount biodiversity along the Chilean coast has been carried out since
1950, mainly by the Russian government on the Nazca
and Salas and Gomez ridges, beyond the EEZs of
Chile and Peru (Parin et al., 1997). The information
on the Juan Fernandez Archipelago (33ºS-78ºW) is
limited to the H.M.S. Challenger scientific expedition
(1873-1876), the Pacific Swedish expedition (19161917), and the B/I Anton Bruun expedition (1966)
(Rozbaczylo & Castilla, 1987), as well as the oceanographic cruises MARCHILE VIII and IX of 1972 and
1973, respectively (Cerda, 1977), the CIMAR 5 and 6
Oceanic Islands cruises in 1999 and 2000 (Rojas et al.,
2004), and the scientific survey of B/I Koyo Maru in
2004 (Zuleta & Hamano, 2004). Furthermore, information has been systematically collected on fauna
associated with bottom dredges over Chilean seamounts (Gálvez et al., 2006).
The objective of this work, considering the international demand for information on vulnerable marine
ecosystems such as seamounts (Resolution 59/25 of
the ONU General Assembly), is to determine the geographical distribution of seamounts in the Chilean
EEZ, including a biodiversity and fishing impact study
on some seamounts of the Juan Fernandez Archipelago.
generated using 2’ x 2’ resolution satellite altimetry
data (Smith & Sandwell, 1997) and 1’ x 1’ resolution
sounding data (GEBCO, 2003), according to the
Kitchingman & Lai methodology (2004). Furthermore, in situ assessments were carried out on two
seamounts of the Juan Fernandez Archipelago – Juan
Fernandez 1 (JF1) and Juan Fernandez 2 (JF2) –
through two exploratory campaigns at 247 and 292 m
depth, the respective depths of their tops. The first was
executed aboard the PAM Portugal II in July-August
2007, and the second was carried out aboard two artisanal boats in November-December 2007: Boat No.
58 Cumberland and L/M Alborada. All the relatively
flat area accessible for fishing and sampling systems
(over 700 m deep) was systematically gridded (0.5 x
0.5 tenths of degrees), and a grid was randomly selected for sampling.
Three different depth strata were analyzed: pelagic,
demersal, and benthic. Different fishing systems were
also used: vertical longlines (1,264 hooks), handlines
(12 hooks), fishing pots (108 traps), surface longlines
(440 hooks), zooplankton nets (10 haul), dredging (5
haul), submarine camera observations (4 observation
periods), and oceanographic surveys of the water column (CTD and Niskin Bottles). The surface oceanographic characteristics were analyzed using satellite
information (NOAA, TOPEX, SeaWins, SeaWifs).
Additionally, a bibliographical analysis was done
to determine the different species previously collected
during surveys, cruises, and commercial fishing activities carried out on these seamounts. Finally, an evaluation of the fishing effects index (FEI) (O’Driscoll &
Clark, 2005) was done in the same area of study. This
index involves data on the fishing effort executed on
each seamount, the direction of the trawling, and the
seamount area. On one hand, this index measures the
fishing density on a seamount as a proportion of its
area; on the other hand, it reflects a scale factor that is
proportional to the directions the seamount was
trawled. A high FEI value may be explained through a
heavy effort relative to the seamount size and the fact
it was trawled in all directions. The information used
for this analysis corresponds to data from fishing binnacles of the industrial trawling fleet operating over
orange roughy (Hoplostethus atlanticus) and alfonsino
(Beryx splendens) between 2000 and 2006. The same
data was used to analyze the spatial structure dynamics of the resources in 2001 and 2003 through geostatistical techniques.
RESULTS
The geographical seamount identification and distribution was determined through the analysis of images
A total of 118 seamounts were identified in seven
areas of the Chilean EEZ (Fig. 1): 35 around Easter
Island (25º-30°S, 105º-112°W) (Fig. 2), 21 near San
Figure 1. Areas where seamounts were identified in the
southeastern Pacific Ocean. NZ: northern zone, EI: eastern island, SF: San Félix island, ZC: central zone, JF:
Juan Fernández Archipelago, SZ: southern zone, SAZ:
far-southern zone.
Figura 1. Localización de áreas donde se identificaron
montes submarinos en el océano Pacífico suroriental.
NZ: zona norte, EI: isla de Pascua, SF: isla San Félix,
ZC: zona central, JF: archipiélago de Juan Fernández,
SZ: zona sur, SAZ: zona sur austral.
Felix Island (24°-29°S, 76°-84°W) (Fig. 3), 21 off
northern Chile (18°-30°S, 71°-75°W) (Fig. 4), 15
around the Juan Fernandez Archipelago (30°-35°S,
76°-82°W) (Fig. 5), eight in the central area of the
country (30°-40°S, 71°-76°W) (Fig. 6), nine in the
southern area (40°-50°S, 73°-79°W) (Fig. 7), and 10
off far-southern Chile (50°-58°S, 70°-77°W) (Fig. 8).
This identification included the geographical location,
surface area, and depth of these seamount tops and the
designation of codified names (see Yañez et al. 2008
for details).
Seamounts JF1 and JF2 have volcanic substrate,
which is mainly constituted by bare rock and sand.
These seamounts are influenced by several water
masses: Subtropical Water (STW), Subantarctic Water
(SAAW), Equatorial Subsurface Water (ESSW), and
Antarctic Intermediate Water (AAIW), but are predominantly influenced by SAAW and STW (Fig. 9).
The vertical distribution of dissolved oxygen showed a
two-layer structure. The well-oxygenated surface
structure of approximately 100 m with concen-
557
Figure 2. Locations and codes assigned the seamounts
identified in the Easter Island area (EI).
Figura 2. Localización y código asignado a los montes
submarinos identificados en la zona de Isla de Pascua
(EI).
identified in the area of San Felix Island (SF).
submarinos identificados en la zona de isla San Félix
(SF).
558
identified in the area of the Juan Fernandez Archipelago
(JF).
submarinos identificados en el cordón de Juan Fernández
(JF).
identified in the northern zone (NZ) (18°-30°S).
submarinos identificados en la zona norte (NZ) (18°30°S).
trations greater than 5 mL L-1 (90-100% saturation) is
the result of oxygen-atmosphere exchange and primary production in the area. Beneath this layer and at
approximately 200 to 300 m depth, the dissolved oxygen was quickly reduced to concentrations of less than
1 mL L-1 (5-20% saturation); the latter drop was
caused by the presence of ESSW coming from off
Peru (Fig. 10). A slight current system was observed
in July-August (winter) with sea surface temperature
(SST) anomalies that were negative at JF1 and positive at JF2. The SST showed a typical cold condition
of 10° to 17°C, surface salinity of approximately 34.3,
and chlorophyll concentrations between 0.09 and 1 mg
m-3. In November-December (spring), however, a
greater amount of mesoscale structures such as shifts
identified in the central zone (CZ) (30°-40°S).
submarinos identificados en la zona central (CZ) (30°40°S).
559
identified in the far-southern zone (SAZ) (50°-58°S).
submarinos identificados en la zona sur-austral (SAZ)
(50°-58°S).
identified in the southern zone (SZ) (40°-50°S).
submarinos identificados en la zona sur (SZ) (40°-50°S).
Figure 9. T-S diagram of the oceanographic stations for the seamounts a) JF1 and b) JF2.
Figura 9. Diagrama T-S de estaciones oceanográficas para los montes a) JF1 y b) JF2.
560
Figure 10. Vertical distribution of dissolved oxygen at eight oceanographic stations.
Figura 10. Distribución vertical de oxígeno disuelto en ocho estaciones oceanográficas.
and currents were observed. The STW showed a cold
condition that is typical of the season, with SST of 13
to 18°C; surface salinity close to 34.1, and a chlorophyll-a concentration around 4 mg m-3.
The phytoplankton collected on the surveyed seamounts involved seven classes of organisms that were
classified into 31 genera, 23 species, and other nonidentified species. Fifty percent of the organisms were
classified as “other flagellates”, another 40% corresponded to the Dinophyceae class, and the remaining
7% included the Bacillariophyceae (3.3%), Ciliata
(2.1%), Cianophyceae (1.4%), Dictyochophyceae
(0.15%), Chlorophyceae (0.04%), and Acantharia
(0.01%) (Table 1). Meanwhile, a total of 52,309 organisms were identified as zooplankton; these were
distributed among 16 taxonomic groups belonging to
the phyla Cnidaria, Ctenophora, Chaetognatha, Annelida, Nemertina, Arthropoda, Tunicata, and Vertebrata. An 87.8% of the organisms were chitinous
(euphausiids, mysids, amphipods, ostracods, copepods, cirripedia, decapod crustacean larvae), 11.6%
were gelatinous and semi-gelatinous (jellyfish, siphonophores, ctenophores, chaetognaths, salps, appendicularians, polychaetes, nemertins) and the remaining 0.6% corresponded to ichthyoplankton (Hygophum brunni, Sardinops sagax) (Table 2).
The fishing methods allowed catches of two pelagic species, blue shark (Prionace glauca) and snoek
(Thyrsites atun); two demersal species, croaker (Helicolenus lengerichi) and depth conger (Pseudoxenomystax nielseni); and two crustacean species, golden
crab (Chaceon chilensis) and Juan Fernandez king
crab (Paromola rathbuni). A total of 409 invertebrates
were collected using a dredge. These represented important groups of species such as Echinoidea (Echinacea), Polychaeta, Porifera, Actinaria, and Asteroidea
(Table 3). Due to the complexity of the identification,
only two taxa have been identified to this date: 1)
Asteroidea new species of Smilasterias and 2) Gorgonia species Callogorgia kinoshitae (Kükenthal, 1913).
Only preliminary results are available for other species.
The bibliographical review established that, during
the 2001 to 2006 fishing activities, a total of 82 species were collected from the JF1 and JF2 seamounts;
these belonged to four phyla (Chordata, Arthropoda,
Mollusca, Echinodermata) and the families Macrouridae (9), Moridae (6), and Dalatiidae (4) stood out. The
presence of black coral species (Parantipahes fernandenzii, Trisopathes spp., Leiopathes spp.) in lobster
traps used around the Juan Fernandez Archipelago
deserve mention (Arana et al., 2006).
561
Table 1. Composition and abundance of nano-microplankton (cel L-1) on the seamounts Juan Fernández 1 and Juan Fernández 2. Only the mean of each taxonomic group is
indicated.
Tabla 1. Composición y abundancia de nano-microplancton (cel L-1) en los montes submarinos Juan Fernández 1 y Juan Fernández 2. Se indica el promedio de cada grupo.
Station
Species
Acantharia
Nasselaria
Bacillariophyceae
Bacteriastrum sp.
Chaetoceros atlanticus
Chaetoceros peruvianus
Chaetoceros spp.
Cylindrotheca closterium
Dactyliosolen sp.
Nitszchia longissima
Nitszchia spp.
Pennadas indeterminates
Pleurosigma spp.
Pseudonitzschia spp.
Rhizosolenia alata
Rhizosolenia bergonii
Rhizosolenia spp.
Thalassiothrix sp.
Cianophyceae
Ciliata
Acanthostomella norvegica ?
Ascampbeliella sp.
Ciliates (> 15 μm)
Ciliates (< 15 μm)
Dictiocysta elegans
Dictiocysta mitra
Dictiocysta sp.
Eutintinnus fraknoi
Eutintinnus lusus-undae
Depth (m)
1
0
0
0
60
0
0
0
0
0
20
0
0
20
0
0
0
0
20
0
0
140
0
0
40
0
0
0
40
0
20
2
50
20
20
140
0
0
0
0
0
0
0
0
80
0
60
0
0
0
0
0
160
0
0
60
0
20
0
0
20
20
0
50
0
0
0
0
1040 180
0
0
0
0
0
0
0
0
40
0
0
0
40
0
0
0
80
40
0
0
840 140
0
0
40
0
0
0
0
0
480 1820
600 160
0
0
0
0
200 140
0
0
40
20
0
0
80
0
0
0
200
0
3
0
0
0
880
80
0
0
0
0
0
40
0
180
0
500
20
40
0
20
0
540
0
0
320
0
0
0
20
40
80
4
50
0
0
960
0
0
0
0
0
80
0
0
80
0
760
0
0
40
0
0
200
0
0
0
0
0
0
0
0
160
0
0
0
320
0
0
0
0
0
0
0
0
80
0
200
0
0
0
40
780
320
0
20
160
0
0
40
0
0
40
5
50
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
s/i
0
0
0
620
0
120
0
40
20
20
0
0
40
0
140
0
20
220
0
0
1837
0
0
740
920
0
40
0
0
20
6
50
0
0
540
0
0
0
0
20
0
0
0
320
0
0
0
0
200
0
0
3299
0
0
440
2759
0
40
0
0
40
0
0
0
20
0
0
0
0
0
0
0
0
20
0
0
0
0
0
0
0
560
0
0
500
0
0
0
0
0
0
7
50
0
0
160
0
0
0
0
0
0
0
0
40
0
40
0
0
80
0
0
80
0
0
80
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
300
0
0
280
0
0
0
0
0
0
8
50
0
0
240
0
0
0
0
0
20
0
0
20
0
160
0
0
40
0
0
420
0
0
340
0
0
60
0
0
20
0
0
0
2720
320
0
40
160
320
280
0
0
320
0
1040
0
0
240
0
0
240
0
0
120
0
0
0
0
0
0
Mean
50
80
80
1760
0
0
0
40
160
200
0
0
160
0
1200
0
0
0
0
0
960
0
0
600
0
0
0
40
0
40
7
643
205
654
562
Laboea spp.
Parundela caudata
Protorhabdonella curta
Rhabdonella chilensis
Rhabdonella sp.
Salpinguella sp.
Steentrupiella pozzi
Undella sp.
Undella claparedei
Xystonella treforti
Dictyochophyceae
Dictyocha fibula
Dictyocha sp.
Dictyocha speculum
Dinophyceae
Ceratium extensum
Ceratium furca
Ceratium fusus
Ceratium tripos
Athecate dinoflagellates (> 15 μm)
Athecate dinoflagellates (< 15 μm)
Thecate dinoflagellates
Dinophysis sp.
Dissodinium sp.
Gonyaulax polygramma
Ornithocercus sp.
Oxytosum sp.1
Oxytosum sp.2
Podolampas sp.
Prorocentrum sp.
Protoperidinium conicum
Protoperidinium sp.
Scripsiella sp.
Flagellata
Flagellates/Ciliates (< 10 μm)
Flagellates (< 10 μm)
0
0
0
20
20
0
0
0
0
0
20
20
0
0
2039
0
40
40
0
100
1839
0
0
0
0
0
20
0
0
0
0
0
0
2759
0
2759
0
20
0
0
0
20
0
0
0
0
0
0
0
0
5038
0
40
40
0
280
4598
0
0
0
20
0
60
0
0
0
0
0
0
2759
0
2759
0
0
0
40
0
0
40
0
0
0
40
0
40
0
8677
0
0
80
0
200
8277
0
0
40
0
0
40
40
0
0
0
0
0
2759
0
2759
0
0
0
0
0
0
0
0
0
0
20
0
20
0
8937
0
40
20
0
380
8277
20
0
0
0
0
100
60
40
0
0
0
0
4139
0
4139
40
0
0
0
0
40
0
0
0
0
40
40
0
0
7897
0
40
80
0
320
7357
0
0
0
0
0
80
20
0
0
0
0
0
5058
0
5058
s/i
0
20
0
s/i
0
0
40
s/i
0
0
0
s/i
0
40
0
s/i
0
0
0
s/i
40
0
0
s/i
0
0
20
s/i
0
0
0
s/i
0
0
20
s/i
0
0
0
0
0
20
s/i
0
0
0
s/i
0
0
0
s/i
0
0
20
3959 10417 - 11456
s/i
0
0
0
s/i
40
0
20
80
120 s/i
40
s/i
0
0
20
40
460 s/i 240
3679 9657 s/i 11036
s/i
0
0
20
s/i
0
0
20
s/i
0
0
0
s/i
0
0
20
s/i
0
0
0
s/i
0
20
20
120
160 s/i
0
s/i
0
0
0
s/i
0
0
0
s/i
0
0
20
s/i
0
0
0
s/i
0
0
0
4598 13795
22072
s/i
0
0
0
4598 13795 s/i 22072
0
0
0
0
0
0
20
0
0
0
20
20
0
0
16336
20
40
160
0
380
11956
0
0
0
0
0
40
40
0
0
0
0
0
203249
46904
156346
20
0
20
0
0
0
0
0
0
0
0
0
20
0
0
0
0
0
0
0
60
0
0
0
40
0
20
0
6438 5958
20
0
20
20
0
80
0
0
580
300
5518 5518
0
0
0
0
0
0
0
0
0
0
160
20
140
20
0
0
0
0
0
0
0
0
0
0
4598 22992
0
0
4598 22992
0
20
0
0
0
0
0
0
0
0
20
0
20
0
14495
40
120
160
0
340
13795
0
0
0
0
0
20
20
0
0
0
0
0
12876
0
12876
0
0
0
0
120
80
0
0
40
0
0
0
0
0
40
0
0
80
0
0
0
0
0
40
0
0
0
0
0
0
0
80
80
27
0
0
0
0
80
0
0
0
80
10756 13616 15215 9416
0
0
0
20
0
0
60
0
40
0
40
0
380
1840
560
10116 11496 14255
0
0
0
40
0
0
0
0
0
0
0
0
0
40
0
120
120
120
20
80
0
0
0
0
0
0
40
0
0
0
0
0
40
0
0
160
32189 1839 6898 22839
0
0
0
32189 1839 6898
563
Table 2. Composition and abundance of zooplankton (ind 1000 m-3) on the seamounts Juan Fernandez 1 and Juan Fernandez 2. Only the percentage of each taxonomic group is indicated.
Tabla 2. Composición y abundancia de zooplancton (ind 1000 m-3) en los montes submarinos Juan Fernández 1 y Juan
Fernández 2. Se indica solamente el porcentaje de cada grupo taxonómico.
Station
Species
Euphausiacea
Stratum (m)
1
2
3
4
(0-250)
(0-250)
(0-300)
(0-300)
5
6
7
(0-350) (0-268) (0-250)
8
Total
(0-250)
Percentage
(%)
1.29
2
4
118
35
7
9
158
9
342
Euphausia gibba
0
0
12
0
0
0
0
0
12
Euphausia gibboides
0
0
20
11
0
0
14
0
45
Euphausia mucronata
2
0
47
13
7
0
77
9
155
Euphausia sp.
0
0
12
0
0
0
24
0
36
Nematoscelis sp.
0
4
27
11
0
9
43
0
94
Mysidacea
0
0
0
11
11
0
5
0
27
0.10
Amphipoda
12
49
71
19
22
28
62
77
340
1.29
Vibilia armata
12
41
67
13
11
23
62
77
306
Acanthoscina acanthodes
0
4
4
3
7
0
0
0
18
Platyscelus sp.
0
4
0
3
4
5
0
0
16
Ostracoda
0
3
32
52
54
19
9
12
181
0.68
Copepoda
337
864
4338
2490
8917
1429
2766
1165
22306
84.38
Acartia sp.
4
33
39
21
254
28
38
0
417
Haloptilus longicornis
0
0
0
0
60
37
0
0
97
Haloptilus spiniceps
0
0
0
0
30
18
0
0
48
Haloptilus sp.
4
0
0
0
0
0
0
17
21
Calanus sp.
0
0
0
0
0
65
19
51
135
Canthocalanus pauper
24
17
125
118
0
0
0
0
284
Nannocalanus sp.
20
33
0
0
0
0
0
0
53
Candacia curta
0
0
8
0
0
0
0
26
34
Candacia sp.
4
17
0
75
15
18
0
0
129
Corycaeus sp.
8
17
55
0
30
0
10
0
120
Eucalanus inermis
0
0
0
0
30
28
0
0
58
Eucalanus sp.
4
50
16
0
0
9
77
17
173
Rhincalanus sp.
0
0
424
172
119
0
0
0
715
Euchaeta sp.
4
0
133
172
45
0
29
9
392
Heterorhabdus sp.
28
116
55
11
851
65
220
197
1543
Lucicutia sp.
4
17
24
43
30
111
134
77
440
Pleuromamma sp.
44
17
2031
0
2657
562
1148
308
6767
Pleuromamma borealis
4
66
0
976
0
0
0
0
1046
Oncaea conifera
8
0
149
86
0
9
19
26
297
Oncaea sp.
4
17
0
0
149
0
0
0
170
Oithona sp.
8
17
71
21
149
28
115
17
426
Pontellina sp.
0
0
0
0
0
0
19
0
19
161
364
643
236
3000
378
766
248
5796
Sapphirina sp.
4
50
0
32
15
18
19
120
258
Acrocalanus sp.
0
0
0
32
0
0
0
0
32
Paracalanus sp.
0
33
0
86
0
0
0
0
119
Clausocalanus sp.
564
Euaetideus sp.
0
0
0
0
75
0
0
0
75
Euchirella sp.
0
0
149
161
478
55
96
43
982
Gaudius sp.
0
0
165
139
239
0
57
9
609
Scaphocalanus sp.
0
0
251
97
687
0
0
0
1035
Scolecithrix sp.
0
0
0
12
4
0
0
0
16
Cirripedia
4
0
0
0
0
0
0
0
4
0.20
Decapoda (larvae)
0
0
0
3
4
0
0
0
7
0.03
Emerita analoga
0
0
0
3
4
0
0
0
7
Medusae
0
0
0
3
8
5
0
0
16
Cunina peregrina
0
0
0
3
0
0
0
0
3
Obelia spp.
0
0
0
0
4
0
0
0
4
Rophalonema velatum
0
0
0
0
4
5
0
0
9
Siphonophorae
6
4
59
59
34
23
101
13
299
Abylopsis tetragona
0
0
16
5
4
9
5
0
39
Eudoxoides spiralis
2
0
0
0
0
0
0
0
2
Dimophyes arctica
0
0
8
3
0
0
0
0
11
Lensia conoidea
0
0
0
3
7
0
0
0
10
Lensia hotspur
0
0
0
0
4
0
0
0
4
Lensia leloupi
0
0
0
0
4
0
5
0
9
Lensia sp.
0
0
0
0
4
0
5
4
13
Praya sp.
0
0
0
32
0
0
0
0
32
Sphaeronectes gracilis
2
0
35
16
11
14
86
9
173
Sulculeolaria chuni
2
0
0
0
0
0
0
0
2
Sulculeolaria quadrivalvis
0
4
0
0
0
0
0
0
4
Ctenophora
0
8
8
0
0
9
5
9
39
Beroe cucumis
0
4
0
0
0
0
0
0
4
Pleurobrachia bachei
0
4
8
0
0
9
5
9
35
Chaetognatha
88
141
393
249
198
216
153
119
1557
Eukrohnia hamata
8
21
71
32
93
37
19
17
298
Sagitta decipiens
0
0
0
48
0
0
0
0
48
Sagitta enflata
30
62
129
113
0
101
67
77
579
Sagitta hexaptera
8
0
12
0
19
0
0
0
39
Sagitta minima
0
0
118
5
19
0
5
0
147
0.06
1.13
0.15
5.89
Sagitta tasmanica
0
0
4
8
30
0
0
4
46
Juvenil individuals
42
58
59
43
37
78
62
21
400
Salpida
38
62
537
21
70
18
53
17
816
Ihlea magalhanica
28
17
110
21
63
9
53
0
301
Pegea confoederata
10
45
427
0
7
9
0
17
515
Appendicularia
8
8
4
8
45
9
5
4
91
0.34
Polychaeta
8
0
55
56
56
23
48
9
255
0.96
Nemertina
0
0
0
0
0
0
5
0
5
0.02
Pisces (eggs and larvae)
0
74
4
42
7
0
24
0
151
0.57
Hygophum bruuni
0
0
4
8
0
0
19
0
31
Sardinops sagax
0
74
0
21
7
0
0
0
102
Myctophidae
0
0
0
13
0
0
5
0
18
986
2423
11147
5969
18700
3525
6716
2843
52309
Total
3.09
100.0
565
Table 3. Invertebrate species collected with dredging.
Tabla 3. Especies de invertebrados recolectados con rastra.
Phylum/Class/Order
Number of samples
Phylum/Class/Order
Number of samples
Asteroidea
25
Ophiuroidea / Phynophiurida
3
Decapoda (spp.)
5
Polychaeta/ Terebellidae
12
Gastropoda (spp.)
6
Porifera + Ophiuroidea + Polychaeta
1
Echinoidea
38
Actiniaria + Polychaeta
1
Porifera (spp.)
34
Ophiuroidea
1
Gorgonia (spp.)
5
Porifera + Bryozoan + Polychaeta
1
Zoanthidea (spp.)
16
Lophophorates / Bryozoan
1
Holothuroidea
6
Bivalvia / Paleoheterodonta
1
Echinoidea/Echinacea (spp.)
142
Crustacea / Caridea
1
Actiniaria
27
Anthozoa / Actiniaria
3
Polychaeta (spp.)
55
Bivalvia (shell) (spp.)
6
Echinoidea + Ophiuroidea
6
Porifera + Polychaeta
3
Gorgonia / Ophioroida
10
Submarine images of the JF1 and JF2 marine substrate showed characteristics ascribed to the impact of
bottom dredges, coinciding with the information from
the trawling fleet, whose activity was primarily executed on the flat surface area of the seamounts (Gálvez
et al., 2006). When analyzed, this information revealed that the fishing activity was mainly concentrated on the JF2 seamount, reaching 4,667 km of
trawling; in comparison, trawling on the JF1 and JF4
seamounts reached values of 1,526 km and 906 km,
respectively. In spite of these results, the FEI showed
higher values for seamounts JF4 and JF2 (10.5 km-1
and 11.7 km-1, respectively) than for JF1. Although
heavy fishing activity was executed on the latter, its
FEI was 2.51 km-1 due to its larger area, which is estimated to be 608 km2 (Table 4).
Table 4. Name, mean latitude and longitude, and the estimated area, effort, and relative fishing effect index (FEI) of six
seamounts where extractive activity was conducted between 2000 and 2006.
Tabla 4. Nombre del monte, latitud y longitud media, área estimada, esfuerzo estimado e índice relativo de pesca (FEI) de
seis montes donde se efectuó actividad extractiva durante 2000-2006.
Seamount
JF1
JF2
JF3
JF4
JF5
JF6
Latitude
(S)
33°39.0'
33°33.6'
33°23.4'
33°26.4'
33°43.8'
34°04.8'
Longitude
(W)
78°26.4'
77°41.4'
77°25.2'
76°52.8'
79°37.2'
80°15.6'
In general terms, the fishing effort, measured as the
total trawling distance, increased considerably in
2002, 2003, and 2005, with values that exceeded the
Area
(km2)
608
443
62
91
17
s/i
Effort
(km)
1.526
4.667
395
906
50
s/i
FEI
(km-1)
2.51
10.54
6.42
11.70
1.52
s/i
500 km of trawling. Later, a considerable decrease
was observed by the end of the analyzed period (20012006), followed by the same values observed at the
566
beginning of the fishing activity. The high level of
observed fishing effort seems to have modified the
spatial structure of the resource aggregates exploited
at the JF2 seamount. In 2001, the aggregates at this
seamount showed a symmetrical spatial distribution
up to 4 km; however, that value that did not exceed 1
km in 2003 (Fig. 11). The spatial variability was affected by a decrease in the relative abundance of the
resources exploited on this seamount (orange roughy
and alfonsino) (Fig. 12).
Figure 11. Theoretical and adjusted spherical model for the catch rate variogram on seamount JF2 in 2001 and 2003.
Figura 11. Modelo esférico teórico y ajustado para el variograma de las tasas de captura en el monte submarino JF2 en
2001 y 2003.
Figure 12. Distribution of the catch rates for the seamount JF2 in 2001 and 2003; maps were generated by ordinary punctual kriging.
Figura 12. Distribución de las tasas de captura para el monte submarino JF2 en 2001 y 2003; mapas generados mediante
estimación espacial krigging puntual ordinario.
DISCUSSION
A total of 118 seamounts were identified in the continental and insular EEZ of Chile. A method similar to
that used by Kitchingman & Lai (2004) was put into
practice, considering statistical (standard deviation,
filters, hillshading) and visual (judgment, 3D cartography) analyses for the identification of potential seamounts. The number of identified seamounts is influenced by the depth standard deviation as well as filter
size and type (kernel 5*5 nearest-neighbor) and visual
analysis criteria. Furthermore, the identification sensitivity is directly affected by the spatial resolution of
the bathymetric data.
The information on the diversity of the phytoplankton organisms collected in the area, along with the
data analyzed by Pizarro et al. (2006), allow the preliminary inference that the nano- and microplankton
structure detected with the analysis of the water samples collected in late winter 2007 indicate the presence
of a clearly oligotrophic environment. Small organisms predominate such environments and the systems
are mainly supported by regenerated production and
the probable entry of allochthonous nutrients from
adjacent islands or elements advected from the seamounts or the coastal areas of Chile through large
upwelling plumes that are generally observed on satellite images. Regarding the diversity of zooplankton
organisms, most species and/or genera identified
around the seamounts corresponded to organisms that
are characteristic of the oceanic waters of the Humboldt Current System, which are found in low densities off the coast. The taxonomic composition of the
zooplankton in this area is characterized by the presence of copepods (84.4% zooplankton), which coincides with results for oceanic waters in similar ecosystems of other oceans (Schnack-Schiel & Mizdalski,
2002). The quantity of zooplankton was quite scarce,
in agreement with the low densities reported around
the Juan Fernandez Archipelago (Palma, 1985) and
the oceanic waters along the Chilean coast (Palma &
Silva, 2006), and with other studies that have shown
low densities on seamounts with abrupt topographies.
This contradicts the results of Schwartz (2005) for
seamounts from the Eastern Central Pacific. In fact,
the biomass values were quite low compared to those
detected in Chile’s coastal waters.
The diversity of pelagic, demersal, and benthic organisms from this area was restricted to four fish species and two crustacean species. This was basically
due to the fishing systems used in the surveys, which
prioritized direct, non-intrusive sampling methods
such as submarine images and gears like traps and
567
longlines. One fish was the blue shark (Prionace
glauca), a species considered to be epipelagic and of
circumpolar distribution (Compagno, 1984). This
shark is abundant in the southeastern Pacific and is
captured by multiple fleets using surface longlines.
The sawfish (Thyrsites atun), on the other hand, is
considered to be a benthopelagic fish with a wellknown distribution on continental shelves or around
islands (Nakamura & Parin, 1993). Among demersal
fish, the croaker (Helicolenus lengerichi) has been
cited as one of the five species of the Scorpaenidae
family present around the Juan Fernandez Archipelago
(Pequeño & Sáez, 2000), whereas the conger Bassanago albescens has been caught with a low incidence (Lillo et al., 1999) as part of the by-catch of
orange roughy fishing activities on Juan Fernandez
seamounts.
The golden crab (Chaceon chilensis) and the Juan
Fernandez king crab (Paromola rathbuni) have been
cited as two of the five decapod crustacean species
captured during surveys and experimental trap fishing
activities around Robinson Crusoe and Santa Clara
islands (Retamal & Arana, 2000). The presence of the
Juan Fernandez king crab was originally reported for
the Juan Fernandez Archipelago (Retamal, 1981) and
the Desventuradas Islands (Báez & Ruiz, 1985) and is
considered to be endemic to this area of the southeastern Pacific. This decapod is distributed between 100
and 300 m depth, with a greater abundance at 200 m
around Robinson Crusoe and Santa Clara islands (Retamal & Arana, 2000). Furthermore, the golden crab
has been reported off Zapallar and Quintero, along the
central coast of continental Chile (Báez & Andrade,
1977; Andrade & Báez, 1980; Andrade, 1987), the
Juan Fernandez Archipelago and San Félix and San
Ambrosio islands (Retamal, 1981; Chirino-Gálvez &
Manning, 1989), and along the undersea Nazca Ridge
mainly at 90°W (Parin et al., 1997). The golden crab
is generally distributed between 200 m and 2,000 m of
depth (Dawson & Webber, 1991). It was found at
depths of 400 and 800 m along the undersea Nazca
Ridge (Parin et al., 1997) and was caught at 100 and
1,000 m around Robinson Crusoe and Santa Clara
islands, with a greater abundance at 300 m and between 500 and 600 m (Arana, 2000).
The submarine images of the plains of seamounts
JF1 and JF2 (up to 600 m approximately) suggest the
presence of a marine substrate with similar characteristics to those reported in the literature for places that
have been strongly impacted by trawling gears (FAO,
2007; Clark & Koslow, 2007).
Johnston & Santillo (2004) have suggested that
sustainable seamount fisheries require good knowledge of the biology and ecology of the species to be
568
exploited. Regarding the orange roughy fisheries on
seamounts within the Chilean EEZ, there has been a
trend towards increased global quotas in spite of the
ignorance regarding the stock abundance at the Juan
Fernandez Archipelago (Young et al., 2000; Gálvez et
al., 2006). Despite this increase, the quota has never
been totally extracted and the landing proportion has
been observed to decrease.
The FEI provides a measure of relative intensity of
the trawling fishing activities on a seamount, thereby
allowing the categorization of the seamounts according to trawling density and direction. Due to the fact
that the trawling was reported to last close to a minute
and the trawling velocity is generally constant, then
the trawling length estimation offers an adequate indicator of the scanned area. The distribution of the
trawling direction on the studied seamounts was not
random, suggesting that the fishermen have some
degree of knowledge and, thus, prefer certain areas
(trawling routes), whereas other adjacent areas do not
seem to be affected by fishing activities. O’Driscoll &
Clark (2005) have suggested that the FEI cannot directly assess the fishing impact on a seamount. Therefore, it should be necessarily related to other ecological indexes in order to obtain an ecological impact
index of the trawling fishing over the substrate and
associated fauna that could vary according to the substrate and fishing intensity.
Furthermore, strong spatial variability of the relative densities of the fishing resources associated with
seamount JF2 in 2001 and 2003 was observed. This
spatial variability was associated with a decrease in
the relative abundance of the two main fishing resources exploited on this seamount (orange roughy
and alfonsino) and a strong spatial contraction of said
resources, which was represented by a significant
change in the variogram range. The effect of the
commercial exploitation on seamount JF2 caused an
85% reduction in the range of values between 2001
and 2003. Pankhurst (1998) indicated that orange
roughy aggregates in the same period and place on the
seamounts of New Zealand, which makes it quite
predictable. These dense aggregations cause an elevated backscattered acoustic amplitude that is easily
identified. Thus, the resource is highly vulnerable to
commercial fishing. Besides, it has also been suggested that, during productive periods, orange roughy
aggregations tend to remain still during certain periods
or even for many days (Bull et al., 2001).
One of the objectives of the current international
approach for marine biodiversity conservation is the
identification and protection of the discrete areas that
are defined from the representativeness of the existing
ecosystems and/or their role as an essential habitat for
the conservation of vulnerable or threatened species.
Therefore, the demand for the identification and prioritization of possible protected marine areas in the
Chilean seamounts requires some knowledge of the
structure and singularity of its communities and the
role such areas play in the life cycle of the species
identified as special conservation subjects. In this
sense, the extent of the knowledge necessary for the
adequate conservation of biodiversity on seamounts in
the Chilean EEZ is huge and this study is just one step
towards an increase in the available information. Obviously, most attention is directed towards those areas
currently under fishing exploitation, where it is crucial
to take conservation measures for the development of
sustainable activities.
ACKNOWLEDGEMENTS
The authors would like to thank the crews of PAM
Portugal II, the L/M Alborada, and the boat Cumberland for their great disposition and assistance with the
works carried out on board. Furthermore, we wish to
thank the Fondo de Investigación Pesquera de Chile
for their support of FIP project No. 2006-57.
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Golden crab fisheries off northeast Brazil
571
Short Communication
Note on the fisheries and biology of the golden crab (Chaceon fenneri)
off the northern coast of Brazil
Tiago Barros Carvalho1, Ronaldo Ruy de Oliveira Filho1 & Tito Monteiro da Cruz Lotufo1
1
Laboratório de Ecologia Animal, Instituto de Ciências do Mar (LABOMAR)
Universidade Federal do Ceará, Av. Abolição 3207, CEP 60165-081, Fortaleza, CE, Brazil
ABSTRACT. The occurrence of golden crabs (Chaceon fenneri) off the northern coast of Brazil was first reported in 2001. Since then, a few companies and boats have exploited this resource. In the state of Ceará, one
company has been fishing for these crabs with a single boat since 2003. The production and fishing effort of
this company indicated a decrease in the number of trips and total catches per year. Data collected on one trip
in 2006 showed that the CPUE was highest at over 650 m depth. As registered for other geryonid crabs, C.
fenneri was segregated by sex along the northern slope of Brazil. Male crabs were significantly larger than females, presenting an isometric relationship between carapace width and length and an allometric relationship
between carapace width and body weight.
Keywords: biology, fishery, Chaceon fenneri, golden crab, Geryonidae, Brazil.
Nota sobre la biología y la pesca del cangrejo dorado (Chaceon fenneri)
frente a la costa norte de Brasil
RESUMEN. La presencia de cangrejos dorados (Chaceon fenneri) frente a la costa norte de Brasil fue primeramente descrita en 2001. Desde entonces, algunas embarcaciones y compañías se han dedicado a explotar este recurso. En el Estado de Ceará, una sola compañía ha estado pescando estos crustáceos desde el año 2003
con una sola embarcación. Se presenta la producción y esfuerzo pesquero aplicado por esa compañía, indicando la disminución en el número de viajes y captura total por año. Registros recolectados en un viaje realizado
el 2006 muestran que los mayores valores de CPUE se obtienen a profundidades mayores de 650 m. Al igual
que lo registrado en otros Geryonidae, agregaciones por sexo se determinaron en C. fenneri a lo largo del talud
en la región norte de Brasil. Los machos fueron significativamente más grandes que las hembras, presentando
una relación isométrica entre el ancho y longitud del caparazón; como también, una relación alométrica entre
el ancho y el peso.
Palabras clave: biología, pesca, Chaceon fenneri, cangrejo dorado, Geryonidae, Brasil.
________________________
Corresponding author: Tito Monteiro da Cruz Lotufo ([email protected])
Chaceon fenneri (Manning & Holthuis, 1984) is a
geryonid crab (Brachyura: Geryonidae) occurring on
the western Atlantic from the Gulf of Mexico to
northeast Brazil. As all the other Geryonidae, C. fenneri is found along the continental slope between 200
and 1500 m deep. These animals present the usual
Chaceon features, such as a large hexagonal cephalothorax ranging in width from 7.5 to 20 cm, ornamented by five antero-lateral teeth on each side, and
distinguished by its cream to tan color, with laterally
compressed dactyls on the walking legs (Manning &
Holthuis, 1989).
Geryonid crabs are found throughout the planet
oceans, except for the east Pacific, in depths ranging
from around 100 m to more than 2800 m (Manning,
1990). The family comprises four genera and 24 species, many of them of commercial importance to industrial and artisanal fisheries. In Brazil, fishing for
572
geryonid crabs started in the 1980s. Incipient efforts
were restricted to the southeast/south coast and targeted Chaceon ramosae and Chaceon notialis, and
were only definitely established in the late 1990s,
stimulated by government policies (Pezzuto et al.,
2006). C. notialis is distributed south to 33ºS, reaching
Argentina, and is the most important geryonid in terms
of Brazilian fisheries, with an estimated stock of
17,117.80 tons (Pezzuto et al., 2002). C. ramosae is
found between 27ºS and 30ºS, and almost half of the
reported production comes from gill nets instead of
the usual traps (Pezzuto et al., 2006).
The first record of C. fenneri from Brazil was presented by Sankarankutty et al. (2001), based on
specimens collected during a survey of the REVIZEE
Program on the northeast coast. Since then, a few
fishing boats from Natal and Fortaleza harbors have
targeted the species. Today, only one company (based
at Fortaleza) is known to be exploiting this resource,
dedicating a single boat to this fishery.
This study describes the C. fenneri fishery off the
coast of Ceará, presenting data on a few biological
descriptors such as size structure, sex ratio, and spatial
and bathymetric distribution.
The data related to production were obtained from
the Interfrios Company, comprising the period between April 2003 and August 2007. Data regarding
population estimations were obtained onboard the crab
fishing boat, Incopesca I, property of Industria Naval
do Ceará (INACE), from 19 to 23 July 2006. The
fishing stations were located about 40 nm north of the
Ceará coast, and were determined by the boat’s crew
with the aid of charts, GPS, and sonar. During five
days of fishing, the traps were deployed nine times at
six different stations (Fig. 1). The traps used were
circular, with an iron structure and a 9-mm PE (polyethylene) net; they were baited with fish carcasses. A
total of 198 traps were used (65 traps per fishing station). On average, the traps were soaked for 17 h (deployment to retrieval) at sites with depths ranging
from 500 to 800 m.
Once the traps were retrieved, the boat’s crew
visually selected the crabs and all small crabs (CW <
~12.5 cm) were released. For each trap, we recorded
the total number of crabs of each sex that were caught
and released. After landing, the individuals were
measured for carapace length (CL) and width (CW)
using a caliper and weighed on an electronic semianalytic scale (0.001 g precision). The CW was measured including the lateral spines. The CPUE was calculated in terms of the mean number of crabs caught
per trap and the effective CPUE (CPUE eff.) using
only the number of processed crabs. Statistical analy-
ses were done with the software Statistica 7.0 (Statoft
Inc.) and JMP 7.0.1 (SAS Institute Inc.).
From April 2003 to August 2007, a total of 37 fishing trips were conducted, resulting in 41,794 kg of
golden crabs, for an average of 1,478.13 kg trip-1 (Table 1).
The data on crab production from 2003 to the present show an irregular downward trend in effort and
production. It is worth noting that Table 1 shows only
the number of trips, since the company did not provide
the number of days at sea or amount of traps deployed
per trip. On the other hand, even considering large
differences in effort per trip, an average of only five
trips were conducted in each of the last four years.
Until 2003, almost all production was exported,
mainly to European countries, an activity that was
favored by the currency exchange rates at that time. In
2004, the economic setting changed and the Brazilian
currency appreciated strongly, impacting many activities such as shrimp and crab exportations. The fishing
company tried to boost the local market with a feeble
campaign restricted to Fortaleza, where the consumption of mangrove crabs (Ucides cordatus) is the largest in Brazil. In the following years, INACE kept fishing for crabs in an attempt to maintain the commercial
channels opened. Today, golden crabs are sold to
states in the southeast/south (São Paulo, Rio de Janeiro, and Paraná) and are exported to the United
States of America.
Biologically, the data obtained so far reveal many
similarities with other geryonid crabs. Table 2 shows
the deployment depths of the traps, number of traps
used, CPUE, and numbers of males and females captured and released. Males and females show a tendency for bathymetric segregation (χ2 = 2806.26, d.f.
= 8, p < 0.000001), with males being more frequent at
deeper sites and females more common in shallower
areas. In the south Atlantic Bight, Wenner (1990)
found a different pattern for this species, with more
abundant males between 274 and 549 m depth and
females predominating at the deeper sites (733-823
m). On the other hand, Lindberg & Lockhart (1993)
showed that, in the Gulf of Mexico, Chaceon fenneri
followed the same pattern found in Brazil. In Chaceon
notialis, a species fished in more austral waters of the
western Atlantic, females were also concentrated in
shallower areas (Defeo et al., 1991). Pinho et al.
(2001) reported that the situation of Chaceon affinis in
the Azores was similar to that described by Wenner
(1990) for C. fenneri in the south Atlantic Bight, with
males dominating in shallower areas. Gender segregation was also registered for other geryonids (Lindberg
& Lockhart, 1993; Pinho et al., 2001; López-Abellán
et al., 2002), and it seems that the distribution of these
573
Figure 1. Location of the fishing stations for golden crabs off Ceará coast, Brazil.
Figura 1. Localización de los lugares en donde se realizaron las faenas de pesca frente a la costa de Ceará, Brasil.
Table 1. Yearly data on the number of fishing trips and amount of golden crabs caught off the Ceará coast.
Tabla 1. Datos anuales correspondientes al número de viajes de pesca y cantidad de cangrejos dorados frente a la
costa de Ceará.
Year
Number of trips
-1
Average (kg trip )
-1
Total (kg year )
2003
2004
2005
2006
2007
16
03
08
04
06
1,478
1,503
783
1,033
540
23,650
4,510
6,263
4,131
3,240
species may be affected by their reproductive cycle or
other unknown conditions.
In the north Atlantic, C. fenneri co-occur with another Chaceon species: C. quinquedens. The bathymetric distributions of these two species overlap, with
C. quinquedens occurring mainly at deeper sites
(Lindberg & Lockhart, 1993). In Brazil, no other
geryonid species are captured in the traps, only the
giant isopod Bathynomus giganteus. As no competitors seem to be present, the bathymetric range of C.
fenneri in Brazil may extend to deeper limits.
In a subsequent attempt to capture golden crabs in
February 2007, traps were mistakenly deployed at 450
m and only ovigerous females were caught; these were
promptly released. On the same trip, attempts between
650 and 820 m depth were unsuccessful and not a
single specimen was caught. This may indicate the
reproductive period of C. fenneri in Brazil, although
much more data are needed to support this. In southeastern Florida, the oviposition period of golden crabs
occurs between August and October, with an incubation time of approximately six months, for hatching in
574
February and March (Erdman & Blake, 1988). Other
authors have also reported a bathymetric migration of
females related to the reproductive period (Lindberg et
al., 1990; López-Abellán et al., 2002). If female
golden crabs indeed migrate to shallower areas for
oviposition or hatching, the establishment of exclusion
depth ranges may constitute an important measure for
resource administration.
Table 2 shows that about 42% of the females were
released, compared to only 10% of the males. Although the overall sex ratio was almost 1:1, the activity has a greater impact on males, especially due to
their larger sizes.
Regarding the CPUE, Table 2 shows that the best
results were obtained at the deeper sites. These data
must be analyzed carefully given the small number of
sites and depths analyzed. At depths shallower than
650 m, the average CPUE was 2.975 crabs trap-1 (S.E.
= 0.890) whereas, at the deeper sites (≥ 650 m), the
average CPUE was 3.552 crabs trap-1 (S.E. = 0.397).
All sites were located at depths beyond 580 m, so it
was not possible to compare the bathymetric distributions between Ceará and the north Atlantic. Wenner
(1990) studied the bathymetric distribution of C. fenneri in the south Atlantic Bight, pointing out that
maximum yields (12 crabs trap-1) were obtained in the
458-549 m range. Later on, Lindberg & Lockhart
(1993) found a larger density of C. fenneri in the Gulf
of Mexico between 350 and 550 m, with the largest
animals being captured at 350 m depth. More recently,
Harper et al. (2000) reported that the golden crab fishery in the Gulf of Mexico from 1995 to 2000 targeted
mostly sites between 300 and 500 m deep. Future
prospection must be conducted at these depths in order
to establish the bathymetric distribution of this species
along Brazil’s northeast continental slope.
Since the fishing effort on the golden crab stock of
the Brazilian northern slope is still very small, the
prospects in terms of resource administration are
good. Although the volume of data regarding the
population of golden crabs along Brazil’s northern
continental slope is scanty, more data can be gathered
in order to estimate the maximum sustainable yield
and establish the rules for this fishery.
As for the sizes of the animals, Table 3 summarizes the variables measured. These data are biased
and by no means represent the natural population.
Males are consistently larger and heavier than females, corroborating the values presented by
Sankarankutty et al. (2001). The average CL and CW
shown in Table 4 are almost the same as those obtained by Harper et al. (2000) in the Gulf of Mexico.
For males, the relationship between CW and CL
indicates isometric growth, as shown by the regression
Table 2. Fishing depth, number of traps deployed, and amount of C. fenneri males and females caught during one fishing
trip. The CPUE is presented in terms of captured (CPUE) and processed crabs (CPUE eff.).
Tabla 2. Profundidad de pesca y número de trampas caladas y cantidad de machos y hembras de C. fenneri en un viaje de
pesca. La CPUE está presentada en términos de captura (CPUE) y de cangrejos procesados (CPUE eff.).
Set #
Depth
(m)
Males
Females
Released
males
Released
females
Total
captured
Total
released
Total
processed
No.
traps
CPUE
CPUE
eff.
1
650
208
28
9
14
236
23
213
71
3.32
3.00
2
580
72
281
10
253
353
263
90
65
5.43
1.39
3
640
144
18
3
10
162
13
149
62
2.61
2.40
4
650
61
106
5
31
167
36
131
71
2.35
1.85
5
580
61
114
7
20
175
27
148
65
2.69
2.28
6
650
29
211
0
19
240
19
221
64
3.75
3.45
7
680
153
76
11
12
229
23
206
65
3.52
3.17
8
790
256
91
52
35
347
87
260
72
4.82
3.61
9
580
15
60
1
20
75
21
54
64
1.17
0.84
999
985
98
414
1984
512
1472
599
Total
575
Table 3. The mean, standard deviation, mode, and median for carapace width (CW), carapace length (CL), and the weight
of golden crabs captured off the Ceará coast.
Tabla 3. Media, desviación estándar, modas y mediana en el ancho del caparazón (CW), largo del caparazón (CL) y peso
de los cangrejos dorados capturados frente a la costa de Ceará.
Mean
Standard
deviation
Mode
Median
Males
(N = 87)
CW (cm)
CL (cm)
Weight (g)
14.56
12.64
980.17
0.91
0.82
209.97
14.4
12.9
858
14.4
12.7
970
Females
(N = 23)
CW (cm)
CL (cm)
Weight (g)
13.56
11.77
701.70
0.75
0.58
70.75
14.5
12.4
720
13.40
11.80
720.00
presented in Figure 2 (CL = 0.2831992 + 0.8484187 ·
CW; R2 = 0.89). The regression with weight, on the
other hand, indicates an allometric relationship (Fig. 3;
Weight = 0.2263566574 CW3.1212672783; R2 = 0.83).
The data available for females was insufficient for the
same analysis. It is worth noting that the values used
for these calculations are restricted to large adults
processed by the fishing company.
A more thorough investigation on the size structure
of the population, spatial and bathymetric distribution,
and reproductive biology is required for a correct
management of this resource. As this population has
not yet been strongly targeted by fisheries, the need
for further data is urgent.
Figure 3. Regression of carapace width (CW) vs. weight
for male golden crabs caught off the Ceará coast.
Figura 3. Regresión entre el ancho del caparazón y el
peso en machos de cangrejos dorados capturados frente a
la costa de Ceará.
ACKNOWLEDGEMENTS
The authors are deeply indebted to Industria Naval do
Cerará (INACE) and Interfrios for providing data and
making this study possible, and to Luiz Bezerra for the
help with the map. The authors also wish to thank Dr.
Paulo Pezzuto and two anonymous referees for their
thoughtful comments on the manuscript.
Figure 2. Scatter plot of carapace width (CW) vs. carapace length (CL), with regression lines and confidence
curves for male golden crabs collected off Ceará coast.
Figura 2. Gráfico con las mediciones de ancho del caparazón (CW) vs largo del caparazón, con líneas de regresión y curvas de confianza, en cangrejos dorados capturados frente a la costa de Ceará.
REFERENCES
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576
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s - Latin American Journal of Aquatic Research

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