Environmental impacts of alien species in

Transcription

Project no.: 044142
Project acronym: IMPASSE
Environmental impacts of alien species in aquaculture
COORDINATION ACTION
PRIORITY FP6 2005-SSP-5A
SUSTAINABLE MANAGEMENT OF EUROPE’S NATURAL
RESOURCES
D2. Analysis of the impacts of alien species on aquatic ecosystems
Due date of deliverable: 30.11.2007
Actual submission date: 08.03.2008
Start date of project:
01.12.2006
Duration: 24 months
Organisation name of lead contractor for this deliverable:
GOCONSULT
Responsible authors: Stephan Gollasch, Ian G. Cowx, A.D. Nunn
Version 1
Project co-funded by the European Commission within the Sixth Framework Programme (2002-2006)
Dissemination Level
PU
PP
RE
CO
Public
Restricted to other programme participants (including the Commission Services)
Restricted to a group specified by the consortium (including the Commission
Services)
Confidential, only for members of the consortium (including the Commission
Services)
Deliverable 2.5
Impasse Project No 44142
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Contents
1
Introduction
1
2
Summary of case studies / fact sheets
4
2.1
Overview
4
2.2
Summary assessment
4
2.3
Decisions on inclusion in Annex IV
3
Alien species fact sheets
16
Crassostrea gigas (by Laurence Miossec)
Ruditapes philippinarum (by Philippe Goulletquer)
Astacus leptodactylus (by F Gheradi)
Pacifastacus leniusculus (by I.G. Cowx and A.D.Nunn)
Procambarus clarkii (by F Gheradi)
Macrobrachium rosenbergii (by Anna Occhipinti Ambrogi)
Penaeus indicus (by D Stephanou)
Marsupenaeus japonicus (by Dario Savini Anna Occhipinti
Laurence Miossec and Emili García-Berthou)
Sturgeons (by Jiri Musil)
Argyrosomus regius (by I.G. Cowx and A.D.Nunn)
Hypophthalmichthys nobilis (by R.E. Gozlan and K. Lawrie)
Carassius auratus ((by G.H. Copp, I.G. Cowx and A.D.Nunn)
Clarias gariepinus (by I.G. Cowx and A.D.Nunn)
Coregonus peled (by Unto Eskelinen)
Ictalurus punctatus (by I.G. Cowx and A.D.Nunn)
Lates calcarifer (by I.G. Cowx and A.D.Nunn)
Mylopharyngdodon piceus (by Ion Navodaru and Aurel Nastase)
Oncorhynchus kisutch (by I.G. Cowx and A.D.Nunn)
Oreochromis niloticus (by I.G. Cowx and A.D.Nunn)
Polyodon spathula (by I.G. Cowx and A.D.Nunn)
Salvelinus fontinalis (by K. Bygrave, I.G. Cowx and A.D.Nunn)
Salvelinus namaycush (by I.G. Cowx and A.D.Nunn)
Sander lucioperca (by I.G. Cowx and A.D.Nunn)
Silurus glanis (by I.G. Cowx and A.D.Nunn)
Hypophthalmichthys molitrix (by R.E. Gozlan and K. Lawrie)
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1
INTRODUCTION
Council Regulation (EC) No 708/2007 of 11 June 2007 concerning use of alien and locally
absent species in aquaculture includes a list of species as Annex IV that are exempted from
the application of the principles in this Council Regulation. This refers to species already
introduced into the Community, e.g. species imported in current commercial practice. For a
species to be exempt, it must have been used in aquaculture for a long time (with reference
to its life cycle). At the same time it should be documented that the species show no adverse
effects, i.e. introductions and translocations of such species must avoid unintentional
movements of potentially harmful non-target species, such as disease agents and other
"fellow travellers". Annex IV of this EU instrument provides a list of such species and
Member States may request the Commission to add species to this list.
Current Annex IV contains 12 species (Table 1) that are already exempt because they have
been used in aquaculture in the EU for considerable time and represent important species for
production. A further 30 species (Table1) have been proposed for inclusion in Annex IV but
these require assessment of their importance in European aquaculture as well as whether
they are likely to have any significant impacts if given exemption to the principles of Council
Regulation 708/2007.
The criteria against which species were assessed are:
(a)
The aquatic organism must have been used in aquaculture for a long time (with
reference to its life cycle) in certain parts of the Community with no adverse effects in
the wild.
Long time means a minimum period of 10 years after two production cycles are
completed. This time period is considered the minimum period necessary to observe
any adverse effects on ecological goods and services and ecosystem functioning.
Adverse ecological effect on the recipient ecosystem is defined as where evidence
shows that an aquatic species, after its introduction in a particular country, has
caused inter alia habitat degradation, competition with native species for spawning
habitat, or hybridization with native species threatening species integrity, or predation
on native species’ population resulting in their decline, or depletion of native food
resources.
Notes: Due recognition should be given to:
• species proposed by MS that would not reproduce within their jurisdiction but
could become established in other European regions (climatic zones).
• Species with widespread distribution or native in certain parts of Europe are
exempt from the criterion. This is to avoid MSs having to apply for a licence
each time a species is introduced, where the species is native to certain parts
of Europe but is now widely distributed (e.g. pikeperch) or where the species
is widely farmed and distributed across Europe (e.g. rainbow trout).
(b)
Introductions and translocations must be able to take place, without the coincident
movement of potentially harmful non target species (having regard to the fact that
diseases-causing organisms are covered by Directive 2006/88/EC).
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Table 1. Species included or under consideration for inclusion in Annex IV
Included in Annex IV
Rainbow trout
Brook trout
Common carp
Grass carp
Silver carp
Big head carp
Pacific cupped oyster
Japanese or Manila clam
Large-mouth bass
Arctic char
Under consideration for inclusion
Oncorhynchus mykiss
Salvelinus fontinalis
Cyprinus carpio
Ctenopharyntgodon idella
Hypophthalmichthys molitrix
Hypophthalmichthys (Aristichtys) nobilis
Crassostrea gigas
Ruditapes philippinarum
Micropterus salmoides
Salvelinus alpinus
1. Pike-perch / zander
2. European perch
3. Vendace / whitefish spp
4. Sturgeon spp
4.1 Siberian sturgeon
4.2 Starry sturgeon
4.3 Russian sturgeon
4.4 Starlet sturgeon
4.5 Fringebarbel sturgeon
4.6 Atlantic sturgeon
4.7 Beluga sturgeon
5. Tench
6. Crucian carp
7. River / lake + sea trout
8. Meagre / maigre
9. Great lake / American trout
10. European catfish / wels catfish
Sander (Stizostedion) lucioperca
Perca fluviatilis
Coregonus sp
11. African catfish
12. Nile tilapia
13. Goldfish
14. Danube salmon
15. Coho salmon
16. Airbreathing catfish
17. Channel catfish
18. Red tilapia (aurea)
19. Asp
20. Mozambique tilapia
21. Red drum
22. Black kingfish
23. Barramundi
24. Black carp
25. Mississippi/American paddlefish
26. Giant river prawn
27. Signal crawfish
28. Red swamp crayfish
29. Danube crayfish
30. Kuruma prawn
Clarias gariepinus
Oreochromis niloticus
Carassius auratus
Hucho hucho
O. kisutch
Clarias spp.
Ictalurus punctatus
O. aureus
Aspius aspius
O. mossambicus
Sciaenops ocellatus
Rachycentrum canadum
Lates calcarifer
Mylopharyngodon piceus
Polyodon spathula
Macrobrachium rosenbergii
Pacifastacus leniusculus
Procambarus clarkii
Astacus leptodactylus
Penaeus japonicus
Deliverable 2.5
Acipenser baeri
A. stellatus
A. gueldenstaedtii
A. ruthenus
A. nudiventris
A. sturio
Huso huso
Tinca tinca
Salmo trutta
Argyrosomus regius
Salvelinus namaycush
Siluris glanis
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As part of the actions to evaluate whether a species should be included for exemption, a
series of fact sheets were prepared for discussion at expert workshops held in Brussels and
subsequent decision on their inclusion. This document provides a summary of the fact
sheets and the conclusions from the deliberations.
More than 30 species fact sheets were prepared (see Section 3), which summarise
information on diagnostic features, geographical distribution, habitat and biology, aquaculture
production (with an emphasis on the European industry), impacts of introduction, factors
likely to influence spread and distribution. The fact sheets may be consulted for further
details. These documents also provide extensive case studies of the negative (and
beneficial) impacts of selected alien species, thereby contributing to the outputs of WP2. As
such they represent a major output of IMPASSE WP1 (Task 1.2 - aquaculture production)
and WP2.
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SUMMARY OF CASE STUDIES / FACT SHEETS
2.1
Overview
The majority of the species considered have reported impacts that are both adverse and
beneficial. The main benefits are derived from aquaculture production or improved sport
fishing / angling experience, both of which generate income and create employment, albeit
mostly on a local scale. The only species with no known adverse impact are sturgeons.
Owing their very low numbers a predatory impact is neglectable. However, the risk or
disease and / or pathogen transfer remains. The species with the greatest impact are the
pacific oyster, Crassostrea gigas, the North American signal crayfish, Pacifastacus
leniusculus, and the Nile tilapia, Oreochromis niloticus.
Although some species do not (yet) show an impact in Europe, negative consequences are
known from other regions where the species was also introduced. The range of known
impacts for the species included or considered for inclusion in Annex IV are summarised in
Figure 1. The highest assumed and /or documented impact risks are competition with native
species (including competition for food and other resources), predation and disease transfers
(Table 2).
competition
disease transfer
11%
erosion
2%
fouling
genetics
9%
41%
37%
Figure 1. Impact or potential impact of species selected to the fact sheets.
2.2
Summary assessment
Crassostrea gigas - settles in dense aggregations in the intertidal zone, resulting in the
limitation of food and space available for other species. In several countries, including
northern Europe, uncontrolled natural reproduction led to a significant species expansion and
natural breeding stocks. Positive and negative effects have resulted from habitat changes
through reef building capacity:
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Crassostrea gigas
Type
of impact
Species
Displacement of native species
Competing for food and space
Benthic-pelagic interactions
Food web modifications
Habitat change
Hydridization
Transfer of parasites, diseases
Introduction of "fellow species"
Increased erosion
No adverse impact known
x
x
x
x
x
x
x
x
Total number of
impact types
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2
x
x
x
1
x
x
4
x
x
x
x
3
x
2
x
1
1
x
0
x
2
x
x
x
2
x
x
x
x
x
x
x
x
x
3
3
1
x
x
3
1
2
3
x
x
x
x
x
x
x
x
x
x
4
3
1
Sander lucioperca
x
x
x
Silurus glanis
Hypophthalmichthys molitrix
Sciaenops ocellatus
Rachycentron canadum
Polyodon spathula
x
x
x
x
Oncorhynchus kisutch
x
Mylopharyngdodon piceus
Lates calcarifer
Ictalurus punctatus
x
Coregonus peled
x
Clarias gariepinus
Carassius auratus
Hypophthalmichthys nobilis
Argyrosomus regius
Sturgeons
Marsupenaeus japonicus
Penaeus indicus
Macrobrachium rosenbergii
Procambarus clarkii
Table 2. Types of impact as per species fact sheets
x
x
x
x
x
x
x
x
2
3
2
1
3
5
•
•
•
•
•
•
•
displacement of native species where the Pacific oyster develops breeding
populations and became an invasive species,
competing for food and space by building massive oyster beds through its natural
spat settlement and recruitment;
benthic-pelagic interactions and likely food web modifications;
habitat change;
hydridization with local oyster species;
transfer of parasites, diseases and pest species concomitant to oyster transfer.
introduction of "fellow species". It is acknowledged that the macrophyte algae
Sargassum muticum was introduced concomitantly to oyster spat in European
waters. Several other fouling species are known to be accidentally introduced with
oysters.
Ruditapes philippinarum -the Manila clam may have a negative impact on native species
due to competition for resources, especially during mass developments. They are further
known as carrier of various pathogens and disease agents (e.g. Herpes-like virus,
Rickettsiosis, Vibrio tapetis, Perkinsus-like organisms and Perkinsus olseni, Cercaria elegans
and Cercaria tapidis, Proctoeces orientalis).
Astacus leptodactylus - No in-depth studies have been conducted to assess the ecological
impacts of Astacus leptodactylus introductions but it is an invasive species and can form
dense populations. Due to its large size and high fecundity, it may displace other crayfish
species in the same water-body. It has been recorded as displacing A. astacus. In Britain,
where A. leptodactylus has been introduced and is now common in the wild, it has been
declared as a pest. It is not permitted to keep it without a licence.
Pacifastacus leniusculus - The disruption caused by P. leniusculus to ecosystems is quite
variable. In Europe, P. leniusculus occupies the same ecological niche as native crayfish
species and has caused the extirpation of populations of native crayfish populations,
particularly the endangered white-clawed crayfish (Austropotamobius pallipes. Pacifastacus
leniusculus is an opportunistic polytrophic feeder that may exert significant grazing pressure
on macrophytes, or predation on aquatic insects, snails, benthic fishes and amphibian larvae,
including native crayfish species. In closed water systems P. leniusculus is documented as
impacting far more heavily by grazing on flora and fauna that are not replaced as readily as
they would be in an open system.
In Europe, P. leniusculus had developed the habit of burrowing into bank sides. This
activity can have a detrimental effect in the form of weakened bank sides that become
increasingly susceptible to erosion. Farmers have also been cited as victims because
livestock are injured when stepping into the burrows and breaking limbs. Pacifastacus
leniusculus is also thought to pose considerable threat to migrating Atlantic salmon as not
only is it a keen devourer of the eggs and fry of this fish, it also competes for the same
shelter during the moulting period when the animal is soft bodied and therefore more
vulnerable to predators. The main impact of introducing P. leniusculus has been as a vector
of the crayfish plague fungus, Aphanomyces astaci, which has caused large-scale mortalities
amongst indigenous European crayfish populations, particularly in England. There are no
reported incidents of hybridisation of P. leniusculus and other crayfish but the physiological
similarities of P. leniusculus with A. astacus allow them to mate, although the eggs are
infertile.
Procambarus clarkia - Once introduced into areas without any indigenous ecological
equivalent, P. clarkii usually affects all levels of ecological organization. Its impacts range
from subtle behavioral modifications of resident species to altered energy and nutrient fluxes
in the ecosystem. Impacts at the community level can be strong when P. clarkii experiences
little predation or competition from native predators and has prey that lack efficient defense
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adaptations to it. Its modes of resource acquisition and its capacity to develop new trophic
relationships, coupled with its action as bioturbator, may lead to dramatic direct and indirect
effects on the ecosystem. P. clarkii exerts a greater direct (through consumption) or indirect
(through competition) effect on the other biota, particularly on crayfish species, benthic fish,
molluscs, and macrophytes (Gherardi 2007).
There is an extensive literature showing that North American crayfish species carry a
subclinical infection of the fungus-like Aphanomyces astaci, the aetiological agent of the
crayfish plague.
Because of its omnivorous feeding behaviour, P. clarkii can profoundly modify the
trophic structure of freshwater communities at several levels, often acting as keystone
species. It also displays a wide plasticity in its feeding behavior, switching from
detritivore/scavenger to herbivore/carnivore habits in response to food availability. Even at
low densities, P. clarkii can greatly affect the abundance of some species of submersed
macrophytes and of snails through direct consumption. Reduction of the macrophyte
biomass is also caused by non-consumptive plant clipping and uprooting. Gastropoda are
the taxon most affected and are sometimes eliminated. Procambarus clarkii is however
selective in its choice of molluscs, thin-shelled snails being preferred to thick-shelled species
because they are easier to handle.
Macrobrachium rosenbergii - Macrobrachium rosenbergii has been farmed in dozens of
countries during the past 30 years, but there is little information about its colonization in
natural waters, and there are no reports of any economic damage or environmental impact
related its introduction. However, possible impacts include:
• competition with indigenous species for food, cover or spawning sites.
• introduction of exotic parasites or diseases.
Penaeus indicus and Marsupenaeus (Penaeus) japonicus - Other than competition with
native species for resources, the major problems for this shrimp species are viral infections.
Outbreaks of shrimp viruses may occur due to sudden changes in water quality and poor
pond bottom environment. Common viruses in Marsupenaeus (Penaeus) japonicus include
Yellow Head Disease (YHD), Taura Syndrome (TS) and White Spot Disease (WSD).
Sturgeons - generally are highly attractive species for aquaculture and therefore, were
widely introduced throughout the European continent. Potential adverse effects include
spread of diseases and parasites, competition and/or predation upon native ichthyofauna
and gene introgression. According to the FAO database no adverse effects are reported.
However, escapees or release of fish of aquaculture origin might cause potential negative
effects in wild sturgeon population in terms of genetic variability losses further supported by
easy and common inter-species hybridization, use of hybrids in aquaculture etc.
Unfortunately, no relevant information exists or has been collected in this field and genetic
and accurate potential impact assessment studies should be of interest in future sturgeon
conservation research. Several species of the Sturgeon group are included with separate
fact sheets (Acipenser gueldenstaedti, A. nudiventris, A. stellatus, A. sturio and Huso huso).
Argyrosomus regius - The main impact of farming meagre will be similar to most
aquaculture units, potential pollution and disease transfer, because of the intensity of its
production. There are few data regarding diseases of this species, but there have been
cases of parasitism. The other potential problem is escapes from cages, but this is not
considered a major problem because meagre is indigenous to the Mediterranean basin.
Perhaps the biggest problem will be genetic interactions because juvenile production has
only been established in one farm location, leading to potential inbreeding effects.
Hypophthalmichthys (Aristichtys) nobilis - For the majority of bighead carp introductions,
no records of impacts exist. Bighead carp are often stocked together with silver carp to
control phytoplankton and improve water quality. However, the data has been conflicting. In
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some studies bighead carp increased algal density in ponds whereas in others no difference
was recorded. Bighead carp may reduce blue-green algae blooms. Competition for food
resources between Hypophthalmichthys and other planktivorous fishes has been
documented in polyculture conditions. Competition with native fishes that rely on plankton as
a food source is suggested.
Carassius auratus - The goldfish can pose a high risk to both still and running waters,
although ponds appear to be at the greatest risk of impacts. The species can reproduce in its
second year of life with repeated spawning with a vegetative season, which allows the
species, within a short period of time, to invade small water bodies as well as water courses.
Consequences for native species include genetic contamination through hybridization and for
the recipient ecosystems the impacts include increased turbidity. The risk to introduce exotic
parasites or diseases remains.
Clarias gariepinus - The species is large and highly predatory, thus posing serious potential
to impact on the native fish fauna. Hybrid catfish fry are susceptible to certain pathogens,
particularly Protozoa, Monogenea, immature Digenea (metacercaria) on the gills, and
bacteria. Fish farmers face an economic loss, although some disease problems may be
associated with inadequate farm management practices. Another impact of the farming of C.
gariepiunus is the effect of fish-farm waste, including feed and faecal matter, on the
surrounding ecosystem.
Coregonus peled - In Belgium the reservoir lakes seem to meet the habitat requirements of
C. peled in terms of growth capacities and diet composition. On the other hand, the
conditions necessary for the natural reproduction of these two species do not seem to be
totally fulfilled. In Finnish reservoir lakes the reproduction of Peled has in some years been
successful resulting strong year classes. According to Swedish authorities a weak population
of Coregonus peled in lake Storvindeln in northern Sweden is threatened due to competition
with indigenous species. No reports of new species-specific diseases or special sensitivity to
existing diseases are available. Despite abundant introductions of Coregonus peled to the
western Europe no clear adverse ecological or genetic effects are reported. The species
seems to be a weak competitor in its new habitat.
Ictalurus punctatus - There is very little information on which to make an assessment of the
likely impact of this species under European conditions. Possible impacts on local fish
populations and the aquatic environment might include:
• competition with indigenous fish for food, cover or spawning sites.
• the introduction of exotic parasites or diseases.
• direct predation on other fish.
• adverse effects on the environment (e.g. effects on community structure).
Lates calcarifer - A potential impact associated with the culture of fish in open systems
(cages or ponds draining into water sheds) is the risk of introduction of a disease causing
organism to wild barramundi or sympatric species. The FAO have identified numerous
pathogenic organisms of Barramundi (2 viral, 10 bacterial, 9 protozoan, with 6 others
comprising lice, fungi and trematodes). The risk of transfer of disease causing organisms is
reduced with the use of closed aquaculture systems assuming adequate treatment of effluent
(e.g. ozonation) is carried out and that intermediate hosts (e.g. birds, snails) are excluded
from the culture system. However, the risk of disease within the culture system might be
exacerbated within closed systems.
Mylopharyngdodon piceus - For the majority of cases no information exists or has been
collected about the impacts introducing of black carp, where impacts have been reported
these are both adverse and beneficial. The principle adverse effects relate to spread of
diseases and pathogens, and potential competition with indigenous fauna. The following
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diseases and pathogens have been reported from black carp: Grass Carp Hemorrhagic
Disease Reovirus Viral diseases: high mortality 30 – 60 % and Enteritis (Bacterial
infection) Bacterial diseases with Aeromonas punctata – affect the black carp and grass
carp.
Oncorhynchus kisutch - There is relatively little information upon which to make an
assessment of the likely impacts of this species under European conditions. The occasional
specimen is caught in coastal fisheries but the origin is unknown and the impact
unmeasured. Possible impacts on local fish populations and the aquatic environment could
include:
• direct predation.
• introduction of exotic parasites or diseases.
• hybridisation with native salmonids.
Oreochromis niloticu - Generally, there is relatively little information on which to make an
assessment of the likely impacts of this species under European conditions, but O. niloticus
has been widely classified as a pest where introduced. In semi-tropical and tropical climates
the species has established self-maintaining populations in a variety of habitats, and has
proved difficult to eradicate. Possible impacts on local fish populations and the aquatic
environment may include:
• direct predation.
• hybridisation with native species.
• adverse effects on the environment through habitat destruction (vegetation removal).
Polyodon spathula - There is very little information on which to make an assessment of the
likely impact of these species under European conditions. Possible impacts on local fish
populations and the aquatic environment might include:
• competition with indigenous fish for food cover or spawning sites;
• the introduction of new parasites or exotic diseases;
• adverse effects on the environment through habitat degradation (e.g. effects on benthos,
water turbidity changes due to feeding activity).
Rachycentron canadum - Cobia are susceptible to many viruses, bacteria, and parasites
that commonly afflict other warm water marine species. Managing disease and parasite
issues has been identified as a major challenge with regard to cobia culture.
Salvelinus fontinalis - For the majority of cases no information exists or has been collected
about the impacts introducing brook trout; where impacts have been reported these are both
adverse and beneficial. The main benefits are derived from aquaculture production and
improved sport angling experience, both of which generate income and create employment,
albeit on a local scale. The principle adverse effects relate to spread of diseases and
pathogens, and potential predation and competition with indigenous fauna. Four diseases or
pathogens have been reported from brook trout: whirling disease, enteric redmouth disease,
Hysterothylacium infection and Camallanus infection. Whirling disease is a parasitic infection
caused by Myxobolus cerebralis. It affects juvenile salmonids and causes neurological
damage and skeletal deformation. Brook trout and rainbow trout are the most heavily
affected by this pathogen. This pathogen can be found in much of the brook trout range and
therefore may causes adverse effects to both wild and cultured salmonids in these areas.
Enteric redmouth disease is caused by the bacteria Yersinia ruckeri, which causes
haemorrhaging to the skin, eyes, gill filaments, mouth and internal organs. Enteric redmouth
disease affects a large number of different species as well as salmonids. These may include
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carp, burbot, catfish, eels, minnows, sole, sturgeon, turbot and whitefish. This means that the
introduction of fish carrying this disease may have a huge detrimental ecological impact on
local fish populations. Hysterothylacium infection is caused by a parasitic nematode
Hysterothylacium patagonense. This infection is mainly seen in Patagonia and Argentina. It
infects the digestive tracts of introduced species of fish including brook trout, and brown trout
and probably originates from temperate bass. Camallanus infection is also a parasitic
infection caused by a nematode. This infection affects the stomach, and also mainly affects
trout species.
Some evidence exists for increased predation pressure infauna and epifauna in river
systems where brook trout has been introduced, but these studies are inconclusive. Similarly
there is evidence that brook trout compete with other salmonids where they coexist, although
brook trout are not always the dominant species, and this may explain why the species has
not successfully established in some countries / rivers.
Salvelinus namaycush - Lake trout have been introduced into Swedish lakes since 1959,
and no harm to the native fish populations has been demonstrated. Similarly, with the
exception of predation on whitefish, no interactions between lake trout and native species
have been recorded in the alpine lakes of Switzerland. Predator pressures exerted by lake
trout are, however, believed to have prevented stocked brook trout (Salvelinus fontinalis)
from establishing a self-sustaining population in Castle Lake, California. There is relatively
little information upon which to make an assessment of the likely impacts of this species
under European conditions. Possible impacts on local fish populations and the aquatic
environment could include:
• direct predation (e.g. on whitefish).
• hybridisation with native salmonids.
Sander lucioperca - The introduction of pikeperch has created important commercial and
recreational fisheries, especially in rural areas, but can have severe impacts on local, native
fish populations. Pikeperch can also lead to substantial declines in prey stocks. After
introduction to a water body, pikeperch often go through a population explosion, before
stabilising at a lower level as a balance is established. That adult zander consume their own
young may be an important regulatory mechanism. Possible impacts on local fish
populations and the aquatic environment include:
• direct predation – Pikeperch consume many species of fish.
• the introduction of exotic parasites or diseases. For example, a new nematode,
Lucionema balatonense, has been described from the swimbladder of pikeperch from
Lake Balaton.
Sciaenops ocellatus - This fish species is known as potentially infected with Viral nervous
necrosis, Enteromyxosis (myxidiosis), Lymphocystis, Crustacean ectoparasites (sea/fish
lice), Vibriosis (systemic bacterial infection), Systemic bacterial infection, Amyloodiniosis
(marine velvet disease), Cryptocaryonosis (marine white spot disease).
Silurus glanis - There is relatively little information on which to make an assessment of the
likely impacts of European catfish under UK conditions. Possible impacts on local fish
• direct predation on other fish may cause impacts on native species.
• the introduction of exotic parasites or diseases (has been known to carry the viral disease
SVC).
• The species is a veracious predator of fish, that can take amphibians and crustaceans,
so may have adverse effects on the environment (e.g. effects on community structure).
Deliverable 2.5
10
Hypophthalmichthys molitrix - Silver carp are the fourth most often introduced fish species
in the world. Impact appears to be independent of whether a population has become
established or not at any given location. Both beneficial effects and adverse impacts have
occurred following introduction for the purpose of phytoplankton control and aquaculture. All
associated socio-economic impacts have been recorded as beneficial. The effectiveness of
using silver carp as a biological control agent, mainly for phytoplankton, remains
controversial. There is evidence to suggest carp effectively reduce cyanobacteria, however,
this process is not fully understood and results have been varied. Competition for food
resources between Hypophthalmichthys and other planktivorous fishes has also been
documented in polyculture conditions. However, it was concluded that based on the
probability and consequences of establishment, silver carp pose a potentially high or an
unacceptable risk within the US.
2.3
Decisions on inclusion in Annex IV
Conclusions of the expert workshops held in Brussels in November 2007 and December
2008 are provided in Table 3. The following species were recommended for inclusion on
Annex IV based on information provided by the fact sheets and the set of agreed criteria:
Sander lucioperca;
Coregonus peled;
All proposed sturgeon species:
Acipense baeri;
A. stellatus;
A. gueldenstaedtii;
A. ruthenus;
A. nudiventris;
A. Sturio;
Huso huso;
Salvelinus namaycush;
Silurus glanis;
Clarias gariepinus;
Carassius auratus;
Ictalurus punctatus.
The experts recommended not to adding the following species to Annex IV:
Argyrosomus regius;
Oreochromis niloticus;
Hucho hucho;
Oncorhynchus kisutch;
Mylopharyngodon piceus;
Polyodon spathula;
Pacifastacus leniusculus;
Astacus leptodactylus;
Penaeus japonicus.
With reference to the candidate species requested by France only for the French overseas
departments the following species wee added to a separate part of Annex IV which would
apply only for those territories:
Oreochromis niloticus;
Oreochromis mossambicus;
Sciaenops ocellatus;
(Macrobrachium rosenbergii.
Deliverable 2.5
11
The experts recommended not to adding the following species requested by France only for
the French overseas departments to the above mentioned separate part of Annex IV which
would apply only for those territories:
Rachycentrum canadum;
Lates calcarifer.
Table 3. Species characteristics in light of suitability to be listed in Annex IV of Council Regulation
(EC) No 708/2007
Species
Mollusca
Crassostrea gigas
Crustacea
Procambarus clarkii
Macrobrachium
rosenbergii
Penaeus indicus
Deliverable 2.5
Recommendations for Annex IV of Council Regulation (EC) No
708/2007
A gradual expansion process of Crassostrea gigas has been observed
since its introduction in Europe for aquaculture purposes. The species is
in commercial practice since several decades. Recommendation:
Already included in Annex IV.
Considered as an exotic species and showing an expanding pattern in
several countries, Japanese carpet shell can represent a threat for local
biodiversity. Natural hybridization has been reported between the native
European species Ruditapes decussatus and the exotic R.
philippinarum. Ruditapes philippinarum has become a recent candidate
for polyculture. Clams have been cultured with marine shrimp; in
fertilized seawater ponds with red tilapia; combined with shrimps and
European seabass and gilthead seabream; as well as in the drainage
canals of shrimp ponds.
Rotational culture of R. philippinarum has also been carried out with
Porphyra culture. Polyculture has proved feasible and is a way of
limiting the environmental impacts of aquaculture. Recommendation:
Although evidence that the species impacts on wild crayfish populations
is limited, there is sufficient to indicate that impact can be severe
leading to extirpation of local species.
Recommendation: Like all crayfish species it should be excluded
from Annex IV.
Although the species has been used in aquaculture for more than 30
years, there are considerable impacts on native crayfish species where
it has been introduced, through competition, predation and particularly
the devastating effect of the crayfish plague (Aphanomyces astaci). The
impact can be severe leading to extirpation of local species.
from Annex IV.
years, there are considerable impacts on native crayfish species where
it has been introduced, through competition, predation and disruption of
the ecosystem, leading to extirpation of local species.
from Annex IV.
years, there is no evidence that the species impacts on wild populations
there is a risk of epibionts and spread of disease. Escapees could act
as carriers and contaminate wild life. In the absence of any definitive
evidence the precautionary principle should be adopted.
from Annex IV.
The Indian white prawn does not fulfil the criteria set out in Article 24(2),
i.e. it has been used in aquaculture for a long time in certain parts of the
Community with no adverse effects, and introductions took place
12
Marsupenaeus japonicus
Fishes
Sturgeons
Argyrosomus regius
Hypophthalmichthys
nobilis
Carassius auratus
Clarias gariepinus
Coregonus peled
Ictalurus punctatus
Lates calcarifer
Deliverable 2.5
without the coincident movement of potentially harmful non- target
species. Production is marginal.
Recommendation: exclude from Annex IV.
years, there is evidence that the species impacts on wild fish
populations there is a risk of epibionts and spread of disease. Escapees
could act as carrier and contaminate wild life. In the absence of any
definitive evidence the precautionary principle should be adopted.
from Annex IV.
It was considered that all the species could be treated in the same way.
Some of these species are native in certain parts of Europe and their
introduction in other parts has been carried out for many years without
important adverse effects in Poland. There is a risk of hybridisation with
wild populations but hybridisation also occurs in the wild.
Recommendation: Include all species in Annex IV.
There is only limited aquaculture production in France, Italy and Spain,
but since the species is indigenous to these regions there seems little
reason why the species should be considered in Annex IV. The issue
here is whether the species will be moved to new regions in the EU for
production. Recommendation: exclude from Annex IV.
The species has been used in aquaculture for more than 50 years.
However, potential impacts include circumstantial evidence linking the
introduction of bighead carp to changes in native fish community. This
species is not known for hosting specific diseases or parasites with the
possible exception of the Asian tapeworm. The risk associated with this
species introduction in Europe is considered low. Recommendation:
years, there are no notable effects on the aquaculture sector, but
environmental impacts are known. Although production is not large, the
species is reared for the aquarium and garden pond trade, and if this is
not carried out in a controlled manner could lead to further spread of the
species. It is, however, already widespread within Member States.
Recommendation: include in Annex IV.
years, there are no notable effects largely because it is confined to
indoor recirculation systems, but escapes or releases of the species
could be problematic in southern, Mediterranean climates.
In spite of abundant introductions of Coregonus peled to the western
Europe no clear adverse ecological or genetic effects are reported. The
species seems to be a weak competitor in its new habitats.
Channel catfish is nominated for inclusion in the Annex IV presumably
because it has the capacity to be an important species in aquaculture
production, demonstrated by the large production in the USA and China.
However, production in Europe is only modest and this has only been
developed in the past 15 years. Although production is not large the
species is also reared for stocking and if this is not carried out in a
controlled manner could lead to further spread of the species. It is,
however, already widespread within Member States.
Barramundi is nominated for inclusion in the Annex IV presumably
because it has the capacity to be an important species in aquaculture
production, demonstrated by the large production in Asian Pacific
region. There is only limited aquaculture production in French Polynesia
in the past 10 years. There are no evaluations of the impact but the
species has not been released as yet into Europe. Given the uncertainty
13
Mylopharyngdodon piceus
Oncorhynchus kisutch
Polyodon spathula
Rachycentron canadum
Sander lucioperca
Sciaenops ocellatus
Silurus glanis
Deliverable 2.5
and lack of aquaculture production in Europe, it is not recommended
that the species is included in the Annex IV list for introduction into
Europe but is restricted to French Overseas Territories.
The principle adverse effects relate to spread of diseases and
pathogens, and potential competition with indigenous fauna.. Its trade is
restricted in Germany due to several countries reported adverse
ecological impact after introduction. Recommendation: exclude from
Annex IV.
years, there are no notable effects on the aquaculture sector. There has
been no notable production in Europe since the mid 1990s and there is
no legacy of aquaculture production. Although there is no evidence that
the species impacts on wild fish populations, the species compete with
indigenous salmon for food and spawning sites, and there is a risk of
hybridization with native species. Recommendation: exclude from
Annex IV.
It is nominated for inclusion in the Annex IV list of species foreseen by
Article 2(5) presumably because it is a very successful aquaculture
species worldwide, and has been used in aquaculture for more than 30
years with no notable effects. Production in Europe is low, with culture
currently restricted to indoor recirculation systems in Northern Europe,
but escapes or releases of the species could be problematic in
southern, Mediterranean climates. The nomination was for French
Overseas Territories only. Recommendation: include in Annex IV for
DOM countries.
The species has not been used in aquaculture for more than 30 years in
Europe. It is presumably being considered for inclusion in Annex IV
because of its angling qualities or for caviar production.
France requested this species be included in Annex IV but only for the
French overseas departments (DOM). The species does not comply
with the criteria since the farming of this species at commercial scale is
very recent in those territories. Recommendation: excluded from
Annex IV for DOM countries
Brook trout is included in the Annex IV because it has been used in
aquaculture for more than 30 years with no notable impacts, although
some disease issues were noted. Recommendation: Already
included in Annex IV.
Lake trout is nominated for inclusion in the Annex IV presumably
because has been extensively stocked for fisheries throughout Europe
with no notable effects. Although production is not large the species is
reared for stocking and if this is not carried out in a controlled manner it
could lead to further spread of the species. Recommendation: include
in Annex IV.
Pikeperch is nominated for inclusion in the Annex IV presumably
because it has been used in aquaculture for more than 30 years with no
notable effects. Although production is not large the species is reared
for stocking and if this is not carried out in a controlled manner could
lead to further spread of the species. Where introduced into open water
the species has impacted on species diversity and population structure.
It is, however, already widespread within Member States.
This is a relatively new species in aquaculture (10 years). Frequent
sampling and observation of stock for diseases and/or parasites should
be exercised, and sick fish should timely be removed.
Recommendation: include in Annex IV for DOM countries.
The European catfish is nominated for inclusion in the Annex IV
presumably because of its increasing importance in aquaculture
production. However, production in Europe is only modest compared
14
Hypophthalmichthys
molitrix
Deliverable 2.5
with capture fishery production. Although production is low the species
is also reared for stocking and if this is not carried out in a controlled
manner could lead to further spread of the species. It is, however,
already widespread within Member States and indigenous to eastern
Europe,
mainly
countries,
associated
with
the
Danube.
years, it remains the second most important aquatic species in the world
in terms of aquaculture production. Impacts include circumstantial
evidence linking the introduction of silver carp to changes in native fish
community. This species is not known for hosting specific diseases or
parasites with the exception of the Asian tape worm. In the light of the
empirical evidence, the risk associated with this species introduction in
Europe is low, and the species should remain in Annex IV.
Recommendation: Already included in Annex IV.
15
3
ALIEN SPECIES FACT SHEETS
Deliverable 2.5
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ALIEN SPECIES FACT SHEET
Species name:Pacific oyster
Japanese oyster
Scientific name: Crassostrea gigas (Thunberg, 1793)
Family Name: Ostreidae
Diagnostic Features
C. gigas is a bivalve, epifaunal, suspension/filter feeder that cements itself to rocks and other
hard substrata and feeds primarily on phytoplankton and protists. The Pacific oyster shell is
extremely variable and irregular in shape. Its shape depends on the type of bottom on which
it is grown, as well as the degree of crowding. The external surface may be either smooth or
highly fluted. The colour is brown or purple but mainly grey. The upper flat valve is smaller
than the lower cupped valve. The interior of the shell is normally pure white with a smooth
polished surface. The oyster flesh is covered by a tegument, the mantle involved in the
process of shell calcification. The free space between the two lobes of the mantle is the
pallial cavity, divided by the gills into an inhalant and exhalant part where seawater
circulation occurs (without siphons). Gills act as a filter to retain particles and also oxygen for
the respiration process (Goulletquer et al., 2004). The mouth, surrounded by the labial palps
is near the hinge, whereas the anus is just above the adductor muscle. During the
reproductive activity, the gonadal mass is largely diffuse within the body flesh, and reach up
to 70% of the total dry meat weigh for adults.
Geographic distribution
Originating from the north eastern Asia, C. gigas is endemic to Japan, but has been
introduced and translocated, mainly for aquaculture purpose, into a number of countries,
almost worldwide (Ruesink et al. 2005). In North America, the species can be found from
Southeast Alaska to Baja California, while in European waters the species is cultured from
Norway to Portugal as well as in Mediterranean Sea. C. gigas was introduced into Europe in
the beginning of the 1920’s for marketing and in the 1960’s for aquaculture purposes: in
1965, in UK from North America (Couzens, 2006), in 1964 in the Netherlands from British
Columbia; in 1965 in France from California (USA); in 1971 from a Scottish hatchery in
Germany (Drinkwaard 1999). Biological characteristics make it suitable for a wide range of
environmental conditions, although it is usually found in coastal and estuarine areas within its
natural range.
Deliverable 2.5
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Figure 2. Crassostrea gigas distribution in Europe (from D. Minchin, S. Gollash, B. Galil, EU
project DAISIE)
Habitat and Biology
C. gigas prefers firm bottoms, and is usually attached to rocks, debris or other oyster shells
at depths of between 5 and 40 m. However, they can also be found on mud or mud-sand
bottoms.
Pacific oysters are protandrous hermaphrodites. They change sex, but their timing is erratic
and seasonal. Spawning depends on a rise in water temperatures above eighteen degrees
Celsius. When spawning does occur, it occurs primarily in July and August; eggs (50-100
millions in single spawning) and larvae are planktonic distributed throughout the water
column in estuarine waters. Later stage larvae settle out of the water column and crawl on
the bottom searching for suitable habitat before settling. Juveniles and adults are sedentary
and are found in lower intertidal areas of estuaries.
Diseases
Although C. gigas has shown a large tolerance to diseases agents, explaining its worldwide
production success, several diseases and syndromes have been described. The ‘summer
mortality’ syndrome has been studied worldwide and seems correlated with high seawater
temperatures and the reproductive activity (Goulletquer et al. 1998). Although not totally
understood, this syndrom is likely related to combined factors and highly complex
interactions between environmental conditions – health status and opportunistic pathogens.
Herpes like virus infections are caused by virus presenting similar features, cellular locations
and size characteristic of virions from the Herpesviridae family (Renault et al., 1994). An
oyster velar virus (OVVD) was reported in hatcheries in Washington State (USA) during the
1980s’ affecting larvae greater than 150µm (Elston & Wilkinson 1985).
Deliverable 2.5
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Nocardiosis, an actinomycete bacteria, is usually associated with mortalities during the late
summer and fall. The agent Nocardia crassostreae is distributed in the West coast of North
America from the Strait of Georgia, British Columbia to California and also Japan (Bower et
al. 2005). Vibrios isolates (Vibrio splendidus) have shown a virulence pattern inducing
abnormal mortality rates ((Le Roux et al. 2002).
Mikrocytosis (Denman Island Disease) is due to a small (2-3µm) intracellular protistan
parasite of unknown taxonomic affiliation. First reported in 1960, Mikrocytos mackini is
observed from the west coast of Canada, and likely ubiquitous throughout the Strait of
Georgia and other specific localities around Vancouver Island (Hervio et al. 1993). It was
never detected in Europe.
Due to its life in open waters and a limited immune system, no curative measure is available
for C. gigas diseases, and prevention, adapting management practices remain the option to
limit impacts. In the mid-term, genetic research programs aim to domesticate and develop
selected disease tolerant strains.
Shellfish production
Oyster fisheries have shown poor sustainability. Pacific cupped oyster capture fisheries were
never relevant, with a production of only a few tonnes / year.
Figure 2. Global capture production for Crassostrea gigas (FAO Fisheries statistic)
In 2002, C. gigas aquaculture has reached a 4 216 300 metric tons record high, representing
97.7% of the total oyster culture production in the world (FAO, 2004). European production
ranges around 120 000 tonnes/year with France as a major producer following by Ireland,
Holland, United Kingdom and Spain.
Deliverable 2.5
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Figure 3. Global aquaculture production for Crassostrea gigas (FAO Fisheries statistic)
Impacts of introduction
C. gigas settles in dense aggregations in the intertidal zone, resulting in the limitation of food
and space available for other species. Introductions in sensitive environment have been
numerous. In several countries, uncontrolled natural reproduction led to a significant species
expansion and natural breeding stocks (Cognie et al. 2006). Positive and negative effects
have resulted from habitat changes through reef building capacity :
The potential
environmental impacts related to C. gigas introduction are: 1. displacement of native species
where C. gigas develops breeding populations and became an invasive species in several
countries (New Zealand, Australia), competing for food and space by building massive oyster
beds through its natural spat settlement and recruitment; 2. Benthic-pelagic interactions and
likely food web modifications; 3. Habitat change; 4. Hydridization with local oyster species; 5.
Transfer of parasites, diseases and pest species concomitant to oyster transfer (Occhipinti
Ambrogi, 2001). It is acknowledged that the macrophyte algae Sargassum muticum was
introduced concomitantly to oyster spat in European waters.
Two comments should be emphasized:
• earlier to the massive C. gigas massive introduction, a local strain Crassostrea
angulata was thriving until a viral disease decimated the population along the
European coastline. Based on larval shell morphology, experimental hybridization,
and electrophoretic studies of enzyme polymorphism, several authors have considered
these two species as being synonymous. However, several genetic studies based on
mitochondrial DNA and microsatellites data, as well as their contrasted behavior
against the iridovirus responsible for the “gill disease”, are providing evidences that the
two taxa can be considered genetically distinct although closely related (see review in
Batista et al., 2006).
• the massive C. gigas introduction into the natural environment was carried out using
spat and adult oysters with limited biosecurity practices, and without quarantine
procedures. This resulted in associated species introduction leading to, by way of
example, in local algal species displacement due to the algae invasive pattern (Wolff
and Reise, 2002).
Moreover, shell borers such as Polydora sp. are commensal to oysters and can be
transferred concomitantly, then colonizing other shellfish species (Leppäkoski et al., 2002).
Deliverable 2.5
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Main issues
A gradual expansion process of Crassostrea gigas has been observed since its introduction
in Europe for aquaculture purposes. It seems to be related to the climate change: good
recruitment corresponded with years of extended period of high summer temperature
(Diederich et al. 2006).
No efficient options exist for management to reduce or even stop the spread of the Pacific
oyster (NIMPIS, 2002)
References
Batista F., Leitao A., Huvet A., Lapègue S., Heurtebise S., Boudry P., 2006. The taxonomic status and
st
origin of the Portuguese oyster, Crassostrea angulata (Lamarck, 1819). The 1 International
Oyster Symposium Proceedings, Oyster Research Institute News 18, 2006.10: 3-10.
Bower SM, Goh B, Meyer GR, Carnegie RB, Gee A. (2005) Epizootiology and detection of nocardiosis
in oysters, Vol. Diseases in Asian aquaculture 5: proceedings of the fifth Symposium on
Diseases in Asian Aquaculture, 24-28 November 2002, Queensland, Australia. pp. 249-262.
Cognie B, Haure J, Barille L (2006) Spatial distribution in a temperate coastal ecosystem of the wild
stock of the farmed oyster Crassostrea gigas (Thunberg). Aquaculture [Aquaculture]. 259: 1-4.
Couzens G. (2006). The distribution and abundance of the non-native Pacific oyster, Crassostrea
gigas, in Devon - a result of climate change? Shellfish News 22, pp 5-7.
Diederich S, Thieltges DW, Strasser M (2006) Wadden Sea mussel beds invaded by oysters and
slipper limpets: Competition or climate control? Helgoland marine research [Helgol. Mar.
Res.]. Vol. 60:no. 2.
Drinkwaard AC (1999) Introductions and developments of oysters in the North Sea area: A review.
Helgolaender Meeresuntersuchungen [Helgol. Meeresunters.]. 52:no. 3-4.
Elston RA, Wilkinson MT (1985) Pathology, management and diagnosis of oyster velar virus disease
(OVVD). Aquaculture. 48:no. 3-4.
FAO (2004). The state of world fisheries and aquaculture. FAO Fisheries department,152 pages.
FAO (2008) http://www.fao.org/fishery/culturedspecies/Crassostrea_gigas
Goulletquer P, Soletchnik P, Le Moine O, Razet D, Geairon P, Faury N, Taillade S (1998) Summer
mortality of the Pacific cupped oyster Crassostrea gigas in the Bay of Marennes-Oleron
(France), Vol. ICES, Copenhagen (Denmark). 20 pp. 1
Goulletquer P., M. Wolowicz, A. Latala, C. Brown, S. Cragg, 2004. Application of a micro respirometric
volumetric method to respiratory measurements of larvae of the Pacific oyster Crassostrea
gigas. Aquat. Liv. res., 17:195-200.
Hervio D, Bower SM, Meyer GR (1993) Detection, isolation, and host specificity of Mikrocytos mackini,
the cause of Denman Island disease in Pacific oysters Crassostrea gigas. Journal of Shellfish
Research [J. SHELLFISH RES.]. Vol. 12:no. 1.
Le Roux F, Gay M, Lambert C, Waechter M, Poubalanne S, Chollet B, Nicolas JL, Berthe F (2002)
Comparative analysis of Vibrio splendidus related strains isolated during Crassostrea gigas
mortality events. Aquatic Living Resources [Aquat. Living Resour./Ressour. Vivantes Aquat.].
Vol. 15:no. 4.
Leppakoski E, Gollasch S, Olenin S (2002) Alien Species in European waters, Vol. Invasive Aquatic
Species of Europe: Distribution, Impacts and Management. pp. 1-6.
NIMPIS (2002) http://www.marine.csiro.au/crimp/nimpis/ read 15/01/2008
Occhipinti Ambrogi A., (2001). Transfer of marine organisms: a challenge to the conservation of
coastal biocenoses. Aquatic Conserv.: Mar. Freshw. Ecosyst. 11: 243-251.
Renault, T., (1996). Appearance and spread of diseases among bivalve molluscs in the northern
hemisphere in relation to international trade. Rev. Sci. Tech. Off. Int. Epiz. 15 (2), 551-561.
Ruesink JL, Lenihan HS, Trimble AC, Heiman KW, Micheli F, Byers JE, Kay MC (2005) Introduction of
Non-Native Oysters: Ecosystem Effects and Restoration Implications. Annual Review of
Ecology:Evolution and Systematics [Annu. Rev. Ecol.
Wolff WJ, Reise K (2002) Oyster imports as a vector for the introduction of alien species into northern
and western European coastal waters, Vol. Invasive Aquatic Species of Europe: Distribution,
Impacts and Management. pp. 193-205.
Deliverable 2.5
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Species name:Japanese carpet shell
Scientific name: Ruditapes philippinarum
Adams & Reeve (1850)
Family Name: Veneridae
Biological features
Shell solid, equivalve; inequilateral, beaks in the anterior half; somewhat broadly oval in
outline. Ligament inset, not concealed, a thick brown elliptical arched body extending almost
half-way back to the posterior margin. Lunule elongate heart-shaped, clear though not
particulary well defined, with light and dark brown fine radiating ridges. Escutcheon reduced
to a mere border of the posterior region of the ligament. Sculpture of radiating ribs and
concentric grooves, the latter becoming particulary sharp over the anterior and posterior
parts of the shell, making the surface pronunced decussate. Growth stages clear. Three
cardinal teeth in each valve; centre tooth in left valve and centre and posterior in right, bifid.
No lateral teeth. Pallial sinus relatively deep though not extending beyond the centre of the
shell; it leaves a wedge-shaped space between its lower limb and the pallial line. Margin
smooth. Extremely variable in colour and pattern, white, yellow or light brown, sometimes
with rays, steaks, blotches or zig-zags of a darker brown, slightly polished; inside of shell
polished white with an orange tint, sometimes with purple over a wide area below the
umbones.
Historical background
The Japanese carpet shell (also known as the small-neck or Manila clam) is a subtropical to
low boreal species of the western Pacific and is distributed in temperate areas in Europe.
Wild populations are found in the Philippines, South and East China Seas, Yellow Sea, Sea
of Japan, Sea of Okhotsk, and around Southern Kuril Islands. Its culture was initiated in
those areas from the initial traditional fishing activities by the collection of wild seeds.
Of considerable commercial value, Japanese carpet shells have been introduced to several
parts of the world, where they have become permanently established. Accidentally
introduced during the 1930s to the Pacific coast of North America along with Pacific cupped
oyster seed, Japanese carpet shells have spread to colonize the coast from California to
British Columbia. Besides public fisheries, hatchery production has facilitated Japanese
carpet shell culture along the Pacific coastline. Japanese carpet shells were also transferred
from Japan to Hawaiian waters early in the 20th century, where wild populations now occur.
Deliverable 2.5
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Overfishing and irregular yields of the native (European) grooved carpet shell, Ruditapes
decussatus, led to imports of R. philippinarum into European waters. This species was
introduced in 1972 through French hatchery production. Additional imports into the United
Kingdom from Oregon (United States of America) were followed by numerous transfers
within European waters for aquaculture purposes (Portugal, Ireland, Spain, and Italy).
Moreover, aquaculture trials resulted in seed being imported into French Polynesia, the US
Virgin Islands, Norway, Germany, Belgium, Tunisia, Morocco, and Israel. Following the large
aquaculture hatchery based on developments in Europe over the 1980s, natural reproduction
resulted in a geographical expansion of wild populations, particularly in Italy, France, and
Ireland, where Japanese carpet shells have proved to be hardier and faster growing than the
endemic R. decussatus. Consequently, R. philippinarum populations are now the major
contributor to clam landings in Europe, and are the focus of intensive public fisheries,
competing with aquaculture products in several rearing areas.
Habitat and biology
The Japanese carpet shell (Ruditapes philippinarum) is native to Japan with a wide
distribution in the Indian and Pacific Oceans from Pakistan to the Russian Federation (Kuril
Islands). It has subsequently been introduced along the North American Pacific coast, the
Hawaiian Isles and, over the last 20 years, along the European coastline from the United
Kingdom to the Mediterranean Basin.
Japanese carpet shells are strictly gonochoric and their gonads are represented by a
diffused tissue closely linked to the digestive system. The period of reproduction varies,
according to the geographical area; spawning usually occurs between 20-25 °C. A period of
sexual rest is observed from late autumn to early winter. Gametogenesis in the wild lasts 2-5
months, followed by the spawning. A second spawning event may occur in the same season,
2-3 months later. The pre-winter recovery phase facilitates energy build up, by filtering
seawater still rich in organic matter and phytoplankton. Temperature and feeding are the two
main parameters affecting gametogenesis, which can be initiated at 8-10 °C and is
accelerated by rising seawater temperature. Its duration decreases from 5 to 2 months
between 14 and 24 °C. Within this temperature range, Japanese carpet shells are ready to
spawn. Although the optimal temperature is between 20 and 22 °C, 12 °C is the minimum
threshold below which this species cannot spawn efficiently. Food availability influences the
amount of gametes produced. Larval development lasts 2 to 4 weeks before spatfall.
Settlement size is between 190 and 235 µm in shell length. Many external factors regulate
spatfall success in the wild, such as temperature, salinity and currents. Larval movement
mainly depends on wind driven and tidal currents. Adding pea gravel and small rocks can
facilitate species recruitment in natural setting areas. The larvae settle by attaching a byssus
to a pebble or piece of shell.
Production statistics
Since 1991, global Japanese carpet shell production has shown a huge expansion, by a
factor of nearly six times. It now represents one of the major cultured species in the world
(2.36 million tonnes in 2002). China is by far the leading producer (97.4 percent in 2002).
Disease factors have impacted production in some other countries, notably in the Republic of
Korea. In the decade 1993–2002, production in that country varied between 10 000 and 19
000 tonnes. Production in Italy, following its introduction, the development of wild
populations, and the consequential increase in seed supply, is the second highest in the
world, at over 41 000 tonnes in 2002. Other countries producing more than 1 000 tonnes in
2002 were the United States of America and France. Extensive production also occurs in
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Japan but is not reported within this specific statistical category, being included within 'clams,
etc. nei'.
Figure 2. Global aquaculture production of Ruditapes philippinarum
In France and the United Kingdom, all cultured clams are sold fresh to local markets and
restaurants. In Italy, clams are sold on the domestic market but large quantities are also
exported to Spain. In Ireland, the low demand prompted the producers to export their fresh
products to France and Spain. Since the supply has been increasing in European waters
from the capture fisheries, Japanese carpet shell prices have inversely decreased.
Presently, all the cultural practices related to the Japanese carpet shell (Manila clam) are
under-control, including hatchery production, and the species has been widely used
worldwide. The biological characteristics of the species favour further developments.
Therefore, the aquaculture production of Ruditapes philippinarum is likely to increase in the
near future, either through expanding acreage or by new introductions into suitable areas
and countries. However, the main factor that has caused production changes in several
countries has been the impact of disease and abnormal environmental conditions. The
'brown ring' bacterial disease has slowed down production in several traditional producing
countries (European Atlantic waters). Besides disease problems, the development of wild
populations following the introduction of this species has induced several changes in
production trends, either by facilitating the seed supply (Italy) or in contrast, by competing
economically with culture (France) then favouring public fisheries. Along the western North
American coast, non-indigenous predators (green crabs) pose a potential risk for commercial
production.
Main issues
Considered as an exotic species and showing an expanding pattern in several countries,
Japanese carpet shell can represent a threat for local biodiversity. Natural hybridization has
been reported between the native European species Ruditapes decussatus and the exotic R.
philippinarum. Similarly to other bivalve filtering species, the extent and scale of impact of the
various biotoxins and the inability to control algal toxins is a major limiting factor for its
culture. Bioaccumulated toxins can cause to long industry closures and sales prohibitions,
therefore impacting the shellfish farming economy.
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Ruditapes philippinarum has become a recent candidate for polyculture. Clams have been
cultured with marine shrimp (Marsupenaeus (Penaeus) japonicus and Fenneropenaeus
(Penaeus) penicillatus); in fertilized seawater ponds with red tilapia (Oreochromis
mossambicus*O. niloticus); combined with shrimps (M. japonicus) and European seabass
(Dicentrarchus labrax) and gilthead seabream (Sparus aurata); as well as in the drainage
canals of shrimp ponds.
Rotational culture of R. philippinarum has also been carried out with Porphyra culture.
Polyculture has proved feasible and is a way of limiting the environmental impacts of
aquaculture.
Responsible aquaculture practices
Epizootic events in shellfish culture have demonstrated the need for preventative measures
to avoid the spread of disease, including :
• Monitoring clam populations for health ;
• Establishing zoning systems to limit the spread of parasites ;
• Using appropriate management practices when transferring or introducing potential
species for aquaculture.
Aquatic Animal Health Code. Although both Perkinsus olseni and Vibrio tapetis are not listed,
any clam transfers should be carried out with great care.
Implementation of the FAO Code of Conduct for responsible fisheries (Article 9 –
Aquaculture development), the ICES Code of Practices for Introduction and Transfer of
Marine Organisms and recommendations for a sustainable aquaculture from the Convention
of Biological Diversity are of particular importance for this species.
Japanese carpet shells have unintentionally colonized coastal areas in several countries
where clam culture has been developed. Therefore, it might be considered as a pest in
specific environmental conditions.
References
Barnabe, G. (ed.). 1994. Aquaculture: biology and ecology of cultured species. Ellis Horwood Series in
Aquaculture and Fisheries Support, Wiley & Sons, Chichester, UK. 403 pp.
Bartley, D.M. 1994. Towards increased implementation of the ICES [International Council for the
Exploration of the Sea]/EIFAC [European Inland Fisheries Advisory Commission] codes of
practice and manual of procedures for consideration of introduction and transfers of marine
and freshwater organisms. 18th Session European Inland Fisheries Advisory Commission 1725 May. Document N° EIFAC/XVIII/94/inf. 18. FAO, Rome, Italy. 3 pp.
Carlton, J.T. 1999. Molluscan invasions in marine and estuarine communities. Malacologia, 41(2):439454.
Choi, K.S., Park, K.I., Lee, K.W. & Matsuoka, K. 2002. Infection intensity, prevalence, and
histopathology of Perkinsus sp. in the Manila clam, Ruditapes philippinarum in Isahaya Bay,
Japan. Journal of Shellfish Research, 21(1):119-125.
ESAV. 1990. Tapes philippinarum: biologia e sperimentazione. Coord. G. Alessandra. Regione
Veneto Ente di Sviluppo Agricolo, Regione Veneto, Italy. 299 pp.
Gosling, E.M. 2003. Bivalve molluscs: biology, ecology and culture. Fishing New Books, Oxford,
England. 443 pp.
Goulletquer, P. 1997. A bibliography of the Manila clam Tapes philippinarum. IFREMER, RIDRV97.02/RA/LA. IFREMER, Tremblade, France.122 pp.
Guo, X., Ford, S. & Zhang, F. 1999. Molluscan aquaculture in China. Journal of Shellfish Research,
18(1):19-31.
ICES. 1995. ICES Code of practice on the introductions and transfers of marine organisms. ICES
Copenhagen, Denmark. 5 pp. (http://www.ices.dk)
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ICES. 2004. Trends in important diseases affecting the culture of fish and molluscs in the ICES area,
1998-2002. Cooperative Research Report, No 265, ICES, Copenhagen, Denmark. 33 pp.
IFREMER. 1988. Dossier: La Palourde, dossier d'élevage [Clam culture: a guide]. Ifremer edit., Paris,
France. 106 pp.
MacKenzie, C.L. Jr., Burnell, V.G. Jr., Rosenfield, A. & Hobart, W.L. (eds.). 1997. The history, present
condition, and future of molluscan fisheries of North and Central America and Europe. US
Dept of Commerce, NOAA Technical Reports 127(1):234 pp; 128(2):217 pp; 129(3):240 pp.
NMFS, Washington DC, USA.
Manzi, J.J. & Castagna, M. (eds.). Clam mariculture in North America. Developments in Aquaculture
and Fisheries Science, 19. Elsevier Press, Amsterdam, Netherlands. 461 pp.
Menzel, W. (ed.). 1990. Estuarine and Marine Bivalve Mollusk Culture. CRC Press, Boca Raton,
Florida, USA. 362 pp.
Turner, G.E. (ed.). 1988. Codes of practice and manual of procedures for consideration of
introductions and transfers of marine and freshwater organisms. EIFAC Occasional Paper No.
23. European Inland Fisheries Advisory Commission (EIFAC), FAO, Rome, Italy, 46
pp.
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ALIEN SPECIES SHEET
Species name: narrow-clawed crayfish, long clawed crayfish,
slender-clawed crayfish, Turkish crayfish,
galician crayfish
Scientific name: Astacus leptodactylus Eschscholtz, 1823
Family name: Astacidae
Notes about systematics
The systematics of Ponto-Caspian crayfish species is in a state of flux. In Western Europe,
papers refer to it as A. leptodactylus, but in some Eastern European countries the species is
called with a variety of names based on subspecies that have been elevated to specific level.
For this reason, A. leptodactylus can be better indicated as a species complex.
B
A
C
Figure 1. Astacus leptodactylus: A) dorsal view; B) Astacus leptodactylus: chela (left); C) pleopods
(right). (Photos by Manfred Pöckl)
Diagnostic features
Morphologically A. leptodactylus is a very plastic species, particularly in the form of the
carapace and chelae, but also colour (Fig. 1). The carapace is relatively thin, varying from
egg-shaped to pear-shaped; the sides and top of both anterior and posterior carapace are
covered with spines and tubercles, which vary in number, density and size; there two pairs of
well-developed post-orbital ridges with one apical spine on each. The borders of the rostrum
are more or less parallel until the shoulder region with or without small spines; the acumen is
long and prominent. Chelae are highly variable in shape with broad to narrow hands and
elongated and relatively narrow fingers with spinous tips; fingers can be straight or more or
less sickle-shaped; the inner side of fixed fingers has numerous small tubercles. The ends of
pleopods 2-4 are pointed, with one or two sub-terminal spines. The colour varies from green
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or grey to dark brown or almost black, the dominant being honey-brown or oil-green; blue
varieties are also known.
Astacus leptodactylus is indigenous to the Ponto-Caspian Basin and the Black, Azov and
Caspian seas, but it has gradually spread to occupy most European countries both naturally
and aided by man; the main vectors have been: deliberate introductions, escapes from fish
markets, and transport via canals. It is now present in 30 European countries (except Spain,
Portugal, Norway and Sweden), as well as Armenia, Georgia, Iran, Asiatic Turkey,
Turkmenistan and Uzbekistan. The origin of one of the common names used in Western
Europe suggests that it was most probably from Galicia that the species was taken for
introduction purposes in the 19th century. It was at this time that the first wave of
introductions of A. leptodactylus took place. Because Galician crayfish were assumed to be
immune to crayfish plague, fishermen tried to use it to replace expurgated A. astacus
populations. It was introduced to waters of western Poland and Germany, Lithuania, Latvia,
and most probably to the Czech Republic and Slovakia. In Belgium, the first evidence of this
species was in 1950. Astacus leptodactylus is assumed to be indigenous in Belarus, Croatia
(where it appears to be extending its distribution naturally in the southwestern part), Moldova,
Romania, Bulgaria, Turkey, Hungary, Serbia, Greece, Bosnia-Herzegovina, Slovakia and
probably also Austria. The second wave of introductions of this species was connected to
crayfish commercial exports from Turkey and Poland in the 1970s and from Turkey in the
1980s. At these times A. leptodactylus was introduced into waters of Denmark, the
Netherlands, Luxembourg, France, Italy, Switzerland, England, and unsuccessfully to Spain.
Its presence in Luxembourg is restricted to a pond and a brook.
Figure 3. Distribution of Astacus leptodactylus populations. (After Souty-Grosset et al. 2006)
Habitat and biology
Astacus leptodactylus inhabits a wide range of environments, from brackish (lagoons,
estuaries) and fresh waters (rivers, canals, reservoirs, lakes, ponds, and swampy areas).
Adults are able to survive salinities of 28°/oo overextended periods and berried females can
survive salinities of 21°/oo whilst incubating their eggs, but eggs only hatch in salinities <
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7°/oo. It is tolerant to low oxygen content, low transparency of water, and increased
temperatures, but is susceptible to pollution. It is also highly susceptible to crayfish plague.
Astacus leptodactylus is a relatively fast growing species with specimens reaching a
total length of 20 cm. The life span is unknown, but the finding of larger specimens suggests
an age greater than five years.
Sexual maturity occurs in the third (2+) or fourth year (3+) of life. The time of mating
depends on location, e.g. in Turkey it takes place during October and November, and in
Switzerland in November-December. In the Caspian Sea mating extends from February to
May. Similarly, the egg laying period depends on the geographical location of the population.
Fecundity varies between populations, e.g. the mean number of ovarian eggs ranges from
210 in Lake Egridir (Turkey) to 528 in the Dnestr River (Ukraine). Survival of eggs and
juveniles varies from 42-53% for egg bearing females of 7.1-8.0 cm TL to 48-91% for
females sized 15.1-16.0 cm TL
Astacus leptodactylus is omnivorous, but prefers zoobenthos, which might make up
to 97% of the biomass of its food in the first year of life in the Caspian Sea. The percentage
of macrozoobenthos in the food of adult crayfish can vary between populations from 27 and
92%. The most important predators of A. leptodoctylus are sturgeon, especially beluga
(Huso huso) in the Caspian Sea, and pike (Esox lucius), catfish (Silurus glanis), eel (Anguilla
anguilla) and perch (Perca fluviatilis). The main terrestrial predators are the otter (Lutra lutra)
and recently the American mink (Mustela vison).
The above features together with its relative high fecundity and fast growth suggest
that A. leptodactylus can be more competitive than other crayfish species when they come in
contact, mostly to A. astacus. There are some reports of extirpation of A. astacus by A.
leptodactylus, particularly in Eastern Europe, although in some cases the two species live in
the same water body, sometimes hybridising. The coexistence of A. leptodactylus with A.
astacus and A. torrentium has been reported in Switzerland and Luxembourg. Observations
have been made in Poland on the extirpation of A. leptodactylus coexisting with Orconectes
limosus for several years.
Fish production
Astacus leptodactylus is popular as a food item in the southern part of European Russia
(estimated consumption: 0.4 kg crayfish/person/year) and the Ukraine. In 1940 in the former
USSR the annual yield of crayfish was 1712 t and in Ukrainian SSR 120 t. In the Ukraine in
1971 the annual yield was approximately 650 tonnes. There is still an abundant and
exploited harvest in the Caspian Sea and in many water bodies and rivers of countries
bordering the Ponto-Caspian basin. It is estimated that the harvest is 70-110 t/yr in the
Astrakhan region and 22 t/yr in the Karelia region. However, pollution seems to have had an
impact on some Russian resources; in the lower Don, its biomass has dropped 17-fold, with
the catches coming to only 23-25 t.
In Turkey large quantities of A. leptodactylus were harvested and exported to
Western Europe until 1986. Due to over-fishing, pollution and crayfish plague, total
production collapsed from 5000 t in 1984 to 200 t in 1991, but the harvest level has now
increased to stabilise between 1600 and 1900 t annually. In England, where A. leptodactylus
was imported in the 1970s and 1980s for fish markets, and which subsequently escaped or
was deliberately introduced into the wild, large stocks have developed, particularly in canals,
reservoirs, lakes and gravel pits around London. Some of the populations are harvested and
supplied to restaurants or exported. Since 1997, Iranian A. leptodactylus have been imported
to Europe (Germany, Austria, France, and Italy).
Several methods for culturing have been developed in the Ukraine, Russia, Turkey,
Bulgaria and France. In Ukraine, the maximum production in outdoor ponds may reach 420
kg/ha. In some regions of Europe breeding for restocking purposes is being carried out (e.g.
Karelia region of Russia and Poland). In Poland the rapid decrease of A. leptodactylus
stocks has resulted in restocking programmes.
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No in-depth studies have been conducted to assess the ecological impacts of Astacus
leptodactylus introductions but it is an invasive species and can form dense populations. Due
to its large size and high fecundity, it may displace other crayfish species in the same waterbody. It has been recorded as displacing A. astacus. In Britain, where A. leptodactylus has
been introduced and is now common in the wild, it has been placed on Schedule 9 of the
Wildlife & Countryside Act, which declares it as a pest. It is not permitted to keep it without a
licence.
Factors likely to influence spread and distribution
•
•
•
•
Ability to tolerate adverse environmental conditions.
Astacus leptodactylus has a high tolerance to saline conditions and may be able to
colonise the estuarine environment as it has done in its home range; it will allow it to
move between freshwater systems through estuaries and potentially around the coast.
Popularity to produce from the wild could result in illegal movements.
Flooding of water bodies could result in dispersal from ponds through rivers.
References
Ackefors H. & Lindqvist O.V. (1994) Cultivation of freshwater crayfish in Europe. In: Huner J.V. (ed.)
Freshwater crayfish aquaculture in North America, Europe, and Australia: Families Astacidae,
Cambaridae and Parastacidae. Food Products Press, New York, pp. 157-204.
Alexandrova E. (1999) Parastacus leptodactylus: cultivation and restoration in Central Russia.
Freshwater Crayfish 12, 563-572.
Arrignon J. (1996) Les écrevisses. Pisciculture Française 123, 1-35.
Baran I. & Soylu E. (1989) Crayfish plague in Turkey. Journal of Fish Diseases 12, 193-197.
Cukerzis J.M. (1968) Interspecific relation between Astacus astacus and Astacus leptodactylus
(Ersch.). Ekologia Polska Seria A 31, 629-636.
Fitzpatrick J. (1996) Eurasian crayfish taxonomy revised – paper review. Crayfish news – IAA
Newsletter 19, 5-7.
Furrer S.C., Cantieni M. & Duvoison N. (1999) Freshly hatched hybrids between Astacus astacus and
Astacus leptodactylus differ in chela shape from purebred offspring. Freshwater Crayfish 12, 9097.
Harlioglu M.M. & Harlioglu A.G. (2005) The harvest of freshwater crayfish Astacus leptodactylus
(Eschscholtz, 1823) in Turkey. Reviews in Fish Biology and Fisheries 14, 415-419.
Köksal G. (1988) Astacus leptodactylus in Europe. In: Holdich D.M., Lowery R.S. (eds) Freshwater
crayfish. Biology, management and exploitation. Croom Helm, London, pp. 365-400.
Laurent P.J. (2003) Astacus leptodactylus Eschscholtz, 1823, serait-elle capable de stopper l’avance
d’Orconectes limosus Rafinesque? L’Astaciculteur de France 74, 8-16.
Machino Y. & Holdich D.M. (2006) Distribution of crayfish in Europe and adjacent countries: updates
and comments. Freshwater Crayfish 15: 292-323.
Skurdal J. & Taugbøl (2002) Astacus. In: Holdich D.M. (ed.) Biology of freshwater crayfish. Blackwell
Science Ltd., Oxford, pp. 467-510.
Souty-Grosset C., Holdich D.M., Noël P.Y., Reynolds J.D. & Haffner P. (eds) (2006) Atlas of Crayfish
in Europe. Muséum national d’Histoire naturelle (Patrimoines naturels, 64), Paris.
Starobogatov Ya.I. (1995) Taxonomy and geographical distribution of crayfishes of Asia and East
Europe (Crustacea, Decapoda, Astacoidea). Arthropoda Selecta 4, 3-25.
Stucki T.P. (1999) Life cycle and life history of Astacus leptodactylus in Chatzensee pond (Zurich) and
Lake Ägeri, Switzerland. Freshwater Crayfish 12, 430-448.
Yildiz H.Y., Köksal G., Benli A.C.K. (2004) Physiological responses of the crayfish Astacus
leptodactylus to saline water. Crustaceana 77, 1271-1276.
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Species name:North American Signal Crayfish
Figure 1. Signal
crayfish (Pacifastacus
leniusculus). Photo
http://www.defra.gov.uk/fish/freshwater/
crayfish.htm
Scientific name: Pacifastacus leniusculus (Dana)
Family Name: Astacidae
Diagnostic features
Pacifastacus leniusculus has features common to all species of freshwater crayfish in as
much as it is divided into three main parts; the head, thorax and abdomen, and can easily be
confused with the noble crayfish (Astacus astacus), only European native freshwater crayfish
species. The signal crayfish can range in colour from bluish-brown to reddish brown with the
underside of the chela (1st claw) bright red. The species can be distinguished from the noble
crayfish, both as juvenile and adult, by the smooth nature of the chelae and the lack of a row
of spines on the shoulders of the carapace behind the cervical groove (Lewis 2002). Adult
signal crayfish also has a distinct white-turquoise patch on the upper side of the chelae at the
junction of the fixed (propodite) and moveable (dactylopodite) fingers (Holdich 1999; Pöckl et
al. 2006). Female specimens can be identified by the presence of oviducts located at the
base of the second pair of walking legs once they have reached maturity (Groves 1985).
They are also identifiable when ‘berried’ by the presence of a mass of black to grey eggs on
the underside of the abdomen. The average length of an adult male from the tip of the
rostrum to the end of the telson is 16 cm, slightly larger than the female at 12 cm (Holdich
2005); weight is typically 60 and 110 g at 50 and 70 mm carapace length. Maximum age of
P. leniusculus is approximately 20 years.
Geographical distribution
Signal crayfish is native to northwest USA and southwest Canada from British Columbia in
the north, central California in the south, and Utah in the east (Lewis 2002). The species has
been present on the European mainland since late 19th Century, when it was believed to
have been discharged along with water ballast from an American cargo ship in 1860 at either
Seligo (Larsen, 1998), or Genoa (Ackefors, 2000) in Southern Italy. It has subsequently been
introduced into Austria, Belgium, Czech Republic, Denmark, England, Finland, France,
Germany, Hungary, Italy, Kaliningrad (Russia), Latvia, Lithuania, Luxembourg, Netherlands,
Poland, Portugal, Scotland, Spain, Sweden, Switzerland and Wales (Holdich 2002; Machino
& Holdich 2005; Souty-Grosset et al. 2006 - Fig. 2) and Japan (Kazuyoskhi et al. 2002).
Wholesale stocking of P. leniusculus in Europe began in Sweden in 1962 (Welcomme 1988)
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as a response to the devastation of its native noble crayfish (Astacus astacus) population as
a result of crayfish plague (Aphanomyces astaci) which first arrived in the country with a
shipment of infected P. leniusculus from Norway in 1907 (Taugbol 2006). The importance of
the crayfish, both in monetary and societal values, drove the initiative to stock natural water
bodies and aquaculture units with P. leniusculus imported from the US. Further introductions
of P. leniusculus to Europe continued throughout the 1960s until the 1980s. Unfortunately,
this crayfish has been carelessly introduced to various countries without considering that it
carries the crayfish plague, and thus causes the eventual extermination of native crayfish.
This was the case both in Great Britain and in Japan.
Figure 2. Distribution of signal crayfish (Pacifastacus leniusculus) in Europe. (After Souty-Grosset et
al. 2006).
Habitat and biology
Pacifastacus leniusculus is a large, hardy cool temperate freshwater crayfish that is found in
a wide range of habitats from small streams to large rivers and natural lakes, including subalpine lakes (Lowery & Holdich 1988; Lewis 2002). Signal crayfish can also survive in
brackish water (Holdich et al. 1997). Pacifastacus leniusculus has the ability to thrive in
almost any waterway that does not have a pH below 6.5; a factor that affects most crayfish
species (Reeve 2004). A lack of calcium in the water inhibits the growth of the animal and
causes it to die through stress. It is tolerant to a wide range of temperatures and will survive
up to 31.1°C and as low as 1°C (Kazuyoshi et al. 2002) and is most active nocturnally
between a temperature range of 14-18°C (Stanton 2004; Bubb et al. 2004). Pacifastacus
leniusculus is very active and migrates up and down rivers, as well as moving overland
around obstacles. However, its rate of colonisation is relatively slow and may only be about 1
km per year.
Pacifastacus leniusculus prefers steep sloping bottoms of caly with a littoral zone of
small to mefium rocks and steep clay banks (Kirjavainen & Westerman 1999). It is
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considered to be a non-burrowing species, but in Europe in constructs burrows under rocks
or in river and lake banks (Guan 1994; Sibley 2000). Their burrows can reach high densities
(up to 14 per metre of river bank) and it can have a serious impact on bank morphology,
causing them to collapse.
Like all crayfish,it is a solitary animal and is omnivorous. Although its diet is mainly
vegetarian it will eat anything from decaying roots and leaves to meat, including crayfish
smaller than themselves(Lewis 2002).
Size at maturity of P. leniusculus is usually 6-9 cm TL (from tip of head to edge of
tail-fan) at an age of 2-3 years, although maturity can occur as early as 1 year. The signal
crayfish has a typical life cycle of a member of the crayfish family Astacidae (Lewis 2002).
Mating and egg laying occurs during autumn, mainly in October. After egg laying, the female
carries the eggs under the tail until hatching; typical egg numbers range from 200 to 400.
Egg incubation time ranges from 166 to 280 days. In natural populations hatching occurs
from late March to the end of July depending on latitude and temperature. The eggs hatch
into miniature crayfish that stay with the mother for three stages (two moults). In the third
stage the juvenile crayfish gradually become more and more independent of the mother,
adopting a solitary life. Estimates of survivorship to age 2 vary from 10-52%, being
dependent on both abiotic and biotic factors. Competition and cannibalism can greatly affect
survival in dense populations.
It is an aggressive competitor and has been responsible for displacing indigenous
crayfish species wherever it has been introduced. In addition, it acts as a vector for the
crayfish plague fungus, Aphanomyces astaci, to which all non-North American crayfish are
susceptible, but to which it is relatively immune. It is a large, relatively fast-growing species
with high fecundity. Consequently, it has proved a good aquacultural species and supports
capture fisheries in the western USA and Europe, particularly in Finland and Sweden.
Production
The growing demand for crayfish for the UK domestic restaurant trade from the mid 1970s
encouraged approximately 250 farms to diversify into their production (Stanton, 2004).
Pacifastacus leniusculus was the most popular of three species introduced for this purpose
because of its fast weight gain (Ackefors 1999). Aquaculture production of signal crayfish
began in 1987, when 2 t were produced in the UK. Production steadily increased to a peak of
15 t in 1990, but has since fallen (1 t in 2005) (Fig. 2). The main producer is the UK, with only
minimal contributions from France and Spain (maxima of 1 t per year). Capture fishery
production, data appear to largely inaccurate FAO statistics suggest capture was
represented entirely by the UK, with between 50 and 100 t harvested each year from 20002003, before the fishery closed in 2004 (Fig. 2), but Ackefors (1998) estimated a total of 355 t
of signal crayfish was produced from capture fisheries in Europe as a whole in 1994. This
level has increased considerably, and in Sweden in 2001 estimated catch was 1200 tonnes.
In recent years, however, levels have fallen for unknown reasons. No capture fishery or
aquaculture production occurs beyond Europe. Following a collapse in the demand for
crayfish in the mid 1980s, precipitated perhaps by the first recorded outbreak of crayfish
plague (A. astaci) at the same time (Guan & Wiles 1997), many ponds were abandoned or
neglected. Although P. leniusculus had already found its way into open waters from as early
as 1976 (Guan & Wiles 1997) through both escaping from captivity and intentional release,
frequency of the species’ discovery in the wild increased rapidly from the late 1980s onwards
(Stanton 2004).
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120
Aquaculture
Capture
100
15
80
10
60
40
Capture (t)
Aquaculture (t)
20
5
20
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
0
1985
0
Year
Figure 2. Trends in the capture fishery and aquaculture production of signal crayfish in Europe.
The disruption caused by P. leniusculus to ecosystems is quite variable. In Europe, P.
leniusculus occupies the same ecological niche as native crayfish species (Taugbol 2006)
and has caused the extirpation of populations of native crayfish populations, particularly the
endangered white-clawed crayfish (Austropotamobius pallipes (Holdich 1999; Hiley 2003).
Pacifastacus leniusculus is an opportunistic polytrophic feeder that may exert significant
grazing pressure on macrophytes, or predation on aquatic insects, snails, benthic fishes and
amphibian larvae, including native crayfish species (Guan & Wiles 1997; Nyström 1999,
2002; Lewis 2002). In flowing rivers the principle disruption is to pre-existing populations of
native crayfish both through predation and loss of habitat, although it is widely held that the
domination of P. leniusculus over native populations is the result of its resistance to A. astaci.
(see below). In closed water systems P. leniusculus is documented as impacting far more
heavily by grazing on flora and fauna that are not replaced as readily as they would be in an
open system (Reeve 2004).
In Europe, P. leniusculus had developed the habit of burrowing into bank sides. This
activity can have a detrimental effect in the form of weakened bank sides that become
increasingly susceptible to erosion. Farmers have also been cited as victims because
livestock are injured when stepping into the burrows and breaking limbs. This is uncommon
behaviour in the species in its native waters, preferring instead to make its home under rocks
on the bottom of a water body (Dukes & Mooney 2004). Pacifastacus leniusculus is also
thought to pose considerable threat to migrating Atlantic salmon as not only is it a keen
devourer of the eggs and fry of this fish, it also competes for the same shelter during the
moulting period when the animal is soft bodied and therefore more vulnerable to predators,
P. leniusculus is an aggressive species that stands up to and attacks potential threats
(Groves 1985). This tendency, coupled with its size, gives the species a distinct advantage
over native crayfish such as A. pallipes which is smaller and shyer than the former.
Pacifastacus leniusculus has the ability to regenerate limbs lost through fight or flight, a
feature held common amongst all freshwater crayfish (Groves 1985).
The main impact of introducing P. leniusculus has been as a vector of the crayfish
plague fungus, Aphanomyces astaci, which has caused large-scale mortalities amongst
indigenous European crayfish populations, particularly in England (Alderman 1997). The
fungus infects its host organism by attaching itself to soft tissues beneath the carapace.
Hyphae are then sent both along the central nerve and into the flesh as well as being sent
out into the water to release further spores. Indigenous European crayfish species have no
Deliverable 2.5
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resistance against this disease and experience total mortality. American crayfish species on
the other hand have co-evolved with the crayfish plague and developed defence systems
making them a natural host for and carrier of this parasitic disease (Unestam 1972, Evans &
Edgerton 2002). Most, if not all, signal crayfish are infected by the crayfish plague. Thus, if a
signal crayfish population is established in a watercourse, the crayfish plague is also
established. For this reason, the spread of signal crayfish is the most serious threat to the
indigenous crayfishes of Europe. The disease has been confirmed in P. leniusculus from
western Hungary, which could have serious implications for indigenous crayfish in the
Danube catchment (Kiszely 2004). Aphanomyces astac is classed by the Global Invasive
Species Programme as being in the top 100 of the world’s worst invaders. This is attributable
to the devastating speed and efficiency with which it can wipe out populations of native
crayfish. The impact is made worse in some cases because stocks of native crayfish affected
by A.astaci are replaced with P. leniusculus, the original source of the infection. Once
present, the free swimming spores infect susceptible species and from there can be passed
on to whole populations. Other causes of the spread of A. astaci are by movement of water,
birds flying from infected waters to clean, the movement of boats along waterways carrying
spores either on their hulls or in bilges and by fishing gear such as nets and waders being
used in infected waters and then in clean without being disinfected. Spores are thought to be
viable out of the water for up to 2 days (Bower 2006), but cannot withstand being completely
dried out.
There are no other reported incidents of hybridisation of P. leniusculus and other
crayfish but the physiological similarities of P. leniusculus with A. astacus allow them to
mate, although the eggs are infertile (Taugbol, 2006).
There are no documented control agents for the successful management of P.
leniusculus (Holdich et al. 1999). Trapping is size selective and the smaller individuals
remaining take advantage of the lack of competition to grow rapidly (Sibley 2000). Preventing
the further introduction of this species into new bodies of water is one of the few options
available. Educating the public to the environmental risks this species pose and identifying
new populations are key elements to stopping the spread of this species where it is not
wanted. Stebbing et al. (2003, 2004) examined the possibilities of using pheromones to
attract male P. leniusculus into traps. Stringent legislation has been applied to P. leniusculus
in Britain, which effectively makes it a ‘pest’ and bans the keeping of it in Scotland and Wales
and much of England (Holdich et al. 2004), but P. leniusculus continues to spread.
The suitability of P. leniusculus for aquaculture has led to its introduction into many European
countries. In some countries of mainland Europe, especially Scandinavia, P. leniusculus was
introduced directly into water bodies to compensate for the loss of the native A. astacus
caused by outbreaks of A. astaci. Although unregulated movement and stocking of P.
leniusculus is prohibited, these activities continue to occur and are very hard to regulate.
The signal crayfish supports large, commercial and recreational fisheries in the
countries where it has been introduced, especially Sweden and Finland (Ackefors 1999). In
simple economic terms there are now significant benefits to be gained from its introduction
(Kataria 2004), and it is possibly the economic incentive that is driving the illegal stocking of
P. leniusculus.
Another cause of the spread is stocking into fishing lakes to act as a control of weeds
and its subsequent escape into neighbouring waterways.
Pacifastacus leniusculus is an advantageous colonist noted for its ability to travel for
short distances over land between waterways (Holdich & Pockle 2005), although Taugbol
(2006) holds that this method of distribution is not a key factor in the spread of the species.
There are also conflicting views on the propensity of P. leniusculus to colonise large
stretches of water once it is introduced (Holdich & Pockle 2005). Most of the current spread
is therefore due to illegal introductions.
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Pacifastacus leniusculus is highly fecund: an adult female can reach maturity after
only a year, can live for up to 20 years and is capable of producing up to 400 eggs a year.
The high population densities that would be reached in a short space of time are accountable
for the spread of the species in search of food sources.
Neither Portugal nor Norway has any recorded releases of P. leniusculus into their
waterways, yet both have populations of the species. This has been attributed by Holdich
(2003) to the flooding of rivers in Spain and Sweden respectively, where the species has
been stocked and where they have been washed down stream into the host countries.
Although much work has been undertaken to eradicate P. leniusculus, there are no
known solutions to controlling the spread of the species. Intensive trapping has worked to an
extent, especially after targeting berried females in the spawning season (Reeve,2004; Bubb
et al. 2004). The main problem with trapping is that it removes only larger specimens and
misses the juveniles who themselves spawn next year. Some success has been achieved
using natural pyrethroids (Peas & Hiley 2006) but the method would probably be prohibitively
expensive and likely socially unacceptable.
References
Ackefors H. (1998) The culture and capture crayfish fisheries in Europe. World Aquaculture 29, 12-24, 64-67.
Ackefors H. (1999a) Development of crayfish culture in Sweden during 1980s and 1990s. Fiskeriverktet Rapport
1, 59-81.
Ackefors H. (1999b) The positive effects of established crayfish introductions in Europe. In: F. Gherardi & D.M.
Holdich (eds), Crayfish in Europe as alien species. How to make the best of a bad situation. A. A.
Balkema, Rotterdam, pp. 49-.61.
Ackefors H. (2000) Freshwater crayfish farming technology in the 1990s: a European and global perspective. Fish
and Fisheries 1, 337-359.
Alderman D.J. (1997) History of the spread of crayfish plague in Europe, in Crustaceans: Bacterial and fungal
diseasaes. QIE Scientific and Technical Review 15, 15-23.
Arens A., Taugbøl T. (2005) Status of freshwater crayfish in Latvia. Bulletin Français de la Pêche et de la
Pisciculture 376-377, 519-528.
Bower S.M. (2006) Synopsis of infectious disease and parasites of commercially exploited shellfish: crayfish
plague (Fungus Disease). URL: http://;www-sci.pac.dfo-mpo.gc.ca/shelldis/pages/cpfdcy_e.htm
Bubb D.H., Thom T.J. & Lucas M.C. (2004) Movement and sipersal of the invasive signal crayfish Pacifastacus
leniusculus in upland rivers. Freshwater Biology 3, 357-368.
Degerman E., Nilsson P., Nystrom P., Nilsson E. & Olssen K. (2006) Are fish populations in temperatre streams
affected by crayfish? - A field survey and prospects. Environment Biology of Fishes 78, 231-239.
Dukes J.S. & Mooney H.A. (2004) Disruption of ecosystem processes in western North America by invasive
species. Revista Chilena de Historia Natural 77, 411-437
Edsman L. (2004) The Swedish story about import of live crayfish. Bulletin Français de la Pêche et de la
Pisciculture 372-373, 281-288.
Evans L.H. & Edgerton B.F. (2002) Pathogens, parasites and commensals. In: D.M. Holdich (ed.) Biology of
Freshwater Crayfish. Blackwell Science, Oxford, pp. 377-438.
Griffiths S.W., Collen P. & Armstrong J.D. (2004) Competition for shelter among over-wintering signal crayfish and
juvenile Atlantic salmon. Journal of Fish Biology 65, 436-447.
Guan R. & Wiles P.R. (1997a) Ecological impact of introduced crayfish on benthic fishes in a British lowland river.
Conservation Biology 11, 641-647.
Guan R-Z. & Wiles P.R. (1997b) The home range of signal crayfish in a British lowland river. Freshwater Forum 8,
45-54.
Harlioglu M.M. & Holdich D.M. (2001) Meat yields in the introduced freshwater crayfish Pacifastacus leniusculis
(Dana) and Astacus leptodactylus Escholtz, from British waters. Aquaculture and Research 31, 411-417.
Hiley P.D. (2003) The slow quiet invasion of signal crayfish (Pacifastacus leniusculus) in England – prospects for
the white-clawed crayfish (Austropotamobius pallipes). In: D.M. Holdich & P.J. Sibley (eds) Management
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and Conservation of Crayfish. Proceedings of a conference held on 7 November, 2002. Environment
Agency, Bristol, pp. 127-138.
Holdich D.M. (1993) A review of astaciculture: freshwater crayfish farming. Aquatic Living Resources 6, 307-317.
Holdich D.M. (2003) Commentary and references relating to crayfish distribution and crayfish plague in Europe.
Aquatic Living Resouces 6, 307-317.
Holdich D.M. & Pöckle M. (2005) National Biological Information Infrastructure (NBII) and Invasive Species
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URL:
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Holdich D.M. & Reeve I.D. (1991) Alien crayfish in the British Isles. Report for the National Environment Research
Council, Swindon.
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Holdich D.M, Harlioglu M.M. & Firkins I. (1997) Salinity adaptions of crayfish in Brittish Waters with particular
reference to Austropotamobius pallipes, Astacus leptodactylus and Pasifastacus leniusculus. Estuarine,
Coastal and Shelf Science 44, 147-154.
Kataria M. (2004) A cost benefit analysis of introducing the non-native signal crayfish. URL:
http://66.102.9.104/search<q=cache:5SqPbuMKLZEJ:www.bioecon.ucl.ac.uk/7th_paper/Kataria.pdf+inte
rspecific+competition+signal+crayfish&hl=en&ct=clnk&cd=10&gl=uk
Lewis S.D. (2002. Pacifastacus. In: D.M. Holdich (ed.) Biology of Freshwater Crayfish. Blackwell Science, Oxford,
pp. 511-540.
Lowery R.S. & Holdich D.M. (1988) Pacifastacus leniusculus in North America and Europe, with details of the
distribution of introduced and native crayfish species in Europe. In: D.M. Holdich (ed.) Biology of
Freshwater Crayfish. Blackwell Science, Oxford, pp. 283-308.
Nyström P. (1999) Ecological impact of introduced and native crayfish on freshwater communities: European
perspectives. In: F. Gherardi & D.M. Holdich (eds), Crayfish in Europe as alien species. How to make the
best of a bad situation. A. A. Balkema, Rotterdam, pp. 63-85.
Nyström P. (2002) Ecology. In: D.M. Holdich (ed.) Biology of Freshwater Crayfish. Blackwell Science, Oxford, pp.
192-235.
Peay S. & Rogers D. (1999) The peristaltic spread of signal crayfish (Pacifastacus leniusculus) in the River
Wharfe, Yorkshire, England. Freshwater Crayfish 12, 665-676.
Pöckl M., Holdich D.M. & Pennerstorfer J. (2006) Identifying native and alien crayfish species in Europe. Craynet,
47 pp.
Skurdal J., Taugbøl T., Burba A., Edsman L., Söderbäck B., Styrishave B., Tuusti J. and Westman K. 1999.
Crayfish introductions in the Nordic and Baltic countries. In: F. Gherardi & D.M. Holdich (eds), Crayfish in
Europe as alien species. How to make the best of a bad situation. A. A. Balkema, Rotterdam, pp., 193219.
Söderhäll I. & Söderhäll K. (2002) Immune reactions. In: D.M. Holdich (ed.) Biology of Freshwater Crayfish.
Blackwell Science, Oxford, pp. 439-464.
Söderhäll K. (2004) Krasslig kräfta – tvivelaktig import. Miljöforskning 2004-08-10.
Souty-Grosset C., Holdich D.M., Noël P.Y., Reynolds J.D. & Haffner P. (eds) (2006) Atlas of Crayfish in Europe.
Patrimoines naturels, 64, Muséum national d’Histoire naturelle, Paris, 187 pp..
Swahn J.-Ö. (2004) The cultural history of crayfish. Bulletin Français de la Pêche et de la Pisciculture 372-373,
243-251.
Taugbøl T. & Skurdal J. (1999) The future of native crayfish in Europe: How to make the best of a bad situation?
In: F. Gherardi & D.M. Holdich (eds), Crayfish in Europe as alien species. How to make the best of a bad
situation. A. A. Balkema, Rotterdam, pp. 271-279.
Taugbøl T. (2004) Hvordan hindre spredning av signalkreps og krepsepest? Forslag til overvåking- og
tiltaksprogram, spesielt rettet mot vassdragene Store Le, Halden og Glomma. NINA Minirapport 49, 13
pp.
Troschel H.J. & Dehus P. (1993) Distribution of crayfish species in the Federal Republic of Germany, with special
reference to Austropotamobius pallipes. Freshwater Crayfish 9, 390-398.
Unestam, T. 1972. On the host range and origin of of the crayfish plague fungus. Rep. Inst. Freshw. Res.
Drottningholm 52, 192-198.
Westman K. (1995) Introduction of alien crayfish in the development of crayfish fisheries: experiences with signal
crayfish (Pacifastacus leniusculus (Dana) in Finland and the impact on the noble crayfish (Astacus
astacus (L.)). Freshwater Crayfish 10: 1-17.
Westman K. & Nylund V. (1979) Crayfish plague, Aphanomyces astaci, observed in the European crayfish,
Astacus astacus, in Pihlajavesi waterway in Finland. A case study on the spread of the plague fungus.
Freshwater Crayfish 4, 419-426.
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Species name: Red swamp or Louisiana crayfish/crawfish.
Scientific name: Procambarus clarkii (Girard, 1852)
Taxonomic status: Cambaridae / Decapoda / Crustacea /
Arthropoda
Figure 1. Procambarus clarkii dorsal view. (Photo by Manfred Pöckl)
Diagnostic features
Procambarus clarkii can reach 15 cm in total body length (more often 10 cm). Adults are
usually dark red, orange, or reddish brown; blue, yellow, white, and black varieties are also
known. Juveniles may be greenish-brown with a narrow, dark band on either side of the
abdomen, and a broader, lighter band along the dorsal surface. Carapace is rough,
particularly behind the cervical groove. The rostrum is prominent with borders tapering to a
small, triangular acumen. Chelae are red on both surfaces, typically S-shaped and covered
in spines and tubercles, which are more prominent on the upper side; two tubercles are
present on the inner side of the fixed finger. Females have a seminal receptacle (annulus
ventralis) located between bases of posterior walking legs. Sexually active males (Form I
males) have distinct grasping hooks on the ischia of the 3rd and 4th pairs of walking legs
(=4th and 5th pairs of pereopods) that are used to hold females during copulation.
The native distribution of P. clarkii is north-eastern Mexico and the south-central USA
westward to Texas and eastward to Alabama and northward into Tennessee and Illinois
(Hobbs 1972). It has been introduced into: North America (several states of the continental
USA outside its native range and Hawaii, western Mexico), Central and South America
(Belize, Brazil, Costa Rica, Dominican Republic, Ecuador, Venezuela), Asia (mainland
China, Japan, the Philippines, Taiwan), Africa (Egypt, Kenya, Republic of South Africa,
Sudan, Uganda, Zambia), and Europe (Holdich et al. 1999a). As of 2006, it occurs in Europe
in: Austria, Belgium, Cyprus, England, France, Germany, the Iberian Peninsula, including the
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Azores, the Balearic, and the Canary Islands, Italy, including Sicily and Sardinia, Malta,
Switzerland and The Netherlands (Souty-Grosset et al. 2006).
Figure 2. Distribution of Procambarus clarkii populations in Europe. (After Souty-Grosset et
al. 2006)
Habitat and biology
Procambarus clarkii has a relatively short life span, early maturity at relatively small body
size (10 g; Paglianti & Gherardi 2004), rapid growth rates (50 g in 3-5 months; Paglianti &
Gherardi 2004), and high fecundity. Life span is about 4 years under laboratory conditions
but it rarely exceeds 12-18 months in nature (Huner 2002). Sexual maturity is reached after
at least 11 molts but at a very flexible size, ranging from 45 mm total length to 125 mm or
more TL (Huner 2002). Mature males occur in two morphotypes or forms, Form I and Form
II, i.e. sexually or not sexually active form, respectively. Form I males shows prominent
copulatory hooks at the bases of the 3rd and 4th walking legs, cornified gonopodia, and
inflated chelae (Huner 2002), whereas Form II males closely resemble the immature animals.
At lower latitudes, particularly in places with a long flooding period (greater than 6
months), there may be at least two reproductive seasons (in autumn and spring), leading to
two generations per year (Scalici & Gherardi 2007). Fecundity is a function of female size
(Huner 2002). Ovarian eggs vary from 50 in females of 60 mm total length to 300 in females
of 90 mm total length to over 600 in females of 120 mm total length. Pleopodal eggs are
always less numerous than ovarian eggs, ranging between 40 to 500 per female (about four
times those produced by a similarly sized A. pallipes). Pleopodal eggs have an average
diameter of 0.4 mm, the diameter being a function of the size of the mated male (Aquiloni &
Gherardi 2008a). Egg production can be completed within 6 weeks, incubation and maternal
attachment within 2-3 weeks at 22 °C, being seemingly arrested below 10 °C (Huner 2002).
Once hatched, the young crayfish undergo two moults in 2-3 weeks and are able to leave the
female, but will continue to stay with her for up to 8 weeks in a form of “extended parental
care” (Aquiloni & Gherardi 2008b), being attracted by a maternal pheromone (Gherardi
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2002). Unlike the European native Astacus and Austropotamobius species, populations of P.
clarkii contain individuals that are incubating eggs or carrying young throughout the year
(Lindqvist & Huner 1999). This allows P. clarkii to reproduce at the first available opportunity,
which contributes to its colonization success.
Procambarus clarkii is found in waters ranging from brackish (10 ppt) to fresh water.
Reproduction is said to be inhibited, however, by salinities above 5 ppt (Huner 2002). Total
hardness and alkalinity should exceed 50 mg ml-1 as calcium carbonate, but successful
populations are known from cultural ponds with total hardness below 5 mg ml-1. pH should be
in the 6.5-8.5 range, although the species can occur at lower and higher pHs (Huner 2002). It
is able to tolerate dry periods of up to 4 months and waters with low oxygen content and high
temperature (Henttonen & Huner 1999), and can also thrive in habitats disturbed by human
activities. Its ability to withstand environmental extremes is related to its burrowing activity
(Huner & Barr 1984). Although there are reports of complex structures (Gherardi 2002), most
P. clarkii’s burrows are simple in their morphology (a single opening and a tunnel enlarging
into a terminal chamber that hosts no more than two crayfish); mud plugs or chimneys in
some instances stand over burrow openings (Huner 2002) (Figure 3). Burrows rarely extend
more than 1.5 m, although depths of over 2 m have been recorded. Where populations are
dense, a large number of burrows may “honeycomb” an area.
Because of all the above physiological and behavioral properties, P. clarkii is able to
occupy a wide variety of habitats, including subterranean waters, wet meadows, temporary
swamps, marshes, and streams, together with permanent lakes and streams. It is well suited
to artificial systems, such as reservoirs, irrigation ditches, and rice fields. Despite being a
“warm water” species, P. clarkii also thrives in higher, colder latitudes in the USA and Japan.
Altitude seems to be the main physical barrier to the establishment of new populations in
Europe, although it has been found at 1200 m above sea level in Spain. Procambarus clarkii
can survive in water bodies that freeze over in the winter months, e.g. in England (SoutyGrosset et al. 2006).
Radio-telemetric studies conducted in various environmental contexts (e.g. Gherardi
& Barbaresi 2000; Barbaresi et al. 2004b; Aquiloni et al. 2005) showed that the pattern of
movement of P. clarkii is composed of two phases. The first is the “nomadic” phase, without
any daily periodicity, characterized by short peaks of high locomotion; this is alternated with
longer periods of slow or null speed (stationary phases), during which crayfish hide in the
burrows by day, emerging only at dusk to forage (Gherardi 2006). Social behaviors, such as
fighting or mating, usually take place at nighttime. During the wandering phase, crayfish
move up to 3 km per day occasionally over land and cover a wide area (Gherardi &
Barbaresi 2000).
Procambarus clarkii is a polytrophic and opportunistic species. In field, adult
individuals mainly feed on fresh plants (Gherardi and Barbaresi 2008a). The taxonomy of the
consumed plants may vary across sites and seasons in accordance with the diverse species
dominating in each single habitat (Gherardi & Barbaresi 2008a). It also may depend on the
crayfish’s feeding preference based on several properties of the plants, including their
nutritional value, digestibility, morphology (that may make a plant easier to handle and to
consume), and chemical composition (i.e. the absence of chemical deterrents, such as
alkaloids and phenolics) (CroninI 2002). Procambarus clarkii is cannibalistic and often acts
as a scavenger, feeding on dead, dying or immobilized fish and amphibians. It actively preys
on species with slow escape reactions (such as Odonata, Ephemeroptera, and snails) and less on
species with fast escape reactions, such as live mosquito fish (Gambusia affinis) (e.g. Gherardi et al.
2001; Correia 2002; Gherardi & Acquistapace 2007). Detritus is also extensively consumed
(Ilhéu & Bernardo 1993a,b), thus opening up the detritic food chain to higher trophic levels.
Juveniles are known to be more carnivorous than the adults, gradually shifting towards a
more vegetarian diet with growth (Correia 2003).
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Figure 3. Types of burrow dug by Procambarus clarkii.
The main predators of P. clarkii are large birds (e.g. cormorants, crows, herons, and
storks), predaceous fish (e.g. eels), and some carnivorous mammals (e.g. otter). Large
invertebrate predators (e.g. dytiscid beetles) may consume juveniles. The appearance of P.
clarkii in an area often leads to a switch in the predatory habits of some species. In the Lower
Guadalquivir Basin (Spain), before the introduction of P. clarkii, eels mostly preyed upon fish
species (mosquitofish and carp). After crayfish introduction, only 17% of their stomachs (vs.
50% before crayfish introduction) contained other fish species, whereas the dominant prey
item was P. clarkii reaching 67% of occurrence (Montes et al. 1993). Still in southern Spain,
P. clarkii has become an important component of the diet of at least six bird species, in
particular for white storks, night herons, and little egrets, whose diet is composed of up to
80% of crayfish when densities of crayfish are high in the summer (Rodríguez et al. 2005).
Although no quantitative study has been yet made, the appearance of P. clarkii has been
considered responsible for the increase in a number of avian species, like some Ardaeidae,
together with cormorants, in some European areas, such as the Massaciuccoli Lake
(Tuscany) (Barbaresi and Gherardi 2000). In Doñana National Park it has also become the
most common prey category of the otter, Lutra lutra (Delibes & Adrian 1987).
Production
Commercial crayfish culture developed its native state of Louisiana (USA) in the 1950s. By
the late 1960s about 4800 ha was under cultivation, by 1980 22,000 ha, and by 1986 more
than 50,000 ha with an average annual harvest of 30,000-40,000 t (Huner 2002). Cultivation
of P. clarkii is practiced in most southern USA states, but at levels generally less than 700 t
from 1000 ha in any particular state. In 1999, the USA produced about 50,000 tof crayfish,
primarily in Louisiana, of which 30,000-35,000 tonnes came from aquaculture (85%
consisting of P. clarkii). These figures were kept stable until the 2005 Hurricanes (AugustSeptember 2005) that caused a crisis in the crayfish industry. Soft-shelled crayfish
production in Louisiana rose to levels exceeding 200 tonnes per annum in the late 1980s, but
declined sharply in the early 1990s because the internal market failed to develop a profitable
industry and the People’s Republic of China started to export crayfish meat at low price.
Crayfish imported from Spain has appeared in 2000. Similarly, in the late 1980s Louisiana
was the principal supplier of frozen crayfish to Scandinavian markets but since the 1990s it
has been replaced by the People’s Republic of China (production of 22,000 t in 2002) and
Spain.
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1500
4000
Aquaculture
3000
1000
2000
500
Capture (t)
Aquaculture (t x 100)
Capture
1000
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
0
1985
0
Year
Figure 4. Production of freshwater crayfish per species in Europe (data from Ackefors 1999).
The principal producing countries for P. clarkii in Europe are Spain and Sweden, followed by
Russia, Germany, UK, France, Denmark, and Finland. Procambarus clarkii was introduced to
Spain in 1976 and in 1980 Spain harvested 350 t and by 1987 to 4650 t. Current production
figures of between 3000-5000 t/yr are probably an underestimate. Production is higher in
years of high rainfall. In Italy, a population in Massaciuccoli Lake has been exploited by a
fishermen cooperative, but it has met with little success due to low demand from local fish
markets (Gherardi et al. 1999).
Procambarus clarkii was introduced to Kenya’s Lake Naivasha in the early 1970s
probably from Uganda and became very abundant within 5 years. As many as 500 t of
crayfish have been shipped from Kenya to Europe annually. Some P. clarkii are also used for
food in Japan, but the most common use is as household pet.
Ecological impacts
Once introduced into areas without any indigenous ecological equivalent, P. clarkii usually
affects all levels of ecological organization. Its impacts range from subtle behavioral
modifications of resident species to altered energy and nutrient fluxes in the ecosystem.
Impacts at the community level can be strong when P. clarkii experiences little predation or
competition from native predators and has prey that lack efficient defense adaptations to it.
Its modes of resource acquisition and its capacity to develop new trophic relationships,
coupled with its action as bioturbator, may lead to dramatic direct and indirect effects on the
ecosystem (Gherardi 2007).
When P. clarkii replaces an indigenous ecological equivalent, its overall effect can be
strong if, once introduced, it is capable of building high densities. This is largely because P.
clarkii is characterized by high fecundity, fast growth rates, and high physiological tolerances
to changing environmental conditions compared with indigenous crayfishes. Higher survival
rate, hence leading to higher densities and/or larger sizes, is expected when a species is
introduced without a full complement of specific parasites, pathogens, and enemies. Large
body dimensions, in their turn, make crayfish resistant to gape size limited predators (such
as many fish) and agonistically superior in resource fights. As a consequence, because of its
large numbers, coupled with its wide trophic plasticity, P. clarkii exerts a greater direct
(through consumption) or indirect (through competition) effect on the other biota, particularly
on crayfish species, benthic fish, molluscs, and macrophytes (Gherardi 2007).
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Effects on individuals and populations
Several studies have focused on P. clarkii acting as a predator upon a naïve species, either
invertebrate or vertebrate. Most often it showed lethal or sub-lethal effects. For instance, P.
clarkii 1) is able to prey upon the embryos and free swimming larvae of up to 13 amphibian
species (Cruz and Rebelo 2005), 2) takes a significantly shorter time than the indigenous A.
pallipes to capture Triturus vulgaris larvae and Rana esculenta tadpoles (Renai and Gherardi
2004) or 3) is unaffected by the toxins contained in Californian newt (Taricha torosa) eggs
(Gamradt and Kats 1996). Obviously, lethal or sub-lethal effects are mostly due to the
relatively short coevolutionary history between the crayfish and the naïve prey that does not
allow the latter to develop efficient antipredator behaviors, morphological structures, or
chemical repellents. The absence of these mechanisms has been evoked to explain, for
instance, the sharp decline of the California newt recorded in three streams in the Santa
Monica Mountains of southern California after about 10 years from the introduction of P.
clarkii (Gamradt and Kats 1996).
The most commonly documented impact of P. clarkii in competitive interactions is its
aggressive dominance over indigenous crayfish species (Gherardi and Daniels 2004). This
dominance usually translate into a differential capability to compete for vital resources, such
as shelters and result in greater predation and increased mortality in indigenous crayfish
species (e.g. vs. A. pallipes: Gherardi and Cioni 2004; vs. P. acutus acutus: Gherardi and
Daniels 2004).
Population effects on indigenous species may also be caused by indirect
mechanisms, for instance through the transmission of pathogens and diseases. There is an
extensive literature showing that North American crayfish species carry a subclinical infection
of the fungus-like Aphanomyces astaci, the aetiological agent of the crayfish plague (e.g.
Diéguez-Uribeondo and Söderhäll 1993). This disease does not require its host to spread, as
the spores can become attached to damp surfaces and be transported in this manner.
Cosequently, crayfish plague has spread and is still spreading via the hundreds of thousands
of crayfish trappers and their gear. Unfortunately, little attention has been given to
commensals or parasites other than A. astaci. It seems unlikely that these pathogens are
species-specific; so, introduced crayfish might bring a host of organisms that may profoundly
affect indigenous species. Some commensals or parasites of crayfish may affect other
animals, humans included (helminth parasites of vertebrates; bacterial fish diseases, enteric
redmouth; infectious pancreatic necrosis).
Effects on the communities
Because of its omnivorous feeding behaviour, P. clarkii can profoundly modify the trophic
structure of freshwater communities at several levels, often acting as keystone species. It
also displays a wide plasticity in its feeding behavior, switching from detritivore/scavenger to
herbivore/carnivore habits in response to food availability. Even at low densities, P. clarkii
can greatly affect the abundance of some species of submersed macrophytes (N. peltata and
Potamogeton sp) and of snails through direct consumption. Reduction of the macrophyte
biomass is also caused by non-consumptive plant clipping and uprooting. Macrophyte
destruction in nutrient-rich conditions, particularly in eutrophic shallow lakes, is generally
followed by a switch from a clear to a turbid state dominated by surface microalgae, like
Microcystis, growth (Rodríguez et al. 2003). In its turn, this may lead to a decrease in primary
production of macrophytes and periphyton because of reduced light penetration.
Procambarus clarkii may affect periphytic algae in a number of ways that may result
in positive (+) or negative (-) effects by: 1) consuming and dislodging periphyton during
feeding, movement or burrowing (-), 2) reducing the abundance of algivorous invertebrates
(or vertebrates), which can indirectly increase algal abundance (+), 3) fertilizing periphyton
with their faeces (+), and 4) consuming or destroying macrophytes on which some algae
grow (-).
In both lentic and lotic systems, P. clarkii can have direct and indirect negative effects
on the biomass and species richness of macroinvertebrates as the result of several
mechanisms, i.e.: 1) consumption, 2) increased drift through prey escape and incidental
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dislodgment by their foraging, and 3) possible inhibition of invertebrate colonization. Each of
these mechanisms could have different consequences (e.g. direct mortality vs. displacement
to downstream areas) for the local macroinvertebrate assemblage. Gastropoda are the taxon
most affected and are sometimes eliminated. Procambarus clarkii is however selective in its
choice of molluscs, thin-shelled snails being preferred to thick-shelled species because they
are easier to handle (Correia et al. 2005). The direct impact of P. clarkii on non-snail
macroinvertebrates largely depends on the life style and behavior of any single species. In
lentic waters, crayfish predation is weak on species that: 1) move quickly enough to escape
tactile-feeding crayfish (e.g. isopods, amphipods, some Diptera, Heteroptera, and
Coleoptera), 2) circumvent crayfish recognition ability by living in cases (e.g. Trichoptera), or
3) avoid contact by living in the sediment (e.g. some Diptera). In streams, crayfish may have
less predictable effects on invertebrate communities than in lentic waters even if, also in
these systems, slow-moving species are expected to decline (i.e. leeches, dragonflies,
caddisflies, isopods, and molluscs) whereas more mobile prey or prey living in sediments
seem to be less affected by crayfish (i.e. chironomids and stoneflies).
Effects on the ecosystems
The introduction of P. clarkii may alter the pathways of the energy flux in two ways, i.e.
through linkages at several trophic levels as a result of feeding and through increasing the
availability of autochthonous carbon as a food source for higher trophic levels. This was
clearly shown by Geiger et al. (2005) in temporary freshwater marshes in Spain. Before the
introduction of P. clarkii, macrophytes and the associated periphyton were the dominant
primary producers. Only a small portion of the energy was transmitted from them to
herbivores, while most of it was lost to the detritus pool, which accumulated large amounts of
organic matter. Detritivores, mainly macroinvertebrates (oligochaetes, chironomids) and
meiofauna (nematodes, ostracods), used only a small fraction of the deposited material. This
system was characterized by a high diversity of herbivores and consisted of a minimum of
four levels of consumers. Due to the large number of trophic levels and losses of energy to
the detritus pool, the energy transferred to top predators such as birds and mammals was
comparatively low. After the introduction of crayfish, much of the detritus was consumed by
P. clarkii and the energy gained was directly transferred to the top predator level (fish, birds,
and mammals). This resulted in a decreased importance of macrophytes, herbivores, and
primary carnivores but a larger availability of energy for vertebrate predators.
The role that P. clarkii might play through their benthic activity on physical and
chemical characteristics of water and sediments was investigated by Angeler et al. (2001) in
a floodplain wetland in Spain. Procambarus clarkii was hypothesized to affect the ecosystem
processes by 1) recycling sediment bound nutrients and 2) re-suspending sediments
associated with crayfish foraging, burrowing, and locomotory activity (walking, tail flipping).
Compared to the control, the enclosures with crayfish showed a significant increase of both
dissolved inorganic nutrients (soluble reactive phosphorus and ammonia) and total
suspended solids as a result of crayfish bioturbation. At the same time, crayfish reduced the
content of organic matter in the sediment and slightly increased total phosphorus and
nitrogen content in sediments as the effect of its benthic activity.
Impacts on human economy and health
The introduction of P. clarkii has been sometimes assumed to have contributed in a positive
way to human economy by: 1) restoring some traditions proper to the cultural heritage of a
country, e.g. crayfishing; 2) producing some economic benefits for many families in poorly
developed areas, e.g. in Andalusia, Spain; 3) leading to a diversification of agriculture to
include astaciculture, e.g. by crayfish farmers in Spain; and 4) increasing trade between
countries inside Europe as well as between European countries and countries outside
Europe (Gherardi 2007).
There are, however, several examples showing that often the introduction of
commercially valuable crayfish has led to negative results in the marketplace. Despite the
original aim of crayfish farmers in Britain to produce crayfish for export to the Scandinavian
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market where they fetch a high price, most of the exports are now being made with crayfish
harvested from natural waters and not from farming (Holdich 1999).
In several countries,
introduced crayfish have today much lower commercial values than indigenous species, as
exemplified by the Scandinavian market where consumers are willing to pay substantially
higher prices for the indigenous A. astacus than for the naturalized P. leniusculus (Holdich
1999). Crayfishing, in its turn, may produce extensive environmental impacts and associated
costs, as the result of the continuous roaming of fishermen with physical alteration of the
habitat and the capture of non-target organisms (e.g. turtles) in the crayfish traps (Geiger et
al. 2005).
The indirect economic impact of the introduction of North American crayfish is well
illustrated by the consequences of the crayfish plague that, since 1860, has led to reduced
production of A. astacus and A. leptodactylus by up to 90% particularly in Scandinavia,
Germany, Spain, and Turkey. For example, in Sweden 80 tonnes were exported in 1908
(from a total catch of 180 tonnes), but export dropped to 27 tonnes by 1910 (Holdich 1999).
In Finland exports declined from 16 million A. astacus in 1890 to less than 2 million in 1910
(Westman 2002). When the plague spread to Turkey in the 1980s, the annual catch of A.
leptodactylus plunged from 7000 to 2000 t (Köskal 1988). It declined even further in the early
1990s, reaching 200 tonnes in 1991, which virtually eliminated exports from Turkey to
Western Europe (Holdich 1999).
There are several examples of damage to other human activities. Procambarus clarkii
is a recognized pest in rice cultures in various parts of the world.. Damage to rice production
primarily consists of crayfish consuming seedlings, but negative effects derive from the
increased turbidity and decreased dissolved oxygen content due to the crayfish action of
bioturbation (Anastácio et al. 2005a, b, c).
Burrowing by crayfish can be a problem in several agricultural and non-agricultural
areas, such as lawns, golf courses, levees, dams, dykes, and in rivers and lakes. The action
by P. clarkii to “honeycomb” banks leads to structural damage that seriously affects areas
with extensive canal irrigation systems and water control structures (Adão and Marques
1993).
Little attention has been paid to the potential harm that P. clarkii poses to human
health. This species often lives in areas contaminated by sewage and toxic industrial
residues and may have high heavy metal concentrations in their tissues (Geiger et al. 2005);
it was found to bioaccumulate metals such as nickel, lead, and zinc in their tissues and
organs at a significantly higher rate than the indigenous species (Gherardi et al. 2002). Its
potential to transfer contaminants to their consumers, including man, is obviously high. Other
potential harms come from the host of its parasites and commensals, some of them, such as
trematodes of the genus Paragonimus, are potential pathogens of man and of his pets if
crayfish meat is consumed raw or undercooked.
The finding that P. clarkii may consume Cyanobacteria is of increasing concern for
human health (Gherardi and Lazzara 2006). Several Cyanobacteria release a wide range of
toxins and BMAA (β-N-methylamino-L-alanine) that may produce lethal animal and human
intoxications (e.g. Cox et al. 2005). Procambarus clarkii was found to accumulate such toxins
in its tissues (Vasconcelos et al. 2001), being therefore able to transfer them to more
sensitive organisms, man included.
Conversely, P. clarkii is able to control, through predation and competition,
populations of the pulmonate snails Biomphalaria and Bulinus known to host Schistosoma
mansoni and S. haematobium, the agents of human schistosomiasis. Schistosomiasis is one
of the most widespread diseases in Africa: in Kenya alone, it is known to affect 3.5 million
individuals with 12 million more at risk of infection (Ministry of Health, Kenya, unpublished
data).
Control
The same legislation applies to P. clarkii as to other non-indigenous crayfish in Europe. The
import of all live crayfish from abroad, including EU-member states, is banned by customs
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legislation in Ireland, Norway, Sweden, Finland, Spain, France, and Poland, but not in Italy,
Austria, and Germany. In Spain, except in Cantabria and Galicia, recreational fishing is
allowed; commercialization of live animals is banned in a few regional areas (Cataluña, Pais
Vasco, Navarra, and Communidad Valenciana). In Britain it is not permitted to keep in
anywhere, although P. clarkii has yet to be placed on Schedule 9 of the Wildlife &
Countryside Act, which effectively would make it a pest.
Reduction of population sizes may be possible by physical methods, although
eradication is unlikely unless at the very beginning of the invasion process. Mechanical
methods to control crayfish include the use of traps, fyke and seine nets and electric fishing.
Continued trapping is preferrable to short-term intensive trapping, which may provoke
feedback responses in the population such as stimulating a younger maturation age and a
greater egg production. Bait, such as roach, bream, bleak or white bream, may increase the
number of crayfish caught in traps. The use of sexual pheromones to attract males is under
investigation (Aquiloni 2007). Physical methods of control include the drainage of ponds, the
diversion of rivers and the construction of barriers (either physical or electrical).
Chemicals that can be used to control crayfish include biocides such as
organophosphate, organochlorine, and pyrethroid insecticides. The use of Pyblast in UK and
Responsar, Percitox, and DeltrinFlow in Italy is under investigation. Since no biocides are
crayfish-specific other invertebrates, such as arthropods, may be eliminated along with
crayfish, and may subsequently have to be re-introduced. There is cause for concern about
toxin bioaccumulation and biomagnification in the food chain (although this is less of a
problem with pyrethroids).
Possible biological control methods include the use of fish predators, disease-causing
organisms (that infect crayfish), and use of microbes that produce toxins, for example, the
bacterium Bacillus thuringiensis var. israeliensis (Holdich et al. 1999b). However, the use of
predator fish species may be effective (Holdich et al. 1999b). The use of SMRT is under
investigation (Aquiloni et al. 2007).
Most introductions of P. clarkii have been intentional, mainly for aquaculture, but they have
escaped from stocked ponds to naturalise and to colonize ditches and canals nearby
(Gherardi 2006). Not mechanism to prevent the escape of crayfish was present at farms at
this time, and elevated prices encouraged expansion of the industry throughout the entire
Guadalquivir marsh zone and the Doñana National Park. Commercial success led to
secondary illegal introductions throughout the rest of the Iberian Peninsula, France, and Italy
between the 1980s and the 1990s.
The suitability of P. clarkii for aquaculture and fisheries production has led to its
introduction into many European countries. In some countries of mainland Europe, P. clarkii
was introduced directly into water bodies to compensate for the loss of the native A. astacus
caused by outbreaks of A. astaci.
Although much work has been undertaken to eradicate P. clarkii, there are no known
solutions to controlling the spread of the species. Some of the problems are:
• Biological control: Attempts have been made in Kenya to use P. clarkii as a biological
control agent to reduce the numbers of snails that act as intermediate hosts for the
disease-causing organism that causes schistosomiasis (Holdich 1999).
• Live food trade: Commerce in live crayfish from neighboring Spain and more distant
countries including the Far East, the USA and Kenya have been responsible for some
of the introductions of P. clarkii into England, the Netherlands, France, Germany and
Switzerland (Henttonen and Huner 1999).
• Sport fishing: P. clarkii can spread to new areas by anglers using them as bait. Popular
as a bait species for largemouth bass, this is believed to have been the most likely
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cause for its introduction into Washington State (USA) (Global Invasive Species
Database 2006).
• Pet/aquarium trade: The habit of selling P. clarkii alive as an aquarium or garden pond
pet may have accelerated the spread of the species through natural waterways in
Europe (Henttonen & Huner 1999). Procambarus clarkii is also popular in the aquarium
trade.
• Local dispersal, e.g. from Spanish waters into southern Portugal (Henttonen and Huner
1999), may have been also natural; because of its ability to disperse and amphibious
habits (P. clarkii is known to migrate for relatively long distances, even exceeding 3 km
per day; Gherardi and Barbaresi 2000). Its local spread can have been also facilitated
by anglers for local consumption or for use as bait.
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PB, Byers JE, Goldwasser L (1999) Impact: toward a framework for understanding the ecological effects of
invaders. Biological Invasions 1:3–19
Renai B, Gherardi F (2004). Predatory efficiency of crayfish: comparison between indigenous and non-indigenous
species. Biological Invasions 6:89–99
Rodríguez CL, Bécares E, Fernández-Aláez M (2003) Shift from clear to turbid phase in Lake Chozas (NW Spain)
due to the introduction of American red swamp crayfish (Procambarus clarkii). Hydrobiologia 506-509:421–
426
Rodríguez CL, Bécares E, Fernández-Aláez M, Fernández-Aláez C (2005) Loss of diversity and degradation of
wetlands as a result of introducing exotic crayfish. Biological Invasions 7:75–85
Scalici M, Gherardi F (2007) Structure and dynamics of an invasive population of the red swamp crayfish
(Procambarus clarkii) in a Mediterranean wetland. Hydrobiologia 583:309–319
Smart AC, Harper DM, Malaisse F, Schmitz S, Coley S, Gourder de Beauregard A-C (2002) Feeding of the exotic
Louisiana red swamp crayfish, Procambarus clarkii (Crustacea, Decapoda), in an African tropical lake:
Lake Naivasha, Kenya. Hydrobiologia 488:129–142
Souty-Grosset C, Holdich DM, Noel PY, Reynolds JD and Haffner P (editors) (2006) Atlas of Crayfish in Europe,
Museum national d’Histoire naturelle, Paris, 187 p (Patrimoines naturels, 64)
Vasconcelos V, Oliveira S, Teles FO (2001) Impact of a toxic and a non-toxic strain of Microcystis aeruginosa on
the crayfish Procambarus clarkii. Toxicon 39:1461–1470
Vogt G (1999) Diseases of European freshwater crayfish, with particular emphasis on interspecific transmission of
pathogens. In: Gherardi F, Holdich DM, editors. Crayfish in Europe as alien species. How to make the best
of a bad situation? Rotterdam: A.A. Balkema, pp 87-103
Westman K (2002) Alien crayfish in Europe: negative and positive impacts and interactions with native crayfish.
In: Leppäkoski E, Gollasch S, Olenin S, editors. Invasive aquatic species of Europe. Distribution, impacts
and management. Dordrecht: Kluwer, pp 76–100
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ALIEN SPECIES SHEET
Species name: Giant river prawn
Giant freshwater prawn
Malaysian prawn
Figure 1. Giant
river prawn
Scientific name: Macrobrachium rosenbergii De Man, 1879
Family name: Palaemonidae
Diagnostic features
The body of Macrobrachium rosenbergii is usually greenish to brownish-grey. The antennae
are often blue, while the chelipeds are blue or orange. There are 14 somites within the
cephalothorax, covered by a large, smooth and hard dorsal shield (carapace). The rostrum,
which has 11-14 dorsal and 8-10 ventral teeth, is long, normally reaching beyond the
antennal scale, slender and somewhat sigmoid in shape, with the distal part curved slightly
upward. The cephalon contains the eyes, antennulae, antennae, mandibles, maxillulae and
maxillae. The eyes are stalked, except in the first larval stage. The thorax contains three
pairs of maxillipeds, which are used as mouthparts, and five pairs of pereiopods (true legs).
The first two pairs of pereiopods are chelate; each pair of chelipeds are equal in size. The
second chelipeds bear numerous spinules, are robust and slender, and may be excessively
long. The mobile finger is covered with short, dense pubescence. The abdomen has 6
somites, each with a pair of ventral pleopods (swimmerets). The swimmerets of the sixth
abdominal somite are stiff and hard and, with the median telson, serve as the tailfan.
The Macrobrachium rosenbergii species group has recently been separated into two: M.
rosenbergii, native to northern Australia, Papua New Guinea, eastern Indonesia and the
Philippines, and M. dacqueti (Sunier), native to south and south-east Asia, and IndoChina
(Wowor & Ng 2007). According to Wowor & Ng (2007), it is the latter species that is cultured
in America, Asia and Africa. The species has been introduced to many countries in tropical
areas where it is an important aquaculture species.
Habitat and biology
Macrobrachium rosenbergii lives in tropical freshwater environments influenced by brackish
water areas, and can be found in extremely turbid conditions. Gravid females migrate into
estuaries, where the eggs hatch as free-swimming larvae. There are 11 distinct larval stages,
with the diet composed primarily of zooplankton, small worms and the larval stages of other
crustaceans. After metamorphosis, M. rosenbergii assumes a benthic life style and migrates
towards fresh water, even walking across damp land if necessary. Post-larvae and adults are
omnivorous, consuming algae, aquatic plants, molluscs, insects, worms and crustaceans.
Males can reach a total length of 320 mm and females 250 mm.
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Figure 2. Main producer countries of Macrobrachium rosenbergii (FAO)
Production
Global aquaculture production of M. rosenbergii increased from an average of <20 000 t y-1
from 1985-1995 to over 200 000 t in 2005 (Fig. 2). Production is dominated by China (99 111
t in 2005), with India (42 820 t in 2005), Thailand (30 000 t in 2005) and Bangladesh (19 609
t in 2005) also increasing production in recent years. By contrast, capture fishery production
is low and relatively stable (Fig. 3), with Indonesia (4660 t in 2005) and the Philippines (836 t
in 2005) the main countries exploiting the species.
8000
Aquaculture
Capture
6000
200
4000
100
Capture (t)
300
2000
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
0
1985
0
Year
Figure 3. Global trends in the capture fishery and aquaculture production of Macrobrachium
rosenbergii.
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Macrobrachium rosenbergii has been farmed in dozens of countries during the past 30 years,
but there is little information about its colonization in natural waters, and there are no reports
of any economic damage or environmental impact related its introduction (New et al. 2000).
The species does not appear to have established wild populations in Brazil (Magalhães et al.
2005). Possible impacts include:
•
•
competition with indigenous species for food, cover or spawning sites.
introduction of exotic parasites or diseases.
•
•
rapid expansion of use in aquaculture.
transfer of live produce to market.
Main issues
The development of freshwater prawn farming was inhibited in the past by its longer hatchery
phase and lower grow-out productivity compared to marine shrimp. These constraints are
now balanced by the development of a distinct and expanding market niche for freshwater
prawns and a more sustainable approach. Macrobrachium spp. production is less likely than
marine shrimp farming to have a detrimental impact because freshwater prawns are reared
at lower densities. Productivity is generally lower, management is less labour intensive, and
the potential for the abuse or waste of resources is minimal. Specific negative effects of M.
rosenbergii culture on the environment have yet to be documented. Adherence to the FAO
Code of Conduct for Responsible Fisheries would ensure that it remains sustainable and
responsible.
References
FAO, 1995. Code of Conduct for Responsible Fisheries. FAO, Rome, Italy. 41 pp.
FAO, 1997. Aquaculture Development. FAO Technical Guidelines for Responsible Fisheries. No. 5. FAO, Rome,
Italy. 40 pp.
FAO Cultured Aquatic Species Information Programme - Macrobrachium rosenbergii (De Man, 1879)
http://www.fao.org/fishery/culturedspecies/Macrobrachium_rosenbergii/en
FAO/NACA/UNEP/WB/WWF. 2006. International Principles for Responsible Shrimp Farming. Network of
Aquaculture Centres in Asia-Pacific (NACA). Bangkok, Thailand. 20 pp.
Griessinger, J-M., Lacroix, D. & Gondouin, P. 1991. L'élevage de la crevette tropicale d'eau douce. IFREMER,
Plouzané, France. 372 pp.
Jayachandran, K.V. 2001. Palaemonid prawns: biodiversity, taxonomy, biology and management. Science
Publishers, Enfield (NH), USA. 624 pp.
Magalhães, C., Bueno, S.L.S., Bond-Backup, G. et al. 2005. Exotic species of freshwater decapod crustaceans in
the state of São Paulo, Brazil: records and possible causes of their introduction. Biodiversity and
Conservation 14, 1929-1945.
New, M.B., 2002. Farming freshwater prawns: a manual for the culture of the giant river prawn (Macrobrachium
rosenbergii). FAO Fisheries Technical Paper No. 428. FAO, Rome, Italy. 212 pp.
New, M.B. & Valenti, W.C. (eds), 2000. Freshwater Prawn Culture: the farming of Macrobrachium rosenbergii.
Blackwell Science, Oxford, England. 443 pp.
New, M.B., D’Abramo, L.R., Valenti, W.C. & Singholka, S. 2000. Sustainability of freshwater prawn culture. In:
New, M.B. & Valenti, W.C. (eds), Freshwater Prawn Culture: The Farming of Macrobrachium
rosenbergii. Blackwell Science, Oxford, pp. 429-434.
Wickins, J.F. & Lee, D.O'C. 2002. Crustacean farming: ranching and culture, 2nd Ed. Blackwell Science, Oxford,
England. 446 pp.
Wowor, D. & Ng, P.K.L. 2007. The giant freshwater prawns of the Macrobrachium rosenbergii species group
(Crustacea: Decapoda: Caridea: Palaemonidae). Raffles Bulletin of Zoology 55, 321-336.
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Species name: Indian white prawn
Scientific name: Penaeus indicus (H. Milne Edwards, 1837)
(source: FAO)
Diagnostic Features (source: FAO)
Carapace rather smooth, lacking gastrofrontal and hepatic crests; adrostral crest extending
as far as or just before epigastric tooth; rostrum slightly curved at tip and sigmoidal-shaped,
usually bearing 7 to 9 upper teeth (including those on carapace) and 3 to 6 lower teeth;
rostral crest generally slightly elevated in large specimens including adult females (but still
with crest in females slightly higher than in males); postrostral crest extending near to
posterior margin of carapace; gastro-orbital crest distinct, extending over posterior 3/5 distal
2 to 2/3 of distance between hepatic spine and orbital margin. In adult petasma males, third
maxilliped with distal segment about as long as second (ventral view) segment which bears a
tuft of dense long hairs (same length as distal segment)attip. Petasma of males with
distomedian projections strongly curved and overhanging distal margin of costae. Thelycum
of females formed by 2 semi-circular lateral plates, with their median margins forming tumid
lips; anterior process slightly rounded and slightly convex; posterior process elongated and
inserted between anterior part of lateral plates; both anterior and posterior processes rather
distinct. Telson lacking lateral spines. Colour: body semi-translucent, somewhat yellowish
white (small specimens) or greyish green and covered with numerous minute dark brown
dots; eyes light brown and covered with some dark brown mesh-like stripes; rostral and
abdominal dorsal crests reddish brown to dark brown; antennal flagella yellowish; antennular
flagella of same colour as body and covered with many dark spots; legs translucent and
somewhat whitish, pleopods yellowish to pinkish; distal part of uropods yellowish with red
margins. Size: Maximum body length 23 cm (females) and 18.4 cm (males), usually less than
17 cm.
Background and Geographic distribution
Traditional methods of brackish water aquaculture exist in four maritime states in India,
namely West Bengal, Kerala, Karnataka and Goa. In Kerala, on the southwest coast of India,
traditional shrimp farming is practiced with one crop of salt tolerant paddy during the rainy
season (June to September) and one crop of shrimp during the summer season (November
to April). These ponds are tidal; auto-stocking of mixed varieties of shrimp and fish takes
place during high tide. Average total production is 650 kg/ha/yr, the proportion of shrimp
being 71 percent. Within the shrimp harvest, Indian white prawn constituted 36-43 percent.
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Juveniles completely depend upon natural food and harvesting is periodical, during full and
new moon periods. Commercial shrimp farming, with selective stocking of shrimp seeds, was
initiated with the establishment of shrimp hatcheries in the government and private sectors in
India in he late 1980s; these hatcheries produced Penaeus indicus and Penaeus monodon
seeds. In India, P. indicus farming has had to take a back seat due to farmers’ preference for
P. monodon. The contribution of P. indicus to global farmed shrimp production is small –
about 1.2 percent in 2005. Currently P. indicus is mainly cultured in Saudi Arabia, Vietnam,
Iran, and India. (source: www.fao.org)
Figure 1. Distribution of Indian white shrimp. (source: www.fao.org)
Figure 2. Main producer countries of Indian white shrimp (source: FAO)
Habitat and Biology (source: FAO)
The Indian white prawn inhabits the coasts of East Africa, South Africa, Madagascar, the
Gulf, Pakistan, the Southwest and East coast of India, Bangladesh, Thailand, Malaysia,
Philippines, Indonesia, Southern China and the Northern coast of Australia. P. indicus is non-
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burrowing, active at both day and night, and prefers a sandy mud bottom. Adults are
normally found at depths less than 30 m but have also been caught from 90 m. The shrimp
mature and breed mostly in marine habitats and spend the juvenile and sub-adult stages of
30 to 120 mm total length (TL) in coastal estuaries, backwaters or lagoons. Juveniles can
tolerate a much wider range of salinity (5-40 ‰) than adults. On the southwest coast of India
the juveniles support a good commercial fishery in the backwaters and paddy fields.
Geographic variations in size at first maturity are evident and vary from 130 to 149 mm TL. P.
indicus females are highly fecund, ranging from 68 000 to 1 254 200 eggs from females of
140-200 mm TL. There are five stages in ovarian maturation: immature, early maturing, late
maturing, mature and spent. P. indicus belongs to the closed thelycum group and mating
takes place immediately after the females moult. During mating, which normally occurs at
night, the sperm packs (spermatheca) are deposited by the hard-shelled male into the
thelycum of the newly moulted, soft-shelled female. The females carry the spermatheca
during ovarian maturation and the sperms are dispensed at the time of spawning.
Fertilization is external as the ripe ova released by the female become fertilized by the sperm
extruding simultaneously from the stored spermatheca in the thelycum. Depending upon the
temperature, hatching takes place within 8-12 hours after spawning. The nauplii are free
swimming and non-feeding and pass through six moults. The larvae further pass through
protozoea (3 stages), mysis (3 stages), and then to postlarvae, which resemble the adult
shrimp. The postlarvae migrate into the estuaries, settle and feed on benthic detritus,
polychaete worms and small crustaceans, and remain there until they attain 110-120 mm TL.
These sub-adults then return to the sea and get recruited into the fishery.
Production
Figure 1 Global Aquaculture production for Penaeusindicus (FAO Fishery Statistics)
Based upon FAO it appears that the annual aquaculture production of the Indian white
shrimp is increasing while capture production follows a decrease to a stable production.
The major products for export to Japan, USA, the EU and the Middle East are frozen (headon, headless and peeled in block frozen form, IQF and AFD), chilled, together with several
value-added products, such as shrimp pickles, cutlets, ready-to-cook and battered and
breaded ready-to-eat. Sizes that are not suited for export are sold in the domestic market.
White shrimp fetch a relatively lower price than Penaeus monodon. While the average C&F
price for small headless P. monodon (21/25 size) in the USA market was US$ 7-13/kg (20012004), the average white shrimp price in 2004 was US$ 5.5/kg. Its present market price in
Europe is much higher. In Cyprus is being retailed, according to size, at about EURO 18-36/
kg , and even higher.
Sanitary standards are high in all major importing countries, especially with regard to
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antibiotic and chemical residues. The EU market has even higher specifications (zero
tolerance). The market in the USA enforces HACCP standards or Sensory Assessment and
also imposes additional regulations regarding antidumping duties on imported shrimp and the
application of Turtle Excluder Devices (TEDs) on wild shrimp fishing fleets in exporting
countries.
Main issues
In recent years, shrimp farming has generated considerable discussion and debate about its
sustainability and environmental impact. The major issues are:
• Pollution of waterways and groundwater due to pond effluents.
• Loss of agricultural lands due to salinization.
• Destruction of mangroves and misuse of wetlands.
• Social conflicts with other resource users.
• Increased dependence on fish meal for shrimp diets.
• Loss of biodiversity due to increased exploitation of wild seed and brooders.
• Introduction of exotic species.
Governments and the shrimp farming industry have implemented several measures to
reduce these negative impacts. Improved water management practices, strict control over
stocking density, prevention of the salinization of groundwater and the application of
precautionary and ‘polluter pays’ approaches are increasingly being applied, so that shrimp
farming will become an ecofriendly activity. Many farmers are small-scale farmers with ponds
of less than 3 ha in most of the Asian countries and it has been suggested that the
establishment of common effluent treatment systems may assist them to improve. Rural
employment opportunities and other infrastructure facilities increased with the establishment
of shrimp farms.
Production costs in India need to be reduced and efforts to market the cultured shrimp in
domestic markets at reasonable prices need to be promoted. Cooperative farming practices
such as satellite farming would help to ensure proper management of the grow-out system,
with arrangements to buy shrimp from smaller producers. Research should focus on
developing genetically improved SPF and SPR broodstock for the production of fast growing
and high health shrimp.
References
Anonymous. 1978. Larval development of Indian penaeid prawns. Coastal aquaculture, marine prawn
culture, Part 1. CMFRI Bulletin 28, Central Marine Fisheries Research Institute, Kochi, India.
90 pp.
Anonymous. 1991. A manual on shrimp farming. The Marine Products Export Development Authority,
Kochi, India. 47 pp.
Anonymous. 2001. Shrimp aquaculture and the environment- an environment impact assessment
report. Aquaculture Authority of India, Government of India, Chennai, India. 114 pp.
Devaraj. M. 1996. Small scale shrimp hatchery. Technology Transfer Series 9. Central Marine
Fisheries Research Institute, Kochi. 15 pp.
Devaraj. M. 1996. Environment-friendly shrimp farming. Technology Transfer Series.10A. Central
Marine Fisheries Research Institute, Kochi, India. 59 pp.
Flegel, T.W. 2006. Detection of major penaeid shrimp viruses in Asia, a historical perspective with
emphasis on Thailand. Aquaculture, 258:1-33.
Maheswarudu, G., Neelakanta Pillai, N. & Manmadhan Nair, K.R. 2000. Broodstock development and
spawning in Penaeus indicus. pp. 714-721 In V.N. Pillai & N.G. Menon (eds), Marine Fisheries
Research and Management. Central Marine Fisheries Research Institute, Kochi, India.
Mohamed, K.H. 1970. Synopsis of biological data on the Indian prawn Penaeus indicus H. Milne
Edwards, 1837. FAO Fisheries Synopsis No. 94. 20 pp.
Neelakanta Pillai, N., Maheswarudu, G. & Manmadhan Nair, K.R. 2000. Seed production and hatchery
management of Penaeus indicus. pp. 704-713 In V.N. Pillai & N.G. Menon (eds), Marine
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Fisheries Research and Management. Central Marine Fisheries Research Institute, Kochi,
India.
Unnithan, K. A. 1985. A guide to prawn farming in Kerala. CMFRI Special Publication 21. 92 pp.
Vijayan, K.K., Alvandi, S.V., Rajendran, K.V. & Alagarswami, K. 1995. Prevalence and histopathology
of Monodon Baculovirus (MBV) infection in Penaeus monodon and P. indicus in shrimp farms
in the South-East coast of India. Asian Fisheries Science, 8:277-272.
http://209.85.129.104/search?q=cache:jY9d75JgGQYJ:www.fao.org/fi/website/FIRetrieveAction.do%3
Fdom%3Dspecies%26fid%3D2589+penaeus+indicus+fact+sheet&hl=fr&ct=clnk&cd=1
http://www.fao.org/fishery/culturedspecies/Penaeus_indicus#tcN50126
http://www.fao.org/fishery/introsp/2935
Compiled by Daphne Stephanou with information provided by the Cyprus Department of
Fisheries and Marine Research and FAO :
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Species name: Kuruma prawn (En), Crevette kuruma (Fr),
Langostino japonés (Sp), Mazzancolla giapponese (It)
Figure 1. Kuruma prawn
Marsupenaeus (Penaeus)
japonicus
Scientific name: Marsupenaeus (Penaeus) japonicus (Bate
1888)
Family Name: Palaemonidae
Diagnostic features
Males can reach a total length of 190 mm; females 225 mm. Carapace smooth and glossy.
Ten or more brownish transversal bars are present on the upper side of the abdomen.
Uropods present brown, yellow and blue transversal stripes. Rostrum rather straight bearing
8-10 teeth dorsally and 1-2 ventrally. A key taxonomical trait for species identification is the
“papillon” in fertilized females, constituted by a spermatophora pair inserted in the thelycum
on the ventral side of the carapace.
The native range of Marsupenaeus japonicus is the Western Indo-Pacific Sea: Japan (North)
to Australia (South), Fiji (East) to Africa (West). This prawn is currently present in Turkey,
Israel, Lebanon, Cyprus and Egypt as a Lessepsian migrant (Kevrekidis & Kevrekidis 1996).
It was first detected around the island of Rhodes (Greece) in 1995, apparently spreading
from the Mediterranean coast of Turkey (Kevrekidis & Kevrekidis 1996; Galil & Kevrekidis
2002; Kevrekidis & Thessalou-Legaki 2006). However, Yokes et al. (2007) considered it “an
intentional aquaculture introduction” to the Aegean coast of Turkey. It has also been
recorded in the Adriatic sea, coastal areas of the Atlantic sea (Cádiz, SW Spain) and the
Mediterranean Sea (France, Sicily) apparently from escapes from aquaculture installations
(Kevrekidis & Kevrekidis 1996). This species yields ca. 30% of the total fishery catch of
penaeid prawns in the area of Alexandria (Egypt) and 20-30 t/yr in Israel (Kevrekidis &
Kevrekidis 1996).
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Habitat and biology
As for other peneid shrimps, the life cycle of M. japonicus occurs in two different
environments. Adults live in marine coastal waters (0-90 m depth) on sandy/muddy bottoms.
Here mating and spawning take place. Larvae are then transported by currents towards
estuarine coastal areas where development takes place: M. japonicus shows twelve distinct
larval stages (6 nauplius, 3 zoea, 3 mysis). Sexually mature juveniles and subadults migrate
back to marine coastal waters.
Marsupenaeus. japonicus has an infaunal lifestyle being buried in sand during the day
and roaming on the sea bottom for foraging at night. This species is euryhaline and
eurytherm; it is carnivorous for most of its life cycle, feeding mainly on polychaetes, bivalves
and other crustaceans. The average life span is 2 years. Reproduction in subtropical/tropical
climates (its native range) takes place from March to September at about 18 °C water
temperature. Eggs hatch in a temperature range of 27-29 °C in 13-14 hr.
Figure 2. Dstribution map for Kuruma prawn (Penaeus japonicus). Source FAO
Production
First laboratory trials for rearing M. japonicus in captivity were made by the biologist
Motosaku Fujinaga in 1934 (Hudinaga 1942), who succeeded in inducing reproduction and
larval development. However the commercial production of this species in Japan only started
in 1967. This species quickly became one of the most appreciated in Japan with an average
production of 5 t/ha/yr and a market price higher than 70 US$ / kg in the 1990s. Today
market prices in Japan can be > 200 US$ / kg, which is the main reason why,
notwithstanding the high production price (sophisticated fodder types are used to obtain such
a high production rate); the species is now reared in many countries of the world.
Although M. japonicus production started in Japan, this species is now mainly
produced in Taiwan and Korea (Fig. 2). In Europe, Spain is leading the producer of this
penaeid shrimp, followed by Italy, France and Albania (that stopped production in 2001). The
highest production for this species, both in Europe and Asia, occurred in the 1990s, with
22,000 t of kuruma shrimp produced in Taiwan in 1991 and 130 t in Spain in 1996. Generally,
production for this species has declined since the end of the 1990s.
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Figure 2. Global production of Marsupenaeus (Penaeus) japonicus (Source: FAO FISHSTAT).
Semi-intensive farming: postlarvae are stocked at higher densities (28,000-50,000 postlarvae
/ ha) in semi-natural rectangular in shape basins (area = 1-3 ha; depth: 0.8-1.2 m). Water
exchange is mechanically helped by dams and gates. Basins can be drained for harvesting.
Shrimps are fed daily with a mix diet of fresh or dry artificial food, in addition to the existing
natural food resources. Sometimes fertilisers are employed to increase the productivity of the
basin. Water pumps are necessary to keep constant chemical-physical parameters.
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Figure 3. European production of Marsupenaeus (Penaeus) japonicus (Source FAO
FISHSTAT).
Main issues
Marsupenaeus japonicus is a very resistant species. It withstands manipulation in farming
and high survival rates of adults even for long distance delivery. Market size (20 g wwt) is
reached in 5-6 months. It cannot face high salinity and very high temperature, while cold
temperatures are not such a problem for its farming (minimum 5° C). High productivity rates
are obtained in ponds with sandy bottom and highly proteic food (60%). The use of artificial
food rich in protein gives reason to the high production cost for this species, which is mainly
designated to “niche” market.
The production cycle of this species implies a high risk of escape of farmed individuals. Sea
ranching in lagoons (growth and dispersal of juveniles directly into the environment) is
indicated as one of the most successful way of harvesting. That practice bears also the
highest risk of non target associated species introduction in the wild, especially in the case of
sowing post larvae of extra European origin without control or quarantine procedures. M.
japonicus postlarvae are nowadays easily obtained in European local hatcheries that are in
some cases provided with technology which could minimise risk of ectobionts (non target
associated fauna and flora) diffusion. Production of this species is mostly carried out in
brackish water areas, which are also recognised as hot spots of non indigenous species
introduction and xenodiversity. Bad farming practices of this species would easily represent
an important vector of dissemination of non target alien species. Spread of pathogens,
especially WSSV, from farmed to wild crustaceans, has been observed. Escapees could act
as carrier and contaminate wild life; all decapod crustaceans from marine and brackish or
freshwater sources are listed as susceptible species (Mortensen et al. 2007). Moreover,
viruses have been found in frozen commodity shrimp products. Improper disposal of wastes
could provide a source of virus which could contaminate wild off arm stocks in the vicinity of
the waste stream discharge.
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In addition, M. japonicus is a strict carnivorous species, thus its uncontrolled release
and acclimation in the wild would have detrimental effect on the native food web by removing
native soft bottom benthos (Streftaris & Zenetos 2006).
Aquaculture development is the most likely cause of further dispersal of Marsupenaeus
japonicus, although the species can disperse naturally.
References
Canese S., Tosi S. & Ponticelli A. 1989. Esperienze di riproduzione artificiale e di allevamento di gamberi marini
in ambienti lagunari costieri. Terra e Sole 568: 702-731.
FAO Species sheet. http://www.fao.org/fishery/species/2584
FAO, 2007. Fisheries and Aquaculture Information and Statistics Service. www.fao.org
Galil B.S. & Kevrekidis K. 2002. Exotic decapods and a stomatopod off Rhodes island (Greece) and the eastern
Mediterranean transient. Crustaceana 75: 925-930.
Hudinaga M. 1942. Reproduction, development and rearing of Penaeus japonicus. Japanese Journal of Zoology,
10(2): 305-393.
Kevrekidis K. & Kevrekidis T. 1996. The occurrence of Penaeus japonicus Bate (Decapoda, Penaeidae) in the
Aegean Sea. Crustaceana 69: 925-929.
Kevrekidis K. & Thessalou-Legaki M. 2006. Catch rates, size structure and sex ratio of Melicertus kerathurus
(Decapoda: Penaeidae) from an Aegean Sea trawl fishery. Fishery Research 80: 270-279.
Laubier-Bonichon A., Laubier L. 1979. Reproduction controlée chez la crevette Penaeus japonicus. In T.V.R.
Pillay, Dill W. (Eds), Advance in aquaculture. Fishing News Books Ltd, Surrey: 273-277.
Lumare F., 2001. Studio sulla localizzazione di aree potenzialmente idonee alla gambericoltura in provincia di
Cagliari. UNIRIGA (ed), 27 luglio 2001, Lecce: 289 pp.
Mortensen S., I. Arzul, Miossec L., Paillard C., Feist S.W. & Stentiford G.D. 2007. Molluscs and Crustaceans. In
“Scientific review of wild-farmed fish and shellfish disease interactions” Ed. By R. Raynard, Th. Wahli, I.
Vatsos and S. Mortensen, 452 pages, available on-line www.dipnet.info/.
OIE 2006. Manual of diagnostic tests for Aquatic Animals. Fifth edition, 469 pp
Rambaldi E., De Murtas R., Biassoni M., Ottolenghi F., Pelusi P. & Rasset B. 2004. Aspetti tecnico-operativi ed
economici dell’allevamento della mazzancolla (Marsupenaeus japonicus) in bacini artificiali secondo
differenti protocolli produttivi. Incontro scientifico congiunto CoNISMa – AIOL Terrasini (PA), 18 - 22 ottobre
2004, poster.
Shigueno K. 1975. Shrimp culture in Japan. Ed Association for International Technical Promotion, Tokyo, Japan:
153 pp.
Streftaris N. & Zenetos A. 2006. Alien Marine Species in the Mediterranean - the 100 "Worst Invasives" and their
Impact. Mediterranean Marine Science 7: 87-118.
Tosi S. & Ponticelli A. 1990. Gamberi peneidi. Biologia Riproduttiva ed esperienze di riproduzione artificiale con
impiego di acqua ipotermale. Quaderni tecnici di Acquicoltura, Enea, 65pp
Yokes M.B., Karhan S., Okus E., Yüksek A., Aslan-Yilmaz A., Yilmaz I.N., Demirel N., Demir V. & Galil B.S. 2007.
Alien Crustacean Decapods from the Aegean Coast of Turkey. Aquatic Invasions 2: 162-168.
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Species name:Russian sturgeon
Scientific name: Acipenser gueldenstaedti
(Brandt and Ratzeberg , 1833)
Family Name: Acipenseridae
Diagnostic Features
The spiracle is present. The snout is short and blunt. Gill membranes joined to isthmus. The
mouth is transverse and lower lip with a split in the middle. The barbels are attached closer
to the tip of snout than to the mouth and they are unfimbriated. The number of gill rakers
range from 15 to 51, which are not fan-shaped, terminated by a single tip. The number of
dirsal fin rays range from 27 to 51, 18 to 33 in anal fin respectively. The number of dorsal
scutes range from 8 to 18, 24 to 50 lateral scutes, and 6 to 13 ventral scutes. Between the
rows of scutes there are numerous bony plates. The colouration is greyish black, dirty green,
or dark green dorsally. Laterally, it is usually greyish brown, and ventrally, grey or lemon. The
juveniles are blue dorsally and white ventrally.
Russian sturgeon is the largest Danubian sturgeon of family Acipenseridae and may reach
up to 3 m, usually 110-140 cm. Reports of 4 m and about 600 kg in weight may refer to
Acipenser sturio.
The status of some forms and subespecies of this species is now under study. Thus, Birstein
& Bemis (1997) consider all intraspecies forms and subespecies of A. gueldenstaedtii, A.
stellatus, A. nudiventris and of A. ruthenus invalids until detailed morphological and
molecular studies of different forms within these species can be performed. Only if
populations of the same species of sturgeons live in disjunct sea basins (e.g. Caspian and
Black seas), could be considered as subspecies.
Caspian, Black and Azov Seas and the rivers that empty into them (Vlasenko et al., 1989).
It is the largest Danubian species of the genus Acipenseridae, and most widely distributed
anadromous species in the Danube River (Hensel and Holčík, 1997).
The Russian sturgeon is critically endangered.
For aquaculture purposes:
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1. species conservation (potential gene and broodstock bank, production of juveniles)
2. production of caviar and highly valuable meat
Figure 2. Species distribution map for Danube sturgeon(=Osetr) (Acipenser gueldenstaedtii).
it was widely introduced either inside or outside its native range to many states such as
Sweden, Finland, Poland, Estonia (FAO database), Germany, France, Czech Republic
(WSCS) and very probably (not reported) to many other countries.
Habitat and Biology
In the sea, the Russian sturgeon inhabits shallow waters of the continental shelf. In the
rivers, it remains at depths from 2 to 30 m. The larvae are found at considerable depths and
in rapid currents. Besides the main diadromous form, it exist also a freshwater form that does
not migrate downstream to the sea. The Russian sturgeon is a bottom-dwelling molluscfeeder (Corbulomya, Abra, Cardium, Nassa). They also readily consume crustaceans
(shrimps and crabs), fishes (Engraulis encrasicolus, Sprattus sprattus and gobiids) and
polychaetes. The main food items of juveniles are crustaceans, including mysids and
corophiids,
and
polychaetes.
The great majority of the males begin to reproduce at an age of 11 to 13 years, while the
equivalent age for the females is 12 to 16 years (Berg, 1948). In the Volga River, the males
requires two to three years to reproduce again after spawning, while the females take four to
five years. Usually, the spawning run of this species into the rivers begin in early spring,
reaches its peak in mid o later summer and ceases in late autumn. In the Volga River the
spawning period extends from mid-May through early June. The spawning sites are gravel or
stony beds at depths from 4 to 25 m. Spawning occurs at water temperatures range
between 8.9º C and 12º C.
Fish production
The Russian sturgeon accounts for 40 % of the total acipenserid fishes catch in the northern
Caspian region, with a record of 11.980 tons in 1977. In aquaculture, the production data are
not available (FAO) despite its production for caviar and meat purposes and widely
introductions have been occurred. According Williot et al. (1999), production assessment of
stellate sturgeon in western Europe in 1999 was c. 80 thousand tons of meat with expected
caviar production in near future.
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4500
4000
Capture production (t)
3500
3000
2500
2000
1500
1000
500
0
1992
1994
1996
1998
2000
2002
2004
2006
Figure 3. Trends in production of Russian sturgeon (data source: © FAO - Fisheries and Aquaculture
Information and Statistics Service - 03/01/2008)
As mentioned above, sturgeons generally are highly attractive species for aquaculture and
therefore, were widely introduced throughout the European continent (not only). In terms of
any potential adverse effects (e.g. spread of diseases and parasites, competition and/or
predation upon native ichthyofauna, gene introgression) due to its introduction in case of fish
escapees and/or their release back into the wild via stocking programs, according to FAO
database, there are no any adverse effects reported until date.
However, escapees or release of fish of aquaculture origin might cause potential
negative effects in wild sturgeon population in terms of genetic variability losses further
supported by easy and common inter-species hybridization, use of hybrids in aquaculture
etc. Unfortunately, no relevant information exists or has been collected in this field and
genetic and accurate potential impact assessment studies should be of interest in future
sturgeon conservation research.
Aquaculture plays an important role in any sturgeon species conservation (1) directly
by production of juveniles for stocking purposes which nowdays seems to be the essential
management recovery tool for almost all sturgeon species worldwide (see e.g. management
action for A. gueldenstaedtii in Iran where aquaculture is essential in conservation program –
Abdolday, 2004), and mostly (2) indirectly due to production of sturgeon goods such as
caviar and meat in controlled conditions (intensive and/or pond aquaculture) and thus
dramatically help to limit its capture from the wild.
Consequently, the view on the sturgeon introductions outside from native range
should include beside the production of highly valuable goods (saving the wild populations)
also the last possibility of these fascinating fishes to be protect (gene bank) since the status
of most sturgeon species is in many countries of natural range of distribution vulnerable,
endanged or critically endangered (close to be extinct) due to overfishing, loss of natural
habitat for reproduction and interference by other human activities.
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References
Abdolhay, H.Sturgeon stocking programme in the Caspian Sea with emphasis on Iran. FAO
FISHERIES TECHNICAL PAPER, 2004, ISSU 429, pages 133-170.
Bauchot, M.L. - 1987. Poissons osseux. In: W. Fischer and M.-L. Bauchot and M. Schneider (eds).
Fiches FAO d'Identification des espèces pour les besoins de la pêche (Révison 1).
Méditerranée et mer Noire. Zone de pêche 37. . P. 891-1421.. Commission des
Communautés Européennes and FAO, Rome.
Berg, L.S. - 1962 . Freshwater fishes of the U.S.S.R. and adjacent countries.Volume 1.Israel Program
for Scientific Translations Ltd, Jerusalem. 4th edition. . Russian version published 1948.
Birstein, V.J. & W.J. Bemis - 1997. How many species are there within the genus Acipenser? Environ.
Biol. Fish. . 48: 157-163..
Hensel, K, Holčík, J. – 1997. Past and current status of sturgeons in the upper and middle Danube
River. Environ. Biol. Fish. 48: 185-200.
Korzhuev, P.A. - 1941. Oxygen consumption of eggs and young of Acipenser gülvenstädti and A.
stellatus. Izvestiia AN SSSR, Otdelenie Biologii. . 291-302.p.
Svetovidov, A.N. - 1964. Handbook of the fauna of the USSR, fishes of the Black Sea. Izdatel'stvo
Nauka, Moscow. . 550 .p.
Svetovidov, A.N. - 1979. Acipenseridae In J.C. Hureau and Th. Monod (eds.) Check-list of the fishes
of the north-eastern Atlantic and of the Mediterranean (CLOFNAM). UNESCO, Paris. . Vol. 1.
p. 82-84.
Svetovidov, A.N. - 1984. Acipenseridae In P.J.P. Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen
and E. Tortonese (eds.) Fishes of the north-eastern Atlantic and Mediterranean. UNESCO,
Paris. . Vol. 1. p. 220-225..
Vlasenko, A.D., A.V. Pavlov & V.P. Vasilev. - 1989. Acipenser gueldenstaedti Brand, 1833. In The
Freshwater Fishes of Europe, Vol.1, Part II: General Introduction to Fishes. Acipenseriformes.
. 294-345. .. (Ed. J. Holcík) AULA-Verlag Wiesbaden.
Welcomme, R.L. - 1988. International introductions of inland aquatic species. FAO Fish. Tech. Pap.
No. 294. . 318. p..
Williot, P., Sabeau, L., Gessner, J., Arlati, G., Bronzi, P., Gulyas, T., Berni, P. – 2001. Sturgeon
farming in Western Europe: recent developments and perspectives. Aquatic Living Resources
14: 367-374.
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Species name:Fringebarbel (Ship) sturgeon
Scientific name: Acipenser nudiventris
(Lovetzky, 1828)
Diagnostic Features
The snout has an almost perfect conical shape. Snout and caudal peduncle subconical. The
spiracle is present. Gill membranes joined to isthmus. The mouth is transverse and lower lip
continuous, and not interrupted in the middle. The barbels are fimbriate, halfway between tip
of snout and mouth, reaching the later. The number of gill rakers range from 24 to 45. The
number of dorsal fin rays range from 39 to 57, 23 to 37 for anal fin respectively. The number
of dorsal scutes range from 11 to 17, lateral scutes from 49 to 74 (usually more than 50),
and ventral scutes from 11 to 17 (in large specimens, these scutes wear away and are often
almost fully lost). There are no small bony plates between the rows of scutes. The first dorsal
scute is the largest and form an obtuse angle with the profil of head.
Dorsum is greyish green, becoming ligther on the sides. Ventral surface is yellowish-white,
and the fins are greyish.
The maximum body length reported is 221 cm, and weigh of 80 kg and a maximum age of 32
years.
Black, Azov, Caspian and Aral Seas, from which adults ascend the rivers to spawn (Sokolov
& Vasilev, 1989). According to Birstein (1993) it is extinct in the Aral Sea. Therefore, possibly
a small population of this form still exists in Lake Balkhash (Zholdasova, 1997).
In Europe, respectively Danube drainage system, the ship sturgeon was never abundant. It
was recorded in the lower Danube delta and in the middle Danube upstream to Bratislava
(Slovakia) including some tributaries. The ship sturgeon is nowdays very rare in the Danube
River, and only occasionally found in the catch of Romania and Serbia (Hensel and Holčík,
1997). Ship sturgeon completely disappeared from Austrian and Slovak Danube territory,
and in Hungary it is extremely rare. The ship sturgeon is endangered sturgeon species.
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Figure 2. Species distribution map for Fringebarbel sturgeon (Acipenser nudiventris).
Habitat and Biology
The ship sturgeon remains in shallow water, above 50 m, where the bottom is muddy. They
are more abundant in the vicinity of river mouths. The ship sturgeon forms both anadromous
and resident populations, but in the Danube River, only resident population occurred
(Banarescu, 1964).
Juveniles prey on insect larvae (Ephemeroptera, Trichoptera, Odonata and Plecoptera),
other insects, molluscs, and crustaceans. Fully-grown ship sturgeon in the Caspian Sea feed
primarily on fishes, especially gobiids, and in recent years, a basic food item in their diet has
become the introduced crab Rhitropanopus harrisi, which account for as much as 70 % of
the food, by weight. Ship sturgeon enters rivers from March to May and in October to
November. Spawning occurs from the end of April to June coincides with water
temperatures between 12 and 17.9 ºC. Some of non-migratory forms continously remains in
the freshwaters.
Fish production
According to FAO, there is no information available either for aquaculture production or
capture from the wild. The total catch of ship sturgeon from Caspian Sea (Iranian territory
only) ranged about 15thousand tons in 2000 (Abdolhay, 2004). Data presented bellow show
a species proportion from total sturgeon catch between years 1972 to 2004.
There is sporadical information about its introductions (According to Fish Base
reported introduction to China in 1933). However, it was introduced to Czech Republic,
Germany and probably occurs in private aquaculture facilities in some other states (H.
Rosenthal, pers. communication).
Percent of catch (%)
100
80
A. persicus
A. nudiventris
A. stellatus
A. gueldenstaedti
Huso huso
60
40
20
0
1972
1991
1994
2000
2004
Year
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therefore, were introduced throughout the European continent (not only). In terms of any
potential adverse effects (e.g. spread of diseases and parasites, competition and/or
Aquaculture play an important role in any sturgeon species conservation (1) directly
action for A. nudiventris in Iran where aquaculture is essential in conservation program –
Abdolday, 2004 and action plan for conservation of Danubian sturgeons mentioned at the
end, Bloesch, 2006), and mostly (2) indirectly due to production of sturgeon goods such as
There is an adverse ecological effect on the recipient ecosystem if an aquatic species, after its
introduction in a particular country, has been reported to cause habitat degradation, to compete with
native species for spawning habitat, to hybridise with native species threatening species integrity
and/or to prey on native species population resulting in their decline or a depletion of native food
resources.”
References
Artyukhin, E.N. & Z.G. Zarkua. - 1986. On the question of taxonomic status of the sturgeons in the
Rioini River (the Black Sea bassin). Voprosy Ikhtiologii. . 26:61-67.
Banarecu, P. - 1964. Pisces-Osteichthyes. Fauna Republicii Populare Romine. Academiei Republicii
Populare Romine, Bucaresti. 13. Ed.
Bauchot, M.-L. - 1987. Poissons osseux. In: W. Fischer and M.-L. Bauchot and M. Schneider (eds).
Fiches FAO d'Identification des espèces pour les besoins de la pêche (Révison 1).
Méditerranée et mer Noire. Zone de pêche 37. . p. 891-1421.. Commission des
Communautés Européennes and FAO, Rome
Berg, L.S. - 1934. Acipenser gueldenstaedti persicus, a sturgeon from the south Caspian Sea. Ann.
Mag. Nat. His.,Ser. 10. . 317-319.
Berg, L.S. - 1962. Freshwater fishes of the U.S.S.R. and adjacent countries. Volume 1.Israel Program
for Scientific Translations Ltd, Jerusalem. 4th edition. . Russian version published 1948.
Birstein, V.J. - 1993. Sturgeons and paddlefishes: threatened fishes in need of conservation. Conserv.
Biol. . 7:773-787.
Birstein, V.J. & W.J. Bemis. - 1997. How many species are there within the genus Acipenser? Environ.
Biol. Fish. . 48: 157-163.
Borodin, N. - 1936. Acipenser persicus, a sturgeon from the Caspian Sea. Ann. Mag. Nat. Hist., Ser.
9. . 20: 26-28.
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Bronzi, P., Rosenthal, H., Arlati, G., Williot, P., 1999. A brief review on the status and prospects of
sturgeon farming in Western and Central Europe. J. Appl. Ichtyol. 15, 224-227.
Crespo, J., J. Gajate & R. Ponce. - 2001. Clasificación científica e identificación de nombres
vernáculos existentes en la base de datos de seguimiento informático de recursos naturales
oceánicos. Instituto Español de Oceanografia, Madrid, Spain
Hilton-Taylor, C. - 2000. 2000 IUCN red list of threatened species. IUCN, Gland, Switzerland and
Cambridge, UK. . xviii + 61 p.. with 1 CD-ROM.
Reshetnikov, Y.S., N.G. Bogutskaya, E.D. Vasil'eva, E.A. Dorofeeva, A.M. Naseka, O.A. Popova, K.A.
Savvaitova, V.G. Sideleva & L.I. Sokolov. - 1997. An annotated check-list of the freshwater
fishes of Russia. J. Ichthyol. . 37(9): 687-736.
Sokolov, L.I. & V.P. Vasilev. - 1989. Acipenser nudiventris Lovestky, 1828. In The Freshwater Fishes
of Europe.Vol.1, Part II: General Introduction to Fishes. Acipenseriformes.AULA-Verlag
Wiesbaden. (Ed. J. Holcík) . 345-366.
Paris. vol. 1. . :220-225.
Zholdasova, I. - 1997. Sturgeons and Aral Sea ecological catastrophe. Environm. Biol. Fis. . 48:373380.
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Species name:Sterlet sturgeon
Scientific name: Acipenser ruthenus (Linnaeus, 1758)
Diagnostic Features
Snout and caudal peduncle are subconical. Snout length and form is highly variable.
Generally, sterlets with pointed snouts tend to be young specimens, and the average age of
those with blunt snouts is greater. Spiracle is present. Gill membranes joined to isthmus.
Mouth is transverse and lower lip with a split in the middle. Barbels are fimbriate. Basic
meristic and morphometric characters: 14-26 gill rakers, number of rays in dorsal fin range
fro 32 to 48, in anal fin then from 16 to 39. Number of dorsal scutes range from 11 to 17,
lateral scutes from 56 to 71 and ventral scutes from 11 to 18.
There are numerous bony plates between the rows of scutes. Colouration varies greatly.
Back is usually dark greyish-brown, the belly is yellowish white, fins are grey and scutes are
dirty white.
The smallest species of family Acipenseridae. The maximum reported size was 125
cm and a weight of 16 kg. Usually body length is below 100 cm and weigth is about 6 to 6,5
kg (Banarescu, 1964).
There are more synonyms that listed up. Birstein & Bemis (1997) consider that all
intraspecies, forms and subspecies of A. ruthenus described by different authors (see Berg,
1948 and Sokolov & Vasilev, 1989) are invalid until detailed molecular and morphological
studies of different forms within these species can be performed.
The sterlet is a Eurasian freshwater species inhabiting rivers flowing into the Caspian, Black,
Azov, Baltic, White, Barents, and Kara Seas (Sokolov & Vasilev, 1989).
For aquaculture purposes mostly aimed like:
• species conservation (potential gene and broodstock bank, production of juveniles)
• production of caviar and highly valuable meat
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it was widely introduced either inside or outside its native range to many European states
such as Germany, Poland, Sweden, France, Estonia, Finland, Czech Republic and very
probably (not reported) to many others.
Figure 2 . Species distribution map for Sterlet sturgeon (Acipenser ruthenus).
Habitat and Biology
The sterlet is a potamal freshwater fish that seldom occur in large lakes. It inhabits the
lowland and foothill zones of the rivers and usually stays in the current in deep depression in
the riverbed. Small specimens are often encountered in sandy shallows. The two kinds of
spawning sites are the river bed at a depth from 7 to 15 m, and floodplain sites flooded by
the rising spring water, on pebbles and rarely on gravelly-sand bottoms. It generally behaves
as a resident fish. Does not undertake long migrations. Their main food in all rivers is benthic
organisms, mainly insect larvae (Trichoptera, Chironomidae, Ephemeroptera, Plecoptera,
and Simuliidae ), small mollouscs (Sphaeridium spp., Pisidium spp. and Viviparus), annelids,
other invertebrates , and also fish eggs, including those of other acipenserids, are also
included in their diet. Young specimens feeds mainly on trichopteran and chironomid larvae.
In the Volga river near its mouth, gammarids account for over 90 % of the food by weigh in
young specimens. With increasing size, the role of trichopterans increases while that of
chironomidae decreases.
Males reach sexual maturity at an age of 3-6 years old, one to two years earlier than
the females. The spawning periodicity remains open: spawn every year or only after a pause
(shorter for males than for females) of one or more years?. Possibly, in the northern part of
the range, the onset of sexual maturity would be later, and a considerable proportion of the
adult specimens would not reproduce during every spawning season (Sokolov & Vasilev,
1989). During the spring floods they do swim upstream in the river for spawning. Males
appear at the spawning ground before females at the water temperature from 9 to 11 ºC.
Females reach the spawning ground later, at a water temperature from 12 to 13 ºC. The
optimal water temperature for the reproduction of sterlets ranges from 12 to 17 ºC. The
sterlet has the shortest life span (22-24 years old) in the genus Acipenser and females live
longer than males.
Fish production
The sterlet is a very important commercial fish. They were caught with nets, fish traps, willow
baskets, and with barbed lances. At the present time, most of the sterlets captured come
from the Danube River system. Paralelly, even in Danube drainage system, sterlet nowdays
has a very limited range of distribution especially in middle and upper part. It is classified as
extirpated from the German section, and endangered in the Austrian section, vulnerable
nearly endangered in most of other danubian countries. Slight population increase recently
reported is presumably due to increasing water quality and mostly as a result of intensive
Deliverable 2.5
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stocking program (juveniles of aquaculture origin) from the Hungarian side of the Danube
(Hensel, Holčík, 1997).
Fish are usually marketed alive, and rarely refrigerated, frozen or smoked. Males of
this species are used to produce the bester, the first generation hybrid with beluga (Huso
huso) females. The sterlet is an important fish in aquaculture, reaching sexual maturity in
containers filled with warmed water (Sokolov & Vasilev, 1989 ).
80
Aquaculture production (t)
70
60
50
40
30
20
10
06
05
20
04
20
03
20
02
20
01
20
00
20
99
20
98
19
97
19
96
19
95
19
94
19
93
19
19
19
92
0
Figure 3. Trends in production of Sterlet sturgeon (data source: © FAO - Fisheries and Aquaculture
Impacts of introduction and main issues
action for A. transmontanus in USA where aquaculture is essential in conservation program
of white sturgeon – Ireland et al., 2002), and mostly (2) indirectly due to production of
sturgeon goods such as caviar and meat in controlled conditions (intensive and/or pond
aquaculture) and thus dramatically help to limit its capture from the wild.
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References
Banarecu, P - 1964. Pisces-Osteichthyes Fauna Republicii Populare Romine. 13. . Ed: Academiei
Republicii Populare Romine, Bucaresti.
Berg, L.S - 1962. Freshwater fishes of the U.S.S.R. and adjacent countries. Israel Program for
Scientific Translations Ltd, Jerusalem. Volume 1, 4th edition. . Russian version published
1948
Birstein, V.B. & W.E. Bemis - 1997. How many species are there within the genus Acipenser? Environ.
Biol. Fish. . 48: 157-163.
Birstein, V.J. - 1993. Sturgeons and paddlefishes: threatened fishes in need of conservation. Conserv.
Biol. . 7:773-787.
Birstein, V.J., Bemis, W.E & J.R. Waldman - 1997. The threatened status of acipenseriform species: a
summary. Environm. Biol. Fish. . 48:427-435.
Hensel, K. & J. Holcík - 1997. Past and current status of sturgeons in the upper and middle Danube
River. Environ. Biol. Fish. . 48:185-200.
Ireland, CS, Beamesderfer, RCP, Paragamian, VL, Wakkinen, VD, Siple, JT. 2002. Success of
hatchery-reared juvenile white sturgeon (Acipenser transmontanus) following release in the
Kootenai River, Idaho, USA. Journal of Applied Ichthyology 18 (4-6): 642-650.
Reshetnikov, Y.S, N.G. Bogutskaya, E.D. Vasil'eva, E.A. Dorofeeva, A.M. Naseka, O.A. Popova, K.A.
Savvaitova, V.G. Sideleva & L.I. Sokolov - 1997. An annotated check-list of the freshwater
Rochard, E., Castelnaud, G. & M. Lepage - 1990. Sturgeons (Pisces:Acipenseridae); threats and
prospects. J. Fish Biol. . 37 (A): 123-132.
Sokolov, L.I & V.P. Vasilev - 1989. Acipenser ruthenus Linnaeus, 1758. In J. Holcíck (ed.) The
freshwater fishes of Europe, Vol. I, Part. II: General introduction to fishes, Acipenseriformes. .
p: 227-263.. Aula-Verlag.
Nauka . 550 p.. Moscow
Vasilev, V.P. - 1980. Chromosome numbers in fish-like vertebrates and fish. J. Ichthyol. . 20(3):1-38.
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Species name:Starry (stellate) sturgeon
Scientific name: Acipenser stellatus (Pallas, 1771)
Diagnostic Features
The spiracle is present. Snout is greatly elongated and sword-shaped, usually more than 60
% of the head length. Gill membranes joined to isthmus. The mouth is transverse and lower
lip with a split in the middle. The barbels are short and no fimbriate, not reaching the mouth
but nearer to it than to tip of snout. The number of dorsal fin rays range from 40 to 54, in anal
fin range from 22 to 35 rays. The number of dorsal scutes varies between 9 to 16, lateral
scutes between 26 to 43 scutes, and 9 to 14 ventral scutes. The dorsal scutes have radial
stripes and strongly developed spines with the tips directed caudal. Between the rows of
scutes, the body is covered by star plates. The body colouration is blackish-brown dorsally
and laterally. The belly is light, and the ventral scutes are dirty white coloured. The maximum
body length reported was 218 cm (TL) and a maximum weight of 54 kg. They usually range
from 100 to 120 cm and 6 to 8 kg.
Figure 2. Species distribution map for Starry sturgeon (Acipenser stellatus).
I Caspian, Azov, Black, and Aegean Seas, from which it migrates into the rivers (Shubina et
al., 1989). In Europe, stellate sturgeon was always rare. It has been occurred up to the upper
Danubian countries territories (e.g. Austria, Slovakia, Germany, Hungary, occasionally also
Czech Republic), but it is considered as extirpated not only from upper Danube, but also
from the stretch of the middle Danube. The last specimens were captured in 1926 in
Slovakia, in 1965 in Hungary respectively. Construction of Iron Gates dams definitively
Deliverable 2.5
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blocked most of migration possibilities to the middle Danube. This species was never
economically significant in Danube river with the annual catch of only about 7.8 tons in 195819-981 (Bulgaria, former USSR, former Yugoslavia and Romania) (Hensel and Holčík, 1997).
Habitat and Biology
During the daytime they are often encountered in the upper layer, while at night, they are
generally found at the bottom. The starry sturgeon inhabits the coastal sea waters (at depths
from 100 to 300 m in the Caspian Sea) over clayey or sandy and clayey sediments, and the
lowland section of rivers. Feeding habits vary with size, season and specific features of the
water bodies (rivers or sea). The younger individuals feed primarily on crustaceans, while
fishes (Gobiidae, Caspialosa, and Clupeonella) become more important in the diet as the
grey older. Also molluscs, Polychaeta and other invertebrates. Sexual maturity is reached by
males at an age of five or six years. Females mature with an average age of 9.7 years and
rarely spawn more than three times in their lives. Enters rivers from April to June with a peak
period when the water temperature reaches 10º to 15ºC. Eggs laid on beds of scattered
stones, pebbles, gravel and sand. The juveniles stay near the mouth of rivers. Its population
is supported by artificial propagation. Spawn from May to September at a water temperature
of 12º to 29ºC.
Fish production
According to FAO database, there is no introduction and/or production data of stellate
sturgeon from aquaculture sectors reported. However, stellate sturgeon was introduced to
several countries (Czech Republic, Germany, France…?) for aquaculture purposes (mostly
as ornamental fish and limited caviar production). The stellate sturgeon catch from wild is
now limited.
3000
2500
2000
1500
1000
500
0
1992 1994
1996 1998
2000 2002 2004 2006
Figure 3. Trends in production of starry sturgeon (data source: © FAO - Fisheries and Aquaculture
Stellate sturgeon is an attractive species for aquaculture and therefore, was introduced to
several European countries (not only). In terms of any potential adverse effects (e.g. spread
of diseases and parasites, competition and/or predation upon native ichthyofauna, gene
introgression) due to its introduction in case of fish escapees and/or their release back into
the wild via stocking programs, according to FAO database, there are no any adverse effects
reported until date.
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negative effects in wild sturgeon population in terms of genetic variability losses due to e.g.
easy and common hybridization (note: The starry sturgeon interbreed in its natural habits
with Acipenser nudiventris, A. ruthenus and A. gueldenstaedtii). Unfortunately, no relevant
information exists or has been collected in this field. Moreover, genetic and accurate
potential impact assessment studies should be of interest in future sturgeon conservation
research. On the other hand, in case of stellate sturgeon, its existence in the wild is very
rare.
management recovery tool for almost all sturgeon species worldwide, and mostly (2)
indirectly due to production of sturgeon goods such as caviar and meat in controlled
conditions (intensive and/or pond aquaculture) and thus dramatically help to limit its capture
from the wild.
of most sturgeon species is in many countries of natural range of distribution is endangered
or critically endangered (close to be extinct) due to overfishing, poaching, loss of natural
There is an adverse ecological effect on the recipient ecosystem if an aquatic
species, after its introduction in a particular country, has been reported to cause habitat
degradation, to compete with native species for spawning habitat, to hybridise with native
species threatening species integrity and/or to prey on native species population resulting in
their decline or a depletion of native food resources.”
References
Banarescu, P. - 1964. Pisces-Osteichthyes. Fauna Republicii Populare Romine. 13. . Ed: Academiei
Republicii Populare Romine, Bucaresti.
Bauchot, M.-L - 1987. Poissons osseux In W. Fischer, M.L. Bauchot & M. Schneider (eds.). Fiches
FAO d'identification pour les besoins de la pêche. (rev. 1). Méditerranée et mer Noire. Zone de
pêche 37. Vol. II. Commission des Communautés Européennes and FAO, Rome. . p. 8911421..
1948.
Birstein, V.J. & W.J. Bemis - 1997. How many species are there within the genus Acipenser? Environ.
Biol. Fish. . 48: 157-163..
ambridge, UK. . xviii + 61 p.. with 1 CD-ROM.
Kottelat, M. - 1997. European freshwater fishes. Biologia. . 52, Suppl. 5:1-271..
fishes of Russia. J. Ichthyol. . 37(9): 687-736..
prospects. J. Fish Biol. . 37 (A): 123-132..
Shubina, T.M., A.A. Popova & V.P. Vasilev - 1989. Acipenser stellatus Pallas,1771. In The Freshwater
Fishes of Europe, Vol.1, Part II: General Introduction to Fishes. Acipenseriformes. . 394-442..
(Ed. J. Holcík) AULA-Verlag Wiesbaden.
Nauka . 550 p.. Moscow
Paris. vol. 1. . :220-225..
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Species name:European Atlantic sturgeon
Scientific name: Acipenser sturio (Linnaeus, 1758)
Diagnostic Features
Spiracle is present. The snout and caudal peduncle is subconical. Gill membranes joined to
isthmus. The mouth is transverse and lower lip with a split in the middle. Barbels are not
fringed, and at adults, are closer to mouth than to tip of the rostrum. The number of gill
rakers range from 8 to 25 terminated by a single tip. The number of dorsal fin rays range
from 30 to 50, anal fin rays from 22 to 33 rays. The number of dorsal scutes range from 9 to
16, lateral scutes from 24 to 40, and ventral scutes from 8 to 14. Scutes are large and stout,
radially striated and their surface is covered by small spines. Between the dorsal and lateral
scute rows, there are many patches of rhombic denticles. Colour: in adults it varies from
greyish-brown to bluish-black on the dorsum and head. It is paler laterally with hazy dark
blotches of variable intensity. Belly is white, whitish or yellowish. Pectoral fin is yellowish, the
other greyish. Scutes are dirty to white.
The maximum size range from 5.5 to 6 m (TL) and about 1000 kg in weight. Usually it is
about 350 cm TL and 280 kg (males usually 100-150 cm and females 130-215 cm).
Atlantic coasts from Morocco to northern Norway, including North Sea and Baltic. Northern
coasts of Mediterranean and Black Sea. Available data indicate that its reproduction is
confined to European waters. A. sturio is a threatened species close to extinction. Two local
populations of this species still living on the Iberian littoral: one in Cadiz Bay and the other in
the Bay of Biscay (Almaça & Elvira, 2000).
Specimens younger than about three months have small triangular teeth (Mohr, 1952). Three
different species of Acipenseridae, Acipenser sturio, A. naccari and Huso huso (L., 1758)
have been recorded in the past in the Iberian seas and rivers. However, according to Almaça
& Elvira (2000), just one, A. sturio is native to the Iberian Peninsula.
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Figure 2. Species distribution map for Sturgeon (Acipenser sturio).
Habitat and Biology
During its stay at the sea, A. sturio is a littoral species limited mainly to estuaries with muddy
bottoms. Larger specimens occur at depths exceeding 100 m. In the river, younger
specimens about 50 to 100 cm in TL, usually stay within a radius of more than 100 Km of the
river mouth, and in the sea, the majority are caught at depths of 20 to 50 m. Very little is
known about the diet of this species. In the Gironde estuary, juveniles show a strong
preference for polychaeta, mainly represented by Heteromastus filiformis, Polyodora sp. and
some nereids in lower proportions, crustaceans were the second most abundant group of
preys (Brosse et al., 2000). Adult specimens feed on benthic invertebrates (molluscs,
polychaeta, isopods and shrimps, as well on small fishes as Ammodytes spp. and gobiids. In
the Black Sea, adult specimens feed mainly on fishes, and almost exclusively on Engraulis
encrasicolus. Adults do not eat during migration and spawning. A. sturio is an anadromous
species. From January to October with a peak between April to the end of May, mature
individuals leave the sea and enter freshwater to spawn. Southern populations begin to
appear in the rivers sooner than the northern ones. In the Guadalquivir River, the peak
migration of the males occurs two or three weeks before that of the females (Classen, 1944).
The distance of the spawning migration seems to be positively correlated with water level,
and a distance of 1000 Km or more may be covered during years of high water. Spent fishes
immediately return to the sea. In the Gironde River, first spawning migration occurs at age of
12 years (males) to 15 years (females). The young sturgeons usually migrate downstream at
the age of 2-4 years, usually at the end of summer and in autumn. The occurrence of various
age groups of A. sturio, including young specimens, in Lake Ladoga (Berg, 1948) suggests
the
existence
of
a
non-migrant
population
in
this
lake.
Spawning occurs between May and June, and juveniles spend 2 years in the river before
entering sea (Williot el al., 1997). The spawning sites are stones or gravel.
Fish production
According to FAO, there is only limited information concerning the production, respectively
capture of A. sturio from the wild. In terms of aquaculture, A. sturio as endangered species is
held in captivity for artificial reproduction and subsequent rearing of larvae under restoration
programs in France and Germany (Williot et al., 1997). Any other production activities for
commercial purposes are not known, but currently it is in progress a new upcoming action
plan for its restoration and conservation (see note bellow).
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3.5
3
2.5
2
1.5
1
0.5
0
2000
2001
2002
2003
2004
2005
2006
s
action in progress for A. sturio where aquaculture is essential in conservation program,
Rosenthal et al., 2007), and mostly (2) indirectly due to production of sturgeon goods such as
References
Almaça, C & B. Elvira - 2000. Past and present distribution of Acipenser sturio L., 1758 on the Iberian
Peninsula. Bol. Inst. Esp. Oceanogr. . 16 (1-4):11-16.
Banarescu, P. - 1964. Fauna R.P.R.Vol. XIII. Pisces-Osteichthyes Ed. Academiei R.P.R., Bucuresti.
Bauchot, M.-L. - 1987. Poissons osseux In W. Fischer, M.L. Bauchot and M. Schneider (eds.). Fiches
pêche 37. Vol. II. Commission des Communautés Européennes and FAO, Rome. . 8911421. p..
1948.
Brosse, L, E. Rochard, P. Dumond & M. Lepage - 2000. Premiers résultats sur l'alimentation de
l'esturgeon européen, Acipenser sturio, dans l'estuaire de la Gironde. Comparaison avec la
faune benthique. Cybium . 24 (3) suppl.:49-61.
Classen, T.E.A. - 1944. Estudio bioestadístico del esturión o sollo del Guadalquivir (Acipenser sturio
L.). Trab. Inst. Esp. Oceanogr. 19, 112 p..
Crespo, J., J. Gajate & R. Ponce - 2001. Clasificación científica e identificación de nombres
vernáculos existentes en la base de datos de seguimiento informático de recursos naturales
oceánicos. Instituto Español de Oceanografía, Madrid, Spain
Elvira, B. & Almodovar, A. - 2000. Further observations on the morphological characters of Acipenser
sturio L., 1758 from the Iberian Peninsula: A comparison with North and Adriatic Sea
populations. Boletín. Instituto Español de Oceanografía, 16, 89-97.
ambridge, UK. . xviii + 61 p.. with 1 CD-ROM.
Holcík, J., R. Kinzelback, L.I. Sokolov & V.P. Vasiliev - 1989. Acipenser sturio Linnaeus, 1758. In The
Freshwater Fishes of Europe, Vol.1, Part II: General Introduction to Fishes. Acipenseriformes.
. 367-394.. (Ed. J. Holcík), AULA-Verlag Wiesbaden.
Mohr, E. - 1952. Der Stör. Die neue Brehm- Bücherei. 84. Akad. Verlagsgesellschaft Geest and Portig
K.-G., Leipzig.
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prospects. J. Fish Biol. 37 (A): 123-132.
Svetovidov, A.N.1984. Acipenseridae In P.J.P. Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen
Paris. vol. 1. 220-225.
Williot, P., E. Rochard, G. Castelnaud, T. Rouault, R. Brun, M. Lepage & P. Elie - 1997. Biological
characteristics of European Atlantic sturgeon, Acipenser sturio,as the basis for a restauration
program in France. Environ. Biol. Fish. 48:359-370.
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Species name:Beluga (great) sturgeon
Scientific name: Huso huso (Linnaeus, 1758)
Diagnostic Features
Beluga sturgeon is characterised by a moderate and pointed snout turning slightly upward.
The lower lip is not continuous, but interrupted at center. Barbels are typically oval or flat,
leaf- like posteriorly, located very close to mouth from rostrum direction. The most
characteristic morphological feature of beluga is five rows of scutes. The number of dorsal
scutes range from 11 to 14 (first one is the smallest), lateral scutes range from 41 to 52 and
ventral from 9 to 11 respectively. The skin of body back is generally ash-grey, black or
greenish with lighter flanks, and white belly (Banarescu, 1964).
Beluga sturgeon belongs among the largest world fishes. It is a largest sturgeon
species and largest European freshwater fish. Historically, the biggest reported individual
was 10m long and 3200 kg in weight, but this size seems to be doubtful (Pirogovskij et al.,
1989). The individuals having 70 to 80kg for males and 168 to 178kg for females were
commonly reported e.g. from Azov Sea (Pavlov, 1967).
Beluga sturgeon is native to basins of Black and Caspian Seas and Mediterraean.
Historically, beluga was among the most abundant of Danubian anadromous fishes, and it
was the most valuable (Hensel and Holčík, 1997). Unfortunately, the species is currently
classified as extirpated in many countries of original range of distribution such as e.g.
Austria, Croatia, Czech Republic, Hungary, Serbia Montenegro, Slovakia and Slovenia. As
native is still classified from Azerbaijan, Bosnia Herzg, Bulgaria, Georgia, Iran, Italy,
Kazakhstan, Moldova Republic, Romania, Russian Federation, Turkey, Turkmenistan and
Ukraine, but currently the species existence in wild is in many places speculative and
strongly dependent on stocking within national and or international recovery programs (e.g.
Caspian Sea, Abdolhay, 2004). Therefore, the use of aquaculture becomes of fundamental
importance for beluga conservation (see e.g. summary given by Abdolhay, 2004). Not
surprisingly, therefore, this species is currently classified as endangered (Appendix 2) and it
is assumed to be reclassified as critically endangered in a close future (Harald Rosentahl,
World Sturgeon Conservation Society) since the abundance of beluga in the wild continues
dramatically to decline.
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As a very attractive species for aquaculture (the highest value has beluga caviar),
according to FAO database (www.fao.org), beluga was introduced into the Estonia in 1972,
and its hybrids also to Poland (1992) and Israel.
There are several other mostly European states which imported (introduced) beluga
sturgeon from Caspian region (former USSR) such as Germany, Czech Republic, France
and probably some others either for commercial or species conservation reasons.
Habitat and Biology
Beluga sturgeon is a diadromous fish species. In adult phase inhabiting mostly brakish and
coastal marine zone (except of reproduction time) until the water depth about 180m. When
beluga reaches sexual maturity (about 10 to 16 years for males, 13 to 22 years for females),
migrates (not every year – usually once per 5 or 7 years) upstream between April and May
usually in the deepest part of the river to spawn. Spawning period usually coincides with a
high-water period in spring and begins at a water temperature of 6° to 7° C, and it ceased
when the temperature reaches 21° C. The spawning sites are usually in the river bed, at a
depth of 4 to 15 m, with a hard, stony or gravelly bottom. After reproduction, larvae
continuously moving downstream again close to river bottom back to the sea. In marine
environment, beluga is a typical pelagial fish, although its benthic feeding mode is well
known too (Banarescu, 1964).
Beluga is a typical zoobenthivorous fish feeding mostly on largest invertebrates
available (e.g. worms, crustaceans, insects...) during its early life stages. Later on, it
becomes a piscivorous predator at a very early age (with a length of 24 cm in the lower
Danube) feeding predominantly on fishes. Preferent prey items are Alosa spp., Engraulis
encrasicolus, cyprinids (Cyprinus, Leuciscus, Scardinius, and Aspius). Marine fishes, such as
Scomber scombrus, Trachurus mediterraneus ponticus and Sprattus sprattus are important
in it diet between May and September, when the beluga are congregating near the coast
prior to entering rivers; during the autumn and winter they descent into deep regions of the
sea and feeds mainly on Mullus barbatus ponticus, Merlangius merlangus euxinus,
Platichthys flesus flesus and Engraulis encrasicolus.
Fish production
The beluga was one of the most important commercial sturgeon species. The great stocks of
the species were concentred in the Caspian region, but as a result of the presence of dams
along the rivers, illegal fishing, loss of suitable spawning habitat, the natural reproduction of
this species and its existence itself in the Caspian watershed has been reduced to a
historical minimum. At present time, the size of the population is trying to be maintained by
stocking with cultured fishes (Pirogorskii et al., 1989).
In aquaculture, bester, a hybrid of female Huso huso and male sterlet Acipenser
ruthenus, has been successfully cultivated for its high quality eggs.
Deliverable 2.5
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600
500
400
300
200
100
20
06
20
04
20
02
20
00
19
98
19
96
19
94
19
92
0
Figure 2. Trends in production of beluga sturgeons (data source: © FAO - Fisheries and Aquaculture
sturgeon conservation research. On the other hand, in case of beluga sturgeon, its existence
in the wild is sporadical and close being extinct.
management recovery tool for almost all sturgeon species worldwide (for details see e.g.
management action for H. huso in Caspian Sea where aquaculture is essential in
conservation program – Abdolhay, 2004), and mostly (2) indirectly due to production of
sturgeon goods such as caviar and meat in controlled conditions (intensive and/or pond
aquaculture) and thus dramatically help to limit its capture from the wild.
of most sturgeon species is in many countries of natural range of distribution endangered or
critically endangered (close to be extinct) due to overfishing, poaching, loss of natural habitat
for reproduction and interference by other human activities.
There is an adverse ecological effect on the recipient ecosystem if an aquatic
species, after its introduction in a particular country, has been reported to cause habitat
degradation, to compete with native species for spawning habitat, to hybridise with native
species threatening species integrity and/or to prey on native species population resulting in
their decline or a depletion of native food resources.”
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References
Almaça, C & B. Elvira - 2000. Past and present distribution of Acipenser sturio L., 1758 on the Iberian
Peninsula. Bol. Inst. Esp. Oceanogr. . 16 (1-4): 11-16 .
Babushkin, N.Ya., 1964. Biology and fisheries of Caspian beluga. Trudy VNIRO 51: 183-258.
Banarescu, P. - 1964. Fauna R.P.R.Vol. XIII. Pisces-Osteichthyes Ed. Academiei R.P.R., Bucuresti.
Bauchot, M.-L. - 1987. Poissons osseux In W. Fischer, M.L. Bauchot and M. Schneider (eds.). Fiches
pêche 37. Vol. II. Commission
Bemis ,W.E., E.K. Findeis & L. Grande - 1997. An overview of Acipenseriformes. Environ. Biol.Fish. .
48:25-71.
Scientific Translations Ltd. , Jerusalem. Volume 1, 4th edition. Russian version published
1948.
Birstein, V.J., 1993. Sturgeons and paddlefishes: threatened fishes in need of conservation. Conserv.
Biol. 7:773-787.
Birstein, V.J., Bemis, W.E & J.R. Waldman - 1997. The threatened status of acipenseriform species: a
summary. Environm. Biol. Fish. . 48:427-435. Hilton-Taylor, C. - 2000. 2000 IUCN red list of
threatened species. IUCN, Gland, Switzerland and ambridge, UK. xviii + 61 p., with 1 CDROM.
Pirogovskii, M.I., L.I. Sokolov & V.P. Vasiliev - 1989. Huso huso (Linnaeus, 1758). In The Freshwater
Fishes of Europe. , Vol.1, Part II: General Introduction to Fishes. Acipenseriformes 156-201..
(Ed. J. Holcík), AULA-Verlag Wiesbaden.
prospects. J. Fish Biol. . 37 (A): 123-132.
Svetovidov, A.N. - 1984. Acipenseridae . In P.J.P. Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen
and E. Tortonese (eds.). Fishes of the north-eastern Atlantic and Mediterranean. UNESCO,
Paris. vol. 1. :220-225.
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Species name: Meagre
Scientific name: Argyrosomus regius (Asso, 1801)
Family name: Sciaenidae
Diagnostic features
Argyrosomus regius has a relatively big head with elongated body. The mouth is in a
terminal position without barbells, and the eyes are quite small. The lateral line is evident,
extending on to the caudal fin. The second dorsal fin is much longer than first. The anal fin
has a first short spiny ray and a second very thin one. Several branched appendices are
present in the swim bladder, which can vibrate producing a typical 'grunt'. It has very large
otoliths. The body colour is silver-grey, with bronze traits dorsally. The fin base is reddish
brown and mouth cavity yellow-gold. Post-mortem colour brown. The fish can reach up to 2
m in length and 50 kg in weight.
Meagre are widespread all over the Mediterranean Sea, although not very common around
Italy and Greece; the biggest fish are found along the coast of West Africa (Fig. 2). In
Senegal, in the bay of Dakar seems to be the southern limit of the species; big schools of
meagre are found around wrecked ships that were sunk to create habitats for several
commercial species.
Figure 2. Distribution of Argyrosomus regius (Source FISHBASE)
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Habitat and biology
Argyrosomus regius can grow up to 2 m and reach >50 kg. Growth is mainly achieved during
summer; feeding activity is substantially reduced when sea temperatures drop below 13-15
ºC.
During reproduction migration, adult meagre approach the coast line in mid-April.
They penetrate estuaries at the end of May to spawn (anadromous migration). During the
spawning season, males produce a typical deep sound, by pushing their abdominal muscles
against the gas bladder. From mid-June until the end of July they leave estuaries to feed
along the coast. They remain in shallow water until the beginning of autumn. During winter,
meagres return to deeper water.
Juveniles (age 0) leave the nursing areas (estuaries) at the end of summer and
migrate to coastal waters (from 20-40 m) to spend the winter. Starting from mid-May they
return to their estuarine feeding areas. Water temperature is the most important factor that
determines the trophic migration and reproduction of meagre. The arrival of adults and the
departure of juveniles from estuaries (age classes 0, 1 and 2) occurs in May and October
when water temperature is close to 13-14 ºC. The best temperature for the growth of meagre
is between 17-21 ºC, with an acceptable range of 14-23 ºC. A 1.2 m female produces about
800 000 eggs, spawning occurs at 17-22 ºC. Fertilized eggs measure 990 µm in diameter.
After 30 hours the lipid droplet is totally absorbed. At 96 hours the vitellin sac is almost
consumed and the mouth is open. Benthic juveniles of 3.7 cm have been captured, indicating
that pelagic life is quite short. Larvae need temperatures above 20-21 ºC in order to
feed.Juveniles (age 1) eat small demersal fish and crustaceans (mysids and shrimp). When
they reach 30-40 cm, they feed on pelagic fish and cephalopods.
Production
The majority of meagre available on the markets are from capture fisheries (Fig. 2). Catches
slumped in the mid 1990s but have risen to around 8000 t in recent years. Farming of
meagre is exclusive to France, Spain and Italy, and restricted to intensive production in landbased tanks and marine cages. Production has risen slowly from virtually negligible
quantities in 2000 to around 800 t in 2005, more or less equally distributed amongst the three
producer countries.
10000
Aquaculture
Capture
Production
(t )
8000
6000
4000
2000
2005
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
0
Year
Figure 3. Trends in the capture fishery and aquaculture production of meagre
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The main impact of farming meagre will be similar to most aquaculture units, potential
pollution and disease transfer, because of the intensity of its production. There are few data
regarding diseases of this species, but there have been cases of parasitism (such as
Amyloodinium sp.). Prevention is mainly achieved by controlling density and water quality.
The other potential problem is escapes from cages, but this is not considered a major
problem because meagre is indigenous to the Mediterranean basin. Perhaps the biggest
problem will be genetic pollution because juvenile production has only been established in
one farm location, leading to potential inbreeding effects.
•
Setting up of fish farms in new areas could allow escapees, especially form cages in
open waters.
References
Angelini, M., Gilmozzi, M., Lanari, D. & Giorni, G. 2002. Allevamento dell'ombrina bocca d'oro, Argyrosomus
regius (Asso). pp. 13-38 In Ricerca per lo sviluppo dell'acquacoltura toscana. Risultati conseguiti, ARSIA
Pubblicazione Speciale. Associazione Piscicoltori Italiani, Cierre grafica, Verona, Italy.
Lanari, D. & Tibaldi, E. 2003. Ricerca per lo sviluppo dell'acquacoltura toscana. Risultati conseguiti. Associazione
Piscicoltori Italiani, Cierre grafica, Verona, Italy. 209 pp.
Le Roy, Y. 1998. Analyse des captures de maigre (Argyrosomus regius) dans le golfe de Gascogne de 1994 à
1997. Mémoire de fin d'étude, université des sciences et technologies de Lille, France. 17 pp.
Poli, B.M., Parisi, G., Mecatti, M., Lupi, P., Iurzan, F., Zampacavallo, G. & Gilmozzi, M. 2001a. The meagre
(Argyrosomus regius), a new species for Mediterranean aquaculture. 1. Morphological, merchantable
and nutritional traits in a commercial wide size-range. European Aquaculture Society Special Publication,
29:209-210.
Poli, B.M., Parisi, G., Mecatti, M., Lupi, P., Iurzan, F., Zampacavallo, G. & Gilmozzi, M. 2001b. The meagre
(Argyrosomus regius), a new species for Mediterranean aquaculture. 2. Freshness involution and flesh
dietetic traits in large commercial-size fish. European Aquaculture Society Special Publication, 29:211212.
Quèmèner L., 2002. Le maigre commun (Argyrosomus regius). Biologie, peche, marche et potential aquacole.
Editions Ifremer, Plouzané, France. 31 pp.
Quéro, J.C. 1989a. Sur la piste des maigres Argyrosomus regius (Poissons, Scianidae) du golfe de Gascogne et
de Mauritanie. Océanis, 15(2):161-170.
Quéro, J.C. 1989b. Le maigre, Argyrosomus regius (Asso, 1801) (Poissons, Scianidae) en Méditerranée
occidentale. Buletin de la Société Zoologique de France, 114(4):81-89.
Quéro, J.C. & Vayne, J.J. 1987. Le maigre, Argyrosomus regius (Asso, 1801) (Poissons, Perciformes, Scianidae)
du golfe de Gascogne et des eaux plus septentrionales. Revue des Travaux de l'Institut des Péches
Maritimes, 49(2): 35-66.
Quéro, J.C. & Vayne, J.J. 1989. Parlons maigres. Annales de la Société des Sciences Naturelles de la CharenteMaritime, 7(7):869-885.
Quéro, J.C. & Vayne, J.J. 1993. Nouvel indice sur les pérégrinations du maigre. Annales de la Société des
Sciences Naturelles de la Charente-Maritime, 8(2):127-128.
Quéro, J.C. & Vayne, J.J. 1997. Les poissons de mer des péches francaises. Delachaux et Niestlé SA,
Lausanne-Paris, France. 304 pp.
Tixerant, G. 1974. Contribution à l'étude de la biologie du maigre ou courbine Argyrosomus regius (Asso =
Sciaena aquila Lacép.) sur la cote mauritanienne. Thèse d'université d'Aix-Marseille, France. 146 pp.
Tortonese, E. 1975. Fauna d'Italia, Osteichthyes, parte seconda. Edizioni Calderoni, Bologna, Italy. 636 pp.
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Species common name(s): Bighead carp
Scientific name: Hypophthalmichthys nobilis (Richardson, 1845)1
Family Name: Cyprinidae
Figure 1. Bighead carp
Image source: http://mdc.mo.gov/conmag/2003/06/images/19.jpg
Diagnostic Features
Head and mouth are disproportionately large. Bighead carp have long, thin gill rakers that
are not fused and contrast sharply to the long, thin gill rakers that are fused to form a
sponge-like apparatus in the silver carp. Additionally, the ventral keel of bighead carp
extends anteriorly from the vent to the base of the pelvic fins whereas the keel of silver carp
extends anteriorly from the vent to the anterior portion of the breast, almost to the junction of
the gill membranes. Barbels are absent. The eyes of the bighead carp have a more ventral
orientation than the silver carp (Kolar et al. 2005). Colouration of the body is dark grey above
and cream-colored below with dark grey to black irregular blotches on the back and sides. It
should be noted that the blotched or mottled pattern is often lost in turbid water (Kolar et al.
2005). The maximum total published length and weight recorded is 112 cm and 21.3 kg
respectively (FishBase, 2008). Diagnostic: D III/7, A I-III/1-14, Pt I/17, Pv I/7-8. Scales along
the lateral line 114-120.
Habitat and Biology
Bighead carp are bottom feeding fish found mainly in lakes and rivers and feeding largely on
zooplankton as well as larvae and clumps of algae (FishBase, 2008). Little information is
available on bighead carp habitat past larval stage (Kolar et al. 2005). Bighead carp are
found at temperatures between 4-26oC (FishBase, 2008).
Geographic Distribution
Native range: The native range of the bighead carp is western China (Fig. 2).
1
Also known as Aristichthys nobilis. Both names are valid and for consistency with recent publications with
have opted for Hypophthalmichthys nobilis.
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Figure 2. Distribution of bighead carp Hypophthalmichthys nobilis worldwide. Native range is khaki
and introduced range is orange (source Fishbase).
Bighead carp has been introduced to a number of countries mainly for aquaculture purposes,
resulting in a near global distribution. The first recorded introduction into Europe was during
the 1960’s, however, date and origin of introductions are unknown for a number of European
countries (Latvia, Slovakia, Denmark, Sweden, Greece, Czech Republic, Bulgaria and
Austria). Introductions were made from China and the USSR into Romania, Hungary and
Yugoslavia during the early 1960’s for aquaculture purposes. Bighead carp has become
established in over half of its European range irrespective of time or reason for introduction
(Fig.3). Its introduction into Germany was made as early as 1964, where it remains nonestablished; it took until 1983 to spread via diffusion into the Netherlands where it is now
thought to have become established. Its breeding requirements are very specialised and
stocks are often maintained by artificial reproduction or continuous importation. It has been
repeatedly stocked into Italy for use in angling; sport is also one reason for its introduction
into Poland (1965) and the UK as late as 1990. Weed control and phytoplankton/pest control
was one of the reasons for its introduction into France in 1975 and Switzerland in 1970
respectively. There are records of pre 18th century introductions of bighead carp from China
into Taiwan. Introductions into Japan and Malaysia are recorded for the 1800s. Bighead carp
became widespread for aquaculture throughout South East Asia and the Middle East by the
mid 20th Century, and as late as 1987 in India. Its establishment is highly variable and
appears to be independent of geography or time since introduction. Aquaculture is by far the
most common reason for introduction; others reasons are limited to weed control (in addition
to aquaculture) in Sri Lanka, research in Fiji and fisheries in Mozambique and India (in
addition to aquaculture) (FishBase, 2008).
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25
Number of introductions .
20
15
10
5
0
Africa (4)
Asia (25)
Europe (20)
Former
USSR (9)
North
Oceania (2)
South
America (6)
America (8)
Figure 3. Histogram of the number of bighead carp Hypophthalmichthys nobilis introductions per
sector (aquaculture black, angling/sport horizontal lines, fisheries vertical lines, biological control grey,
other white) for each FAO region. The category “other” includes ornamental, research, accidental and
unknown. The total number introductions in each FAO region is given in brackets as well as the total
number of populations established in the wild (white circles).
Economic uses and fish production
Despite its frequent use in phytoplankton control, by far the most common reason for its
introduction has been for aquaculture. Other economic uses include sport and angling,
phytoplankton, weed and other pest control, as well as fisheries and research (Fig.3). A few
countries (e.g., Albania, Czech Republic, India, Italy, Mozambique, and Slovakia) imported
the species to augment wild fisheries (FishBase, 2008).The global production of bighead
carp is still increasing (Fig. 4) however the European production was at its maximum at the
end of the eighties and start of the nineties (Fig.5). In 2004, the main EU producers were
Ukraine (2,500 t), Romania (867 t), Czech Republic (564 t) and to a lesser extent Bulgaria
(440 t). Bighead carp are said to be an important source of revenue for catfish farmers when
catfish prices are low (Stone et al., 2000 in Kolar et al. 2005). The net benefit (after
subtracting production expenses) of stocking bighead carp with catfish has been estimated at
$108-183/0.4 ha (Engle and Brown, 1998 and Engle, 1998) and $371/0.4 ha (Jensen, 1998)
(in Kolar et al. 2005).
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Figure 4 shows the rise of bighead carp Hypophthalmichthys nobilis production over time. Bighead
carp was the second most important aquaculture species in 1975 and, although not in the top ten,
remains an important contributor to global aquaculture today.
(source http://www.fao.org/fishery/statistics/global-production).
Production in tonnes (t) .
14000
12000
10000
8000
6000
4000
2000
0
1950
1960
1970
1980
1990
2000
2010
Time
Figure 5. European production of bighead carp Hypophthalmichthys nobilis over time.
(source http://www.fao.org/fishery/statistics/global-production).
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For the majority of bighead carp introductions, no records of impacts exist. Information on
ecological effects has been reported for only 16 per cent (n = 12) of bighead carp
introductions, with varying degrees of certainty. Of these, three were considered to have
beneficial ecological effects and only two were reported as having some level of ecological
impact. Interestingly, an ecological impact occurred in Switzerland where bighead carp
introduction had been intended for positive ecological effects, through the control of
phytoplankton and other pests. Impact does not appear to be influenced by whether bighead
carp also become established in any particular location; in fact the largest proportion of
impact reported cases are those that have resulted in fish remaining non-established whilst
still having an ecological impact (n=5). Five out the 12 ecological impact reported cases
resulted in a beneficial economic impact, the majority of which were introduced for
aquaculture and in one case for Fisheries and Research (FishBase, 2008).
There is very little literature published on the impacts of bighead carp. Bighead carp are often
stocked together with silver carp to control phytoplankton and improve water quality.
However, the data has been conflicting. In some studies bighead carp increased algal
density in ponds whereas in others no difference was recorded. Bighead carp may reduce
blue-green algae blooms (Henderson 1978, 1983, Opuszynski and Shireman, 1993 in Kolar
et al., 2005). Competition for food resources between Hypophthalmichthys and other
planktivorous fishes has been documented in polyculture conditions (e.g., with Catla and
Rohu; Alikunhi and Sukumaran 1964; Dey et al. 1979, in Tripathi 1989; with Common Carp;
Opuszynski 1981 in Kolar et al. 2005). The majority of studies have not quantified diet
overlap or competition for native food resources. A large body of circumstantial evidence is
building, particularly with regards to competition with native fishes that rely on plankton as a
food source (Kolar et al. 2005). Buck et al. (1978a, b) found that production of bighead carp
was inversely correlated to production of silver carp (in Kolar et al. 2005). Lever (1996)
reported that “introduction of bighead carp caused significant changes in diversifying number
of cultured fish species as well as fish community structure in Vietnam”.
Control options
Several control options have been considered or explored in the US such as bioacoustic
barriers that combine sound and bubbles and are effective if proper sound frequencies are
employed Pegg et al. (2004). The most thoroughly researched population control for silver
carp in the US is the use of pesticides. However, this presents the problem of selectivity and
remains environmentally unsound.
References
FAO (2007) The State of World Fisheries and Aquculture 2006
st
(ftp://ftp.fao.org/docrep/fao/009/a0699e/a0699e.pdf) Accessed 21 January 2008.
st
FishBase (2008) (http://www.fishbase.org/search.php) Accessed 21 January 2008. Kolar, C., D.
Chapman, et al. (2005). Asian Carps of the Genus Hypophthalmichthys (Pisces, Cyprinidae) A Biological Synopsis and Environmental Risk Assessment, U.S. Fish and Wildlife Service: 1183.
Kolar, CS; Chapman D; Courtenay, WR; Housel, CM; Williams, JD; Jennings, DP (2005). Asian Carps
of the Genus Hypophthalmichthys (Pisces, Cyprinidae) - A Biological Synopsis and
Environmental Risk Assessment, U.S. Fish and Wildlife Service: 1-183.
Lever, C., 1996. Naturalized fishes of the world. Academic Press, California, USA. 408 p
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ALIEN SPECIES SHEET
Species name: Goldfish
Figure 1. Varieties of goldfish. Photo B shows brown, gold, Shubunkin morphs (Photos:
G.H. Copp)
Scientific name: Carassius auratus (Linnaeus)
Family name: Cyprinidae
Diagnostic features
The goldfish is a moderately deep-bodied fish, with a thick and short caudal peduncle. The
head is scaleless, the snout longer than the diameter of the eye, and there are no barbels
around the mouth. The dorsal fin is long-based, with 3–4 spines and 14–20 soft rays, while
the anal fin has 2–3 spines and 4–7 soft rays. Colouration of wild specimens is highly
variable, but usually olive-brown or olive-green with a bronze sheen. Ornamental varieties
vary through scarlet, red-pink, silver, brown, white, black and combinations of these colours.
The goldfish is native to central Asia, China and Japan, but has been imported throughout
the world as an ornamental species, with introductions to the wild often occurring through the
release of unwanted pet fish (Wheeler 1998, Copp et al. 2005). Self-sustaining populations
listed as having become established in virtually all European countries (Elvira 2001),
although in some cases goldfish is listed, but not gibel carp, as established despite there
being numerous scientific papers published on gibel population biology in those countries
(e.g. Czech Republic, Slovakia, Hungary). This suggests a similar problem of misidentification between brown goldfish and gibel carp as reported for the UK for brown goldfish
and crucian carp (Wheeler 2000). Goldfish has also established populations on other
continents, including Australia (Arthington et al. 1999, Koehn & MacKenzie 2004) and North
America (e.g. Rixon et al. 2005). The countries where goldfish is established, according to
the FAO Dias database (http://www.fao.org/fishery/topic/14786) are shown in Figure 2
Habitat and biology
Feral goldfish populations can be found in lakes, ponds, canals, ditches as well as slowflowing water courses, with the incidence in water courses increasing in recent decades
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(Copp et al. 2006). The species feeds on a wide range of food, including plants, small
crustaceans, insects and detritus. Spawning usually occurs among aquatic vegetation, when
water temperatures approach 20 ºC, with the species characterized by repeated spawning
characteristic (Gillet et al. 1977) and with such a variable gonado-somatic relationship that it
may not be a reliable measure or gonad size during all times of the year (Delahunty & de
Vlaming 1980). Goldfish hybridize readily with the common carp (Cyprinus carpio) and
crucian carp (Carassius carassius), and is said to lead to the decline of the latter species
(Wheeler 2000, Hänfling et al. 2005, Smartt 2007).
Endemic
Introduced
Figure 2. Distribution of Carassius auratus worldwide (source FAO DIAS database).
Fish production
Aquaculture production of goldfish has declined from over 10 000 t y-1 in the late 1980s to
2000-3000 t y-1 in the last decade (Fig. 3). The main producer is Romania (mean >1800 t y-1,
1995–2005), with the Ukraine also increasing its production in recent years (118–1900 t y-1,
1998–2005). Capture fishery production has declined from almost 10 000 t y-1 in the late
1980s to 2000–4000 t y-1 in the last 15 years (Fig. 2). The capture fishery sector is dominated
by Romania (1917 t in 2005), with the Ukraine (1017 t in 2005) also contributing substantial
amounts.
Production (t)
15000
Aquaculture
Capture
10000
5000
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
0
Year
Figure 3. Trends in the capture fishery and aquaculture production of goldfish in Europe.
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The goldfish can pose a high risk to both still and running waters (Morgan & Beatty 2004),
although ponds appear to be at the greatest risk of impacts because of goldfish introductions
(Richardson et al. 1995; Copp et al. 2005). The species can reproduce in its second year of
life (Tarkan et al. unpublished), with repeated spawning with a vegetative season (Gillet et al.
1977), which allows the species, with a short period, to invade small water bodies (Copp et
al. 2005) as well as water courses (Morgan & Beatty 2004). Consequences for native
species include genetic contamination through hybridization (Wheeler 2000, Hänfling et al.
2005, Smartt 2007) and for the recipient ecosystems the impacts include increased turbidity
(Richardson et al. 1995). The main issues are:
•
•
•
•
competition with indigenous fish for food, cover or spawning sites.
hybridization with native species (i.e. crucian carp), potentially leading to their decline.
increases in water turbidity due to re-suspension of silt deposits.
the introduction of exotic parasites or diseases.
•
valued as ornamental fish for ponds and aquaria, with a demonstrated human propensity
to release the species into open waters, usually as unwanted pet fish (Copp et al. 2005,
2006).
References
Arthington A.H., Kailola P.J., Woodland D.J. & Zalucki J.M. (1999) Collection of Baseline Environmental Data
(relevant to an evaluation of Quarantine Risk Potentially Associated with the Importation to Australia of
Ornamental Finfish). Report to the Australian Quarantine and Inspection Service, Department of
Agriculture, Fisheries and Forestry, Canberra, ACT. 451 pp.
Copp G.H., Wesley K.J. & Vilizzi L. (2005) Pathways of ornamental and aquarium fish introductions into urban
ponds of Epping Forest (London, England): the human vector. Journal of Applied Ichthyology 21, 263–
274.
Copp G.H., Stakėnas S. & Davison P. (2006) The incidence of non-native fishes in water courses: example of the
United Kingdom. Aquatic Invasions 1, 72–75.
Delahunty G. & de Vlaming V.L. (1980) Seasonal relationships of ovary weight, liver weight and fat stores with
body weight in the goldfish, Carassius auratus (L.). Journal of Fish Biology 16, 5–13.
Gillet C., Billard R. & Breton B. (1977) Influence de la temperature sur la reproduction du poisson rouge
(Carassius auratus L.). Cahiers du Laboratoire de Montereau 5, 25–42.
Hänfling B., Bolton P., Harley M. & Carvalho G. R. (2005) A molecular approach to detect hybridisation between
crucian carp (Carassius carassius) and non-indigenous carp species (Carassius spp. and Cyprinus
carpio). Freshwater Biology 50, 403–417.
Koehn J. & MacKenzie R.F. (2004) Priority management actions for alien freshwater fish species in Australia.
New Zealand Journal of marine & Freshwater Research 38, 457–472.
Morgan D. & Beatty S. (2004) Fish fauna of the Vasse River and the colonisation by feral goldfish
(Carassius auratus). Report to Fishcare WA and Geocatch. (available at:
http://www.issg.org/database/species/references.asp?si=368&fr=1&sts=)
Richardson M.J., Whoriskey F.G. & Roy L.H. (1995) Turbidity generation and biological impacts of an exotic fish
Carassius auratus, introduced into shallow seasonal anoxic ponds. J. Fish Biology 47, 576–585.
Rixon C.A.M., Duggan I.C., Bergeron N.M.N., Ricciardi A. & MacIsaac H.J. (2005) Invasion risks posed by the
aquarium trade and live fish markets on the Laurentian Great Lakes. Biodiversity & Conservation 14,
1365-1381.
Smartt J. (2007) A possible genetic basis for species replacement: preliminary results of interspecific hybridisation
between native crucian carp Carassius carassius (L.) and introduced goldfish Carassius auratus (L.).
Aquatic Invasions 2, 59–62.
Tarkan A.S., Copp G.H., Cucherousset J. & Godard M. (in preparation) Growth and reproduction of introduced
goldfish Carassius auratus in small ponds of southeast England. (unpublished manuscript)
Wheeler A.C. (1998) Ponds and fishes in Epping Forest, Essex. The London Naturalist 77, 107–146.
Wheeler A.C. (2000) Status of the crucian carp, Carassius carassius (L.), in the UK. Fisheries Management and
Ecology 7, 315–322.
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Species name:African catfish
Sharptooth catfish
Scientific name: Clarias gariepinus Burchell
Synonym : Clarias lazera Valenciennes
Family Name: Clarridae
Diagnostic features
Clarias gariepinus is usually dark, although dorsal colour can vary from sandy-yellow through
grey to olive with dark greenish-brown markings; it is cream-white ventrally with a distinctive
dark longitudinal band on each side of the ventral surface of the head, although this is absent
in young fish. The species has long dorsal and anal fins; without dorsal fin spine and adipose
fin. The head is large, depressed and heavily-boned, with small eyes. The mouth is
terminally large and with four pairs of barbels. The gill openings are wide; an air-breathing
labyrinthic organ arises from the gill arches. The first gill arch has 24 to 110 gillrakers. The
adult’s head is coarsely granulated, whilst the head of the young is smooth.
Clarias gariepiunus is a widespread African freshwater fish species with a native range from
southern Natal (South Africa) and the Orange River northwards through Central, West and
North Africa, the Middle East and into Eastern Europe. The range has been extended
through translocations by aquaculturists, farmers, anglers and engineers; there are many
South African rivers where it does not occur naturally and where it is now an invasive species
(Cambray 2003).
Introduced
Endemic
Figure 2. Distribution of Clarias gariepiunus worldwide
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Habitat and biology
Clarias gariepiunus lives in a variety of freshwater environments, including still waters, such
as lakes, ponds and pools. It is prominent in rivers, rapids and around dams, and may be
found at depths of 4-80 m. The species has the ability to adapt to extreme environmental
conditions and can live in a pH range of 6.5-8.0. It is also able to live in very turbid waters
and can tolerate temperatures of 8-35°C, although its optimal temperature for growth is 2830°C (Teugels 1986). The presence of an accessory breathing organ enables this species to
breathe air when very active or under very dry conditions.
The species is mainly a benthic feeder, but occasionally forages in surface waters.
Clarias is omnivorous and preys on a wide variety of animals, including fish, birds, frogs,
snails, crabs and shrimps. It also feeds on detritus, plant material and small aquatic
invertebrates, and can filter-feed on plankton. There is, therefore, an issue of predation on
indigenous fish populations (Vitule et al. 2006). C. gariepiunus can live in very poorlyoxygenated waters, and if the gills collapse or become clogged it has the ability to secrete
mucus to keep the skin moist. It is also capable of burrowing into the sediments of drying
waterbodies (Skelton 1993). Spawning takes place during the rainy season (July to
December) in flooded deltas.
Fish production
Clarias gariepinus is one of the most important commercial freshwater fishes in Africa. Global
capture has more than doubled in the past 50 years, from 17 500 t in 1955 to 46 789 t in
2005, highlighting the increasing importance of the species in recent years (Fig. 3). Countries
with the largest catches in 2005 were Mali (25 000 t) and Nigeria (18 938 t). By contrast,
production of Clarias in aquaculture has only expanded since the 1980s (Fig. 4), with a sharp
increase in global production since 2000 (Fig. 4). Features of the species that make it
desirable for introduction into fisheries include a high growth rate and resistance to handling
and stress. Clarias gariepinus has good organoleptic qualities and is one of the most suitable
species for aquaculture in Africa. The species is marketed live, fresh and frozen; eaten
broiled, fried and baked.
Global
Europe
Capture
Production (tonnes)
50000
40000
30000
20000
10000
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
0
Year
Figure 3. Trends in global (solid line) and European (dashed line) aquaculture production of Clarias
compared with capture production (stippled line).
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Clarius gariepiunus has been extensively introduced for aquaculture and sport fishing
throughout the world. The species is large and highly predatory, thus posing serious potential
to impact on the native fish fauna (Vitule et al. 2006). For example, escape from ponds built
for recreational angling into the Guaraguaçu River basin in Paraná State, Brazil, resulted in
predation on endemic species.
In Thailand, C. gariepiunus was introduced as a farm fish, but in the areas where it is
reared (marshes and swamps) it competes with the native Clarias batrachus, the walking
catfish, the numbers of which have declined since the introduction of C. gariepinus. Another
possible reason for the decline may be hybridization between the two species reducing
genetic variation of C. batrachus (Na-Nakorn 1999).
Hybrid catfish fry are susceptible to certain pathogens, particularly Protozoa,
Monogenea, immature Digenea (metacercaria) on the gills, and bacteria (AAHRI 1995). High
mortalities caused by jaundice disease have been recorded in farmed hybrid Clarias
macrocephalus x C. gariepinus in Thailand (Pearson et al. 2004). Those affected display
symptoms of being lethargic and anorexic, with yellow pigmentation of the skin and gills.
Internally, the spleen, kidney and gall bladder are enlarged, and the spleen, kidney, liver and
body fat are a pale yellow colour. Consequently, fish farmers face an economic loss,
although some disease problems may be associated with inadequate farm management
practices. Another impact of the farming of C. gariepiunus is the effect of fish-farm waste,
including feed and faecal matter, on the surrounding ecosystem.
•
•
•
Good organoleptic qualities
High tolerance to poor environment conditions
Ease of breeding in aquaculture
References
AAHRI Newsletter Article (1995) Handbook of Hybrid Catfish: Husbandry and Health.
Cambray J.A. (2003) The need for research and monitoring on the impacts of tanslocated sharptooth
catfish, Clarias gariepinus, in South Africa. African Journal of Aquatic Science 28 191-195.
Na-Nakorn U. (1999) Genetic factors in fish production: a case study of the catfish Clarias. In: S.
Mustafa (ed.) Genetics in sustainable fisheries management. Fishing New Books, pp 175-187.
Pearson M.D., Chinabut S. Karnchanakharn S. & Somsiri T. (1994) Jaundice disease in the farmed
catfish hybrid, Clarias macrophalus x C. gariepinus, in Thailand. Journal of Fish Diseases 17,
325-336.
Petr T. & Swar S.B. (Editors) (2002) Coldwater fisheries in the trans-Himalayan countries. FAO
Fisheries Technical Paper 431, ?? pp.
Skelton P. (1993) A Complete Guide to the Freshwater Fishes of Southern Africa. Southern Book
Publishers Ltd,.
Teugels G. (1986) A systematic revision of the African species of the genus Clarias (Pisces:
Clariidae). Annales Musee Royal de l’Afrique Centrale 247, 1-199.
Vitule J., Umbria S. & Aranha J. (2006) Introduction of the African Catfish Clarias gariepinus into
Southern Brasil. Biological Invasions, 8, 677-681.
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Species name:Northern whitefish, Peled
Scientific name: Coregonus peled
(Gmelin, 1789)
Family Name: Salmonidae
Subfamily:
Coregoninae
Fig. 1
Peleds in aquarium in Kotka
Maretarium, Finland
Diagnostic Features
Northern whitefish Coregonus peled has a silvery colour and a higher, more bream-like
habitus than native European whitefish Coregonus lavaretus. In contrast to other large
coregonids, the lower jaw of peled is longer than the upper one. The number of gill rakers is
high, usually 50 – 65. Peled has a short lifespan. The maximum age is typically 4 - 6 years.
Age over 10 years is very exceptional. In northern Europe peled can reach weights of 1 – 2
kg.
Peled is native to arctic Russia from river Mezen in White Sea area to river Kolyma in
eastern Siberia. The species has been introduced to several European countries. Transfers
to the following countries in the EU territory have been reported (Elvira 2001, FAO 1997,
IUCN and UNEP web sites).
Belgium
Bulgaria
Czech Republic
Denmark
Estonia
Finland
France
Germany
Hungary
Latvia
Lithuania
Poland
Romania
Slovakia
Introductions are also reported to Former Yugoslavia, Ukraine, Uzbekistan, European part of
Russia, Serbia and Montenegro, Japan and China. It is likely, that all translocations have not
been recorded.
Introductions of peled have in many cases been intended for fisheries management in
special habitats like reservoir lakes, Butgenbach and Robertville in Belgium, Lokka and
Porttipahta in Finland (Albrouck & al. 2005, Sutela & al. 2004).
Habitat and Biology
In its native environment Coregonus peled has many ecological forms, demersal and
anadromous. Peled occurs in clear and cool, usually oligotrophic water bodies. C. peled
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tolerates slightly higher temperatures than C. lavaretus . Upper lethal temperature exeeds 25
°C, optimum for growth is around 20 °C. The species can tolerate slightly acidic conditions.
Peled´s main food is zooplankton. During the growing season the species swims near
the water surface and filtrates feed organisms. During stratification this behavior helps to
avoid low oxygen contents in deeper water.
The spawning time of peled in the autumn depends on local climate. In its native
habitats Peled spawns usually in November – December in rivers or shallow shore zones in
lakes on sand or gravel bottoms. The fry hatch during breaking up of ice cover. In finnish
hatcheries the peled spawns later than local coregonids. Peled eggs need less day-degrees
from fertilization to hatch than eggs of C. lavaretus in similar temperatures in Taivalkoski
hatchery, 185-195 versus 200-225 d°. (Määttä 2008).
In the Belgian reservoir lakes the C. peled uses narrower diet spectrum than C.
lavaretus. (Albrouck & al. 2005).
Aquaculture
Reliable information of the aquaculture production of Peled is not available, because only few
countries give separate figures for Peled in FAO aquaculture statistics. Generally only total
production of coregonids is reported. The global production of non-specified whitefish
species has shown steady increase from 1.068 tons in 1996 to 4.620 tons in 2005. (FAO
2007).
Peled fry or fingerlings are cultivated for stock enhancement in many of the countries,
where the species has been introduced.
In Belgium the reservoir lakes seem to meet the habitat requirements of C. peled in terms of
growth capacities and diet composition. On the other hand, the conditions necessary for the
natural reproduction of these two species do not seem to be totally fulfilled.
In Finnish reservoir lakes the reproduction of Peled has in some years been
successful resulting strong year classes (Sutela & al. 2004). In contrast, even repeated
releases of Peled to natural lakes have not resulted reproducing populations.
According to Swedish authorities a weak population of Coregonus peled in lake
Storvindeln in northern Sweden is threatened due to competition with indigenous species.
No reports of new species-specific diseases or special sensitivity to existing diseases
are available. According to finnish hatchery managers peled is easy to cultivate. (Määttä
2008).
In spite of abundant introductions of Coregonus peled to the western Europe no clear
adverse ecological or genetic effects are reported. The species seems to be a weak
competitor in its new habitats. In its original distribution area the species is adapted to
extremely continental arctic climate and oxygen-rich, oligotrophic and cool waters. The
climatic and trophic conditions in Western Europe do not adequately match the requirements
of Coregonus peled.
References
Albrouck, C M, Ergen, P M and Icha, J C M. (2005) Growth and diet of introduced coregonid fish
Coregonus peled (Gmelin) and Coregonus lavaretus (L.) in two Belgian reservoir lakes.
Applied ecology and environmental research 4(1), 27-44
Elvira B. (2001) Identification of non-native freshwater fishes established in Europe and assessment of
their potential threats to the biological diversity. Council of Europe, Convention ot the
conservation of European wildlife and natural habitats, Report T-PVS (2001)6.
FAO (2007) FAO Fishery statistics, Aquaculture production. FAO Yearbook Vol 100/2. FAO, Rome.
FAO (1997) FAO database on introduced aquatic species. FAO Database on Introduced Aquatic
Species. FAO, Rome.
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Määttä, V (2008) Oral communication.
Sutela, T, Mutenia, A and Salonen E (2004) Density of 0+ peled (Coregonus peled) and whitefish
(Coregonus lavaretus) in late summer trawling as an indicator for their year class strength in
two boreal reservoirs. Ann. Zool. Fennici 41, 255-262.
Fiskeriverket, Swedish national board of fisheries (2007) Storskallesik (Coregonus peled)
www.fiskeriverket.se
IUCN, The world conservation union (2007) The red list of threatened species, Coregonus peled.
www.iucnredlist.org.
RKTL Finnish game and fisheries research institute (2007) Kala-atlas, peledsiika (Coregonus peled)
www.rktl.fi (in Finnish).
UNEP-WCMC (2007) Species database, Coregonus peled, www.unep-wcmc.org
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ALIEN SPECIES SHEET
Species name: Channel catfish
Scientific name: Ictalurus punctatus (Rafinesque)
Family name: Ictaluridae
Diagnostic features
The channel catfish (Ictalurus punctatus) is blue-olive, grey or black on the upper part of the
body, usually with dark spots along the flanks and a white ventral surface. Like most
catfishes, the channel catfish has eight long and unequal feelers around its mouth and has
an adipose fin, similar to that found in salmon. It is stout bodied with a broad flattened head
and the mouth is large and terminal. The body is scale-less and slimy. It is liberally spotted
and has a deeply forked tail. Adults can grow to around 76 cm and a weight of up to 2 kg.
This species is migratory, ascending small streams to spawn, but at other times favouring
deeper, larger rivers or lakes with clear water and clean sandy or gravely substrates. The
species is easily confused with other North American ictalurids especially American catfish or
black bullhead (I. melas) and the brown bullhead (I. nebulosus) which are similar in size and
appearance.
The channel catfish is native to North America and southern Canada but was widely
imported to Europe in the nineteenth century, and has subsequently been introduced to
numerous countries across the globe (Fig. 2). It is now established in France, Holland,
Belgium and Germany, and also widespread in the Danube, having established selfsustaining populations in a number of Eastern European countries including Bulgaria, Italy,
Spain, Hungary, Romania Belarus and Russia. They have reportedly become pests in some
parts of southern Europe. The fish prefers still waters or slow flowing rivers with warmer
water and weed cover.
Habitat and biology
The channel catfish preferentially inhabits clean and well-oxygenated rivers and streams, but
can also be found in stillwaters. Ictalurid catfish have a wide and varied diet and are said to
be voracious feeders. Channel catfish feed primarily upon small fishes, crustaceans (e.g.
crayfish), mussels and snails, but may also consume aquatic insects and small mammals.
Channel catfish can attain lengths of up to 130 cm, and maximum weights of more than 26
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kg. Growth can be rapid in suitable conditions. The maximum life span is thought to be 16
years.
Endemic
Introduced
Figure 2. Distribution of Ictalurus punctatus worldwide
Ictalurus punctatus become sexually mature in 2-8 years and spawn once annually (Scott &
Crossman 1973; Moyle 1976), usually in summer. Fish may travel hundreds of kilometers
upstream or downstream in rivers to spawn (Becker 1983). The eggs are laid in a nest
excavated by the female. The nest is situated among stones, logs or other cover. Males
guard and fan water over nest during incubation, which takes 5-10 days, and stay with young
after hatching. Schools of young may persist several weeks after departure from nest. The
fry stay in a tight shoal for the first few days of life. Warm water, in the range 21-29oC, is
required for successful spawning. This is likely to limit, but may not preclude, successful
spawning in the northern Europe.
Fish production
Global aquaculture production of channel catfish has steadily increased from <150 000 t y-1
in the late 1980s to almost 400 000 t in 2005 (Fig. 3). Production is dominated by the USA
(mean >260 000 t y-1, 1995-2005), with China also increasing its production in recent years
(101 096 t in 2005), but culture in Europe is low (326 t in 2005). Capture fishery production is
low, with only the USA (508 t in 2005) and Bulgaria (8 t in 2005) exploiting the species.
There is very little information on which to make an assessment of the likely impact of this
species under European conditions. Possible impacts on local fish populations and the
aquatic environment might include:
•
•
•
•
direct predation on other fish.
adverse effects on the environment (e.g. effects on community structure).
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2500
Global
Europe
2000
300
1500
200
1000
100
500
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
0
1985
0
European production (t)
Global production (t x 1000)
400
Year
Figure 3. Trends in the aquaculture production of channel catfish. Note the different y-axis for global
and European production.
•
•
•
Catfish can occupy a range of habitat types and appear reasonably tolerant to
environmental conditions;
The relatively cool climate in northern Europe is unlikely to be suitable for these catfish,
which can be regarded as a warm water species. The species is therefore unlikely to be a
successful coloniser in northern countries, although it may be capable of spawning in
lower latitude countries, at least in warmer summers. It has, however, successfully
colonised in southern and eastern European countries;
May be regarded as a valuable sporting fish and could be subject to illegal transfer
between waters.
References
Bailey R.M. &Harrison H.M., Jr. (1948) Food habits of the southern channel catfish, Ictalurus lacustris
punctatus, in the Des Moines River, Iowa. Transactions of the American Fisheries Society
75,110-138.
Becker G.C. (1983) Fishes of Wisconsin. Univ. Wisconsin Press, Madison. 1052 pp.
Lever C. (1977) The naturalised animals of the British Isles. Hutchinson, London, 600 pp.
Lundberg J.G. (1992) The phylogeny of ictalurid catfishes: a synthesis of recent work. In R.L. Mayden,
(ed.) Systematics, historical ecology, and North American freshwater fishes. Stanford Univ.
Press, Stanford, Calfiornia, pp. 392-420.
Maitland P.S. & Campbell R.N. (1992) Freshwater fishes of the British Isles. HarperCollins, 368 pp.
Marsh P.C. & Brooks J.E. (1989) Predation by ictalurid catfishes as a deterrent to re-establishment of
hatchery-reared razorback suckers. Southwestern Naturalist 34, 188-195.
Moyle P.B. (1976). Inland fishes of California. University of California Press, Berkeley, 405 pp.
Phillips R. & Rix M. (1985) A guide to the freshwater fish of Britain, Ireland and Europe. Treasure
Press, 144pp.
Scott W. B. & Crossman E.J. (1973) Freshwater fishes of Canada. Fisheries Research Board of
Canada, Bulletin 184, 966 pp.
Townsend C.R. & Winterbourn M.J. (1992) Assessment of the environmental risk posed by an exotic
fish: the proposed introduction of channel catfish (Ictalurus punctatus) to New Zealand.
Conservation Biology 6, 273-282.
Wheeler A. (1978) Ictalurus melas (Rafinesque, 1820) and I. nebulosus (Lesueur, 1819): the North
American catfishes in Europe. Journal of Fish Biology 12, 435-439.
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Species name: Barramundi
Scientific name: Lates calcarifer (Bloch, 1790)
Family name: Centropomidae
Diagnostic features
The body is elongate and compressed, with a deep caudal peduncle. The head is pointed,
with a concave dorsal profile becoming convex in front of dorsal fin. The mouth is large with a
slightly oblique, upper jaw reaching to behind eye. The teeth are villiform; there are no
canines present. The lower edge of pre-operculum has a strong spine and operculum with a
small spine. There is a serrated flap above the origin of the lateral line. The lower first gill
arch has 16 to 17 gillrakers. The scales are large and ctenoid. The dorsal fin has 7 to 9
spines and 10 to 11 soft rays; a very deep notch almost divides the spiny from the soft part of
fin. The pectoral fin is short and rounded, with several short, strong serrations above its
base. The dorsal and anal fins both have scaly sheaths. The anal fin is rounded, with 3
spines and 7 to 8 short rays. The caudal fin is also rounded. Colour is either olive brown
above with silver sides and belly (usually juveniles) or green/blue above and silver below. No
spots or bars are present on fins or body.
Lates calcarifer, known as seabass in Asia and barramundi in Australia, is a large, euryhaline
member of the family Centropomidae that is widely distributed in the Indo-West Pacific region
from the Arabian Gulf to China, Taiwan Province of China, Papua New Guinea and northern
Australia (Fig. 2). Aquaculture of this species commenced in the 1970s in Thailand, and
rapidly spread throughout much of Southeast Asia.
Habitat and biology
Barramundi inhabits freshwater, brackish and marine habitats including streams, lakes,
billabongs, estuaries and coastal waters. Barramundi is an opportunistic predator; Crustacea
and fish predominate in the diet of adults.
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Figure 2. Distribution of barramundi comprising East Indian Ocean and Western central
Pacific. Japanese Sea, Torres Strait or the coast of New Guinea and Darwin, Northern
Territory, Queensland (Australia). Also, westward to East Africa. (source: www.fao.org)
Spawning seasonality varies within the range of this species. Barramundi in northern
Australia spawn between September and March, with latitudinal variation in spawning
season, presumably in response to varying water temperatures. In the Philippines
barramundi spawn from late June to late October, while in Thailand spawning is associated
with the monsoon season, with two peaks during the northeast monsoon (August – October)
and the southwest monsoon (February – June). Spawning occurs near river mouths, in the
lower reaches of estuaries, or around coastal headlands. Barramundi spawn after the full and
new moons during the spawning season, and spawning activity is usually associated with
incoming tides that apparently assist transport of eggs and larvae into the estuary.
Barramundi are highly fecund; a single female (120 cm TL) may produce 30–40
million eggs. Consequently, only small numbers of broodstock are necessary to provide
adequate numbers of larvae for large-scale hatchery production.
Larvae recruit into estuarine nursery swamps where they remain for several months
before they move out into the freshwater reaches of coastal rivers and creeks. Juvenile
barramundi remain in freshwater habitats until they are three–four years of age (60–70 cm
TL) when they reach sexual maturity as males, and then move downstream during the
breeding season to participate in spawning. Because barramundi are euryhaline, they can be
cultured in a range of salinities, from fresh to seawater. When they are six–eight years old
(85–100 cm TL), Australian barramundi change sex to female and remain female for the rest
of their lives. Sex change in Asian populations of this species is less well defined and primary
females
are
common.
Although some barramundi have been recorded as undertaking extensive movements
between river systems, most of them remain in their original river system and move only
short distances. This limited exchange of individuals between river systems is one factor that
has contributed to the development of genetically distinct groups of barramundi in northern
Australia, where there are six recognised genetic strains in Queensland, and a further ten in
the Northern Territory and Western Australia.
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Production
Global capture harvest of barramundi has increased steadily since the mid 1980s and
peaked at a little over 75,000 t in the early 21st Century but falling to about 60,000 t in 2005
(Figure 3). Catch is dominated by Indonesia, with marginal contributions from Malaysia and
Australia. The species supports important recreational fisheries in Australia and is thus not
fished extensively for commercial purposes.
Aquaculture production is has grown
progressively since the mid 1980s and has reached 27,000 t. Indonesia, Malaysia and
Taiwan Province of China are also major producers. A limited production is carried out in
French overseas territories (about 6 t in 2005).
80000
Aquaculture
70000
Capture
Aquaculture (t )
60000
50000
40000
30000
20000
10000
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
0
Year
Figure 3. Trends in the capture fishery and aquaculture production of barramundi.
Among the attributes that make barramundi an ideal candidate for aquaculture are:
• it is a relatively hardy species that tolerates crowding and has wide physiological
tolerances;
• the high fecundity of female fish provides plenty of material for hatchery production of
seed;
• hatchery production of seed is relatively simple.;
• barramundi feed well on pelleted diets, and juveniles are easy to wean to pellets;
• barramundi grow rapidly, reaching a harvestable size (350 g – 3 kg) in six months to
two years.
Today barramundi is farmed throughout most of its native range, with most production in
Southeast Asia, generally from small coastal cage farms. Often these farms will culture a
mixture of species, including barramundi, groupers (Family Serranidae, Subfamily
Epinephelinae) and snappers (Family Lutjanidae).
Australia is experiencing the development of large-scale barramundi farms that reflect
the industrialized style of aquaculture seen in Europe. Where barramundi farming is
undertaken outside the tropics, recirculation production systems are often used (e.g. in
southern Australia and in the north-eastern United States of America).
Barramundi has been introduced for aquaculture purposes to Iran, Guam, French
Polynesia, the United States of America (Hawaii, Massachusetts) and Israel. Although
introduced for aquaculture into a number of other countries, the only countries that have
reported production to FAO so far are shown in Figure 2.
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Figure 3. Main producer countries of Barramundi (source: FAO)
While barramundi fingerlings are still collected from the wild in some parts of Asia, which
might pressure wild populations, most seed supply is now through hatchery production.
Hatchery production technology is well established throughout the culture range of this
species this has lead to reduced pressure upon wild stocks for broodstock as well as
fingerling supply.
With one or two exceptions (culture in recirculation systems in the USA and southern
Australia), this species is cultured in earthen ponds or in cages. While there are universal
issues relating to impacts with the culture of fish in cage systems wherein impacts derive
mainly from nutrient inputs from uneaten fish feed and fish wastes, there is little information
on the impacts of the culture of barramundi outside their native range.
A potential impact associated with the culture of fish in open systems (cages or ponds
draining into water sheds) is the risk of introduction of a disease causing organism to wild
barramundi or sympatric species. The FAO (www.fao.org) have identified numerous
pathogenic organisms of Barramundi (2 viral, 10 bacterial, 9 protozoan, with 6 others
comprising lice, fungi and trematodes). It would appear that fungal infections are most
prevalent in cold waters (less than about 22°C), and are equally common in fish reared in
fresh and salt water. The risk of transfer of disease causing organisms is reduced with the
use of closed aquaculture systems assuming adequate treatment of effluent (e.g. ozonation)
is carried out and that intermediate hosts (e.g. birds, snails) are excluded from the culture
system. However, the risk of disease within the culture system might be exacerbated within
closed systems.
Escapes of fish are unlikely from closed systems. However, if they do occur,
particularly in temperate or colder climates, ambient water temperature should provided a
certain degree of protection from expansion given that barramundi do not feed below 20ºC
and cannot survive below 13ºC.
•
Setting up of fish farms in new areas could allow escapes, especially form cages in open
waters.
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ALIEN SPECIES SHEET
THE BLACK CARP (MYLOPHARYNGODON PICEUS)
Species name:
Taxonomy
Black carp
Species: Mylopharyngodon piceus (Richardson, 1846)
Subfamily Squaliobarbinae
Family Cyprinidae
Superfamily Cyprinoidea
Order Cypriniformes
Figure 1 Species Mylopharyngodon piceus (Froese & Pauly, 2007)
Synonyms (after Manea, 1985): Leuciscus piceus, Richardson, 1845, p. 298; Leuciscus
aethiops, Basilewski, 1855, p. 233; Myloleucus aethiops, Gunther, 1873, p. 247;
Mylopharyngodon aethiops, Peters, 1880; Rendahl, 1928, p. 54; Nichols, 1943, p. 89;
Myloleuciscus atripinnis, Garman, 1912, p. 116; Leucisculus fuscus, Oshima, 1920, p. 129;
Mylopharyngodon fuscus, Reeves, 1927, p. 6; Mylopharyngodon piceus Lin, 1935, p. 412;
Berg, 1949, v. II, p. 537; Nikolskii, 1956, p. 130.
Diagnostic features
Concerning body shape, the black carp is likewise grass carp (Ctenopharyngodon idella) with
cilindric body (Oţel, 2007), with more or less circular body section, moderate lateral oblate
(Harka & Sallai, 2004), less compressed (Kottelat & Freyhof, 2007).
Both species are considered chinese carps, which are similar with common carp
(Cyprinus carpio) (different from chinese carps through 2 pairs of feelers, dorsal fin much
longer, pharyngeal teeth on 3 arrays (Oţel, 2007).
The black carp distinguish through features:
D III 7 (8), A III 8, Lateral line 41 - (6/4) - 42 (Manea, 1985), Lateral line 39 - (6/4) - 43 (Harka
& Sallai, 2004).
fter Manea, 1985, studied individuals had following features in percents: maximum
high 25,2 %, predorsal emptiness 49,9 %, prenatal emptiness 73,6 %, preventral one 50 %,
caudal peduncle 19,1 %, minimum high 12,9 %, pectoral fin 17, 4 %, ventral fin 16 %, basal
of dorsal fin 11, 2 %, basal of anal fin 10, 7%, the head 27,4 %, the snout 7,14 %, the eye
3,93 %. The mouth is terminal and the edges are near to the nostrils. The ventral are
inserted at small distance behind of anterior edge of dorsal insertion.
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The black carp is a massive species, with large scales, dark color, the dorsal color is
more intense, tending to be bronze color and the abdomen color is dirty white (Harka &
Sallai, 2004).
The black carp is different from grass carp by his darkness color of the body (also the
vernacular name an example) and the onolariform pharyngeal teeth (chew type, strong and
massive for crashing the shells, Kottelat & Freyhof, 2007), rounded and disposed on 1 or 2
arrays respecting the formulas 4-5, 4-1.4, 1.4-1.4, otherwise the grass carp, after Oţel, 2007,
follows the formulas 2.4-2.4, 2.5-2.5 or 3.5-3.5. Another difference between this two species
is the darker color of the fins compared with rest of the body, pectorals and ventral fins are
intense black (Manea, 1985). Also the 4 arrays of scales under the lateral line of black carp
and 5 arrays of scales of grass carp (Harka & Sallai, 2004).
Following Harka & Sallai, 2004, another distinctive character between these two species is
the form of nasal orifice – convex at grass carp and concave at black carp.
The black carp can be resembled with chub species, distinguished by insertion of ventral fins
before dorsal fin at chub species (Harka & Sallai, 2004).
The black carp is a strong fish with abundant mucus on tegument and darkish fins
(Constantin, 1985).
The native area of black carp is south – east Asia, the mouth rivers Amur and Xi Jiang
(Froese & Pauly, 2007; Kottelat & Freyhof, 2007), occurrence of the hydrologic system
Amur, Huang Ho, Red River and Jance rivers (Fig. 2) from where was colonized in many
countries (Harka & Sallai, 2004).
Figure 2 Native area (red points) of Mylopharyngodon piceus (black carp) species (Froese & Pauly,
2007)
From native area the species was introduced in Amu Darya (Turkmenistan) and possible in
Tone (Japan), the only places where the species create population of black carp trough
natural reproduction (Kottelat & Freyhof, 2007).
Regularly this species was accidental introduced mixed with other chinese plant feeder
species (grass carp, silver carp, and bighead carp), firstly in 15th century in India and Taiwan
(Harka & Sallai, 2004), and ulterior in other places of the world.
In Europe, was introduced first time in 1939, in USSR waters, European part. In
Hungary first time of introduced species was accidentally in 1963, the lack of interest to
reproduce this species in ponds, had induct the disappearance from fishery, later being
official introduced (Harka & Sallai, 2004).
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Actually in Hungary, the black carp appears next to grass carp in some natural area (triple
area of Cris rivers and other places) (Harka & Sallai, 2004).
The species was introduced from Asia in Europe by artificial ways and further, the
next generations were obtained also by artificial reproduction. These species introduced for
control of population of molluscan vectors of fish and human parasites. Commonly used to
remove Dreissena mussels that clog hydroelectic plants (Kottelat & Freyhof, 2007).
Although the black carp used in aquaculture was stocked in Danube, Dniestr, Dniepr, Don,
Kuban and Volga drainages (Kottelat & Freyhof, 2007).
It was introduced from Asia to South America (in Costa Rica), in 1979, with unknown
results (Manea, 1985), on the other hand, the expansion of the species in other areas of Asia
(Vietnam) had significant results.
The black carp, alongside of other 3 chinese carp species (grass carp, silver carp and
bighead carp) was naturalized in all water basins from southern and central part of former
USSR, even in Siberia water basins. The production of fish species increased with 15 – 50%;
however the plant and zooplankton feeder had the most significant values (Manea, 1985).
Actual, according to Froese & Pauly, 2007, the species was introduced for experiment
and aquaculture in more states of Europe (Ukraine, Bulgaria, Hungary, Armenia, Latvia,
Moldavia, Serbia, Muntenegru and in other countries such as Albania, Cehia, Slovakia,
Austria the situation is not established). In Central and North America, the species is found
accidental and escaped from experimental areas in USA, in Cuba and Panama it was
introduced for aquaculture, and in Mexico for natural reproduction but without success.
In Africa, (introduced in Maroc) and in other areas of Asia (native in Vietnam,
Thailand and maybe Malaysia, and introduced in Kazakhstan, Uzbekistan, Turkmenistan) for
aquaculture (Froese & Pauly, 2007).
Although, the commerce of black carp is restricted by law in Germany, and some
states reported adverse ecological impact in the same time with species introduction (Froese
& Pauly, 2007).
The black carp, it was one of introduced species of Romania, in 1960-1965 years, the
results were given by Nucet fishery research station and in 80’s by Danube Delta Institute –
Tulcea in Danube Delta, and the obtained results was not continued. In Romanian ihtiofauna
this species appears very rarely, because of incapacity of reproduction in natural
environment like in whole Europe. The native stocks from China and Russia are strongly
declined (Kottelat & Freyhof, 2007).
Habitat and biology
The black carp prefer the big rivers, lives in water body and floodplain. In floodplain area,
major river bed, black carp is proliferating. Aboard of major or minor river bed the black carp
is feeding (Harka & Sallai, 2004). The black carp is some of species which prefer clean water
and big concentration of oxygen, in lowland of rivers and lakes Kottelat & Freyhof, 2007).
The species is potamodromous and demersal (Riede, 2004), cleanly water, pH: 7, 5-8, 5,
deep water preferred 5-30 m. The favorable climate is subtropical, with temperature between
0-40 ºC, between 53°N - 15°N (Froese & Pauly, 2007). The adults are feeding mostly with
shells and snails, rare with aquatically insects and shellfish. The maximal age probable is to
15 years, very rare 20 years (Nico et. al., 2005).
The adults alimentation is almost exclusive been mollusks (Harka & Sallai, 2004), like
prefer ate alimentation of carp (Cyprinus carpio) from Danube Delta, which is quartered in
settled area by shell Dreissena, feeding exclusive with this shell (Oţel, 2007). That why the
carp is competitor at black carp alimentation, the carp been omnivorous, has various
alimentations, not just mollusks like black carp.
The publication of maximal size was 122 cm (IGFA, 2001) and 35 kg (Novikov et. al.,
2002), by Harka & Sallai, 2004 the sizes are 1 m length and 55 kg weight (in Yanze river),
but was found much bigger individuals, unofficial more than 200 kg, official 157 kg and 220 m
in China. In Hungary the national record of black carp is 28 cm and 2 kg, recorded in 2000
year (Harka & Sallai, 2004). First time spawning (usually 116-173 000 eggs by Harka &
Sallai, 2004) of black carp females at 6-11 years, females up to the adulthood later than
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males. Up to the adulthood at 100 m standard length and 15 kg weight at females and 90 m
standard length and 11 kg weight at males (Kottelat & Freyhof, 2007).
Nuptial males have breeding tubercles on head and dorsal fins (Froese & Pauly,
2007, Constantin, 1986). Usually, the adults migrate up to river and spawns in open waters,
in March-July, at 19-30 ºC water temperature (in native water at 26 - 30ºC, after Harka &
Sallai, 2004). Eggs are pelagic or semi pelagic and hatch while drifting downstream. If the
river flow is blocked or if available river stretches are too short, eggs can not drift for long
enough and fail to develop. Larvae settle into floodplain lakes and channels with little or no
current. Larvae feed on zooplankton, than on ostracods and aquatic insects. At about 12 cm
SL, juveniles starts to feed on small snails and clams; larger juveniles and adults feed almost
entirely on mollusks (Kottelat & Freyhof, 2007, Harka & Sallai, 2004).
The species do not appear in Red List of IUCN.
Production
Native stocks in Russia and China have declined sharply (Kottelat & Freyhof, 2007).
Global natural productions are low and insignificant, instead the aquaculture productions are
increased, mostly in native areas from China (Fig. 3) and also the benefits are substantial
(Fig. 4), according to FAO statistics. In most of the countries, where the black carp is
included in aquaculture activities, the quantities of this species are not reported, the species
being in experimental phase. Only in Taiwan there were reported significant quantities of
black carp, according to FAO.
Black carp aquaculture production - FAO statistics
350000
300000
) 250000
s
e
n
o
t( 200000
n
o
it
c150000
u
d
o
r 100000
P
China
Romania
Russian Federation
Taiwan Province of China
50000
0
Year
Figure 3.The black carp production (tones) in aquaculture at world level
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Black carp aquaculture value - FAO statistics
600000
)
s
r 500000
a
ll
o
d400000
S
U
d
n300000
a
s
u
o
h
t( 200000
e
lu
a100000
V
China
Romania
Russian Federation
Taiwan Province of China
0
Year
Figure 4. Production benefits (thousand of US dollars) of black carp in aquaculture
For the majority of cases no information exists or has been collected about the impacts
introducing of black carp, where impacts have been reported these are both adverse and
beneficial. The main benefits are derived from aquaculture production (the big size of species
and high grade of meat). The principle adverse effects relate to spread of diseases and
pathogens, and potential competition with indigenous fauna.
For diseases and pathogens have been reported from black carp:
1. Grass Carp Hemorrhagic Disease Reovirus Viral diseases: high mortality 30 – 60 % (Fijan,
1999).
The reported states that the disease is widespread in the southern regions of mainland China
and has cause severe, economically devastating losses for the largest aquaculture
production in the world and with a reported mortality rates of 50%-70% in yearlings (Mao et
al. 1988, citation by Froese & Pauly, 2007).
2. Enteritis (Bacterial infection) Bacterial diseases (Nico et. al. 2005) with
Aeromonas punctata (bacterium) – affect the black carp and grass carp.
The pathogens, which are possible carrying by black carp, are not different pathogen of
another chinese carps (grass carp, silver carp or bighead carp), that why the black carp is
not a threat from this point.
Trade restricted in Germany (Anl.3 BArtSchV). Several countries reported adverse ecological
impact after introduction (Froese & Pauly, 2007).
Feeding with molluscs, which are intermediary host for some parasite worms on fish
(tramatods), is a good benefit for introduction of the black carp (Constantin, 1986).
By Manea, 1985, the black carp is not competitor to the other fish alimentation, this species
feeding only with mollusks.
However, by Otel, 2007, the carp is competitor to the black carp, although the carp is
omnivorous prefer ate alimentation of carp is mollusks (especially Dreissena). Otherwise,
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biodiversity of mollusks from Danube Delta is quantitative and qualitative very abundant,
being enough space for both species.
Main issues
Trade restricted in Germany (Anl.3 BArtSchV). Several countries reported adverse ecological
impact after introduction. The black carp is recently introduced from Asia in other continents,
mostly accidental with other 3 chinese species (grass carp, silver carp or bighead carp).
Increased productions in native area (China), gustative quality of meat and biological
significance (feeding with molluscs, host for parasites worms – trematods, parasites at fish
and sometimes at human) are some of benefits of species introduction.
The limited work on the control of black carp probably arises because few studies
have examined the ecological effects of black carp, but also this species have positive
economic impact in China and Taiwan regions where it has been introduced through
aquaculture production.
More in depth studies are need to assess the ecological impacts of the species
introduction if accurate assessment of any potential impacts is to be quantified.
References
Constantin Ghe., 1985. Reproducerea artificială a lotului de Mylopharyngodon piceus (scoicar) din
fermele Deltei Dunării. Tema 206/1985. Referat anual 465 al I.C.P.P.D.D, Tulcea, 26p.
Constantin Ghe., 1986. Reproducerea artificială a lotului de Mylopharyngodon piceus (scoicar) din
fermele Deltei Dunării. Tema 206/1985. Referat anual 499 al I.C.P.P.D.D, Tulcea, 23p.
Fijan N., 1999. Spring viraemia of carp and other viral diseases and agents of warm-water fish. p.177244. In P.T.K. Woo and D.W. Bruno (eds.) Fish Diseases and Disorders, Vol. 3: Viral, Bacterial
and Fungal Infections. CAB Int'l.
Froese R. and D. Pauly. Editors. 2007.FishBase. World Wide Web electronic publication.
www.fishbase.org, version (10/2007).
Harka A., Sallai Z., 2004. Magyaroszag halfaunaja, Ed. Nimfea T.E., Szarvas, 296p.
IGFA, 2001. Database of IGFA angling records until 2001. IGFA, Fort Lauderdale, USA.
Kottelat M. & Freyhof J., 2007. Handbook of European freshwater. Kottelat, Cornol, Switzerland and
Freyhof, Berlin, Germany, ISBN 978-2-8399-0298-4, 646p.
Manea Ghe. I, 1985. Aclimatizarea de noi peşti şi alte organisme acvatice. Edit. Ceres, Bucureşti, pp
160.
Nelson J., 2006. Fishes of the world. Fourth Edition. Edit. John Wiley & Sons, Inc., ISBN-13: 978-0471-25031-9, 601 p.
Nico, L.G., J.D. Williams and H.L. Jelks, 2005. Black carp: biological synopsis and risk assessment of
an introduced fish. American Fisheries Society, Bethesda, Maryland, USA, 337 p.
Novikov, N.P., A.S. Sokolovsky, T.G. Sokolovskaya and Yu.M. Yakovlev., 2002. The fishes of
Primorye. Vladivostok, Far Eastern State Tech. Fish. Univ., 552 p (pp.105-106).
Oţel V., 2007. Atlasul peştilor din Rezervaţia Biosferei Delta Dunării, Editura Centrul de Informare
Tehnologică Delta Dunării, INCDDD, Tulcea, ISBN 978-973-88117-0-6, 481p.
Riede, K., 2004. Global register of migratory species - from global to regional scales. Final Report of
the R&D-Projekt 808 05 081. Federal Agency for Nature Conservation, Bonn, Germany. 329
p.
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ALIEN SPECIES SHEET
Species name: Coho salmon
Scientific name: Oncorhynchus kisutch (Walbaum)
Family name: Salmonidae
Sub-family: Salmoninae
The coho salmon belongs to the salmon family (Salmonidae), a group of freshwater fishes
widely distributed across the northern hemisphere.
Diagnostic features
The coho salmon is characterized by the presence of small black spots on the dorsal surface
and the upper lobe of the caudal fin, and the lack of dark pigment along the gum line of the
lower jaw. Fish in the sea are dark metallic blue or greenish on the dorsal surface, silvery on
the flanks, and white on the ventral surface. Sexually maturing coho develop a light pink or
rose shading along the belly and the males may show a slight arching of the back. During the
spawning season, the fish turn green on the dorsal surface, bright red on the flanks, and
often dark on the ventral surface, with females less brightly coloured than males. There are
9-13 soft rays in the dorsal fin and 12-17 in the anal fin.
The coho salmon is native to the North Pacific, from the Anadyr River in Russia south
towards Hokkaido, Japan, and from Point Hope in Alaska south to Chamalu Bay in Baja
California, Mexico. Coho salmon have also been introduced in all the Great Lakes, as well as
many other landlocked reservoirs throughout the United States. The species has also been
introduced to a number of European countries, including Latvia, Russia, the Netherlands,
Cyprus, Greece, Spain, Italy, Sweden, Austria and Montenegro.
Habitat and biology
Coho salmon occurs in marine and freshwater habitats, with adults returning to their natal
rivers to spawn. The young emerge in the spring and usually live in fresh water for 1-2 years
before migrating to the sea late March through July. Young often spend the first winter in offchannel sloughs. Some fish leave fresh water in the spring, spend summer in brackish
estuarine ponds and then migrate back into fresh water in the fall. Coho salmon live in the
salt water for one or two years before returning to spawn. Young fish in lakes and rivers
consume mainly insects whereas, at sea, smolts prey upon planktonic crustaceans, and
larger individuals consume jellyfish, squids and fishes. Adults may attain lengths of more
than 100 cm and weights of over 15 kg. The maximum reported age is 5 years.
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Fish production
Global aquaculture production of coho salmon increased from <10 000 t in 1985 to a peak of
>150 000 t in 2001, before falling to ~100 000 t/yr from 2002-2005 (Fig. 2). Since the early
1990s, aquaculture production has been dominated by Chile (mean >86 000 t/yr, 19952005), with Japan (10 546 t/yr, 1995-2005) and Canada (1665 t/yr, 1995-2005) the only other
countries farming the species in recent years. Production in North American has nearly
ceased – constrained by local opposition, lack of suitable sea farming sites and falling market
prices. Coho salmon stocks presently used in aquaculture were derived from government
hatchery programmes in the United States of America and Canada, but most countries now
rely on local sources. France and Spain cultured coho salmon in small amounts until the
early 1990s, but there has been no production in Europe since 1995. Capture fishery
production has gradually declined from >40 000 t/yr in the mid-1980s to <20 000 t/yr since
the late 1990s (Fig. 2). The capture fishery sector is dominated by the USA (72% of global
production, 1985-2005), with Canada (17%) and Russian (9%) the other countries exploiting
the species.
100
Aquaculture
Capture
80
150
60
100
40
50
Capture (t x 1000)
200
20
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
0
1985
0
Year
Figure 2. Global trends in the capture fishery and aquaculture production of coho salmon.
There is relatively little information upon which to make an assessment of the likely impacts
of this species under European conditions. The occasional specimen is caught in coastal
fisheries but the origin is unknown and the impact unmeasured. Possible impacts on local
fish populations and the aquatic environment could include:
•
•
•
•
direct predation.
introduction of exotic parasites or diseases.
hybridisation with native salmonids.
•
Aquaculture development is the most likely cause of further dispersal of Oncorhynchus
kisutch, although the species can now disperse naturally (e.g. to Netherlands from
France, 1982);
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•
•
•
•
highly regarded as a sporting fish with good organoleptic qualities, which could contribute
towards their dispersal, especially through illegal stocking.
good potential for aquaculture production targeting a more specialist market than rainbow
trout.
environmental conditions in temperate northern European countries suitable for spawning
and colonisation.
high quality spawning habitat is essential for natural reproduction.
References
Amori G, FM Angelici, S Frugis, G Gandolfi, R Groppali, B Lanza, G Relini & G Vicini., In: Minelli A, S Ruffo & S
La Posta (eds) Checklist delle specie della fauna italiana, 110 Calderini, Bologna, 83 p. (.)
Froese, R. and D. Pauly. Editors. 2003. FishBase. World Wide Web electronic publication. www.fishbase.org
Ida H. (1984) Salmonidae. In: H. Masuda; K. Amaoka; C. Araga; T. Uyeno; T. Yoshino (eds). The Fishes of the
Japanese Archipelago. Tokai. Univ. Press. 40 pp
Scott W.B. & Crossman E.J. (1973) Freshwater Fishes of Canada. Fisheries Research Board of Canada, Bulletin
184, 966 pp.
Svetovidov A.N. (1984) Salmonidae. In: P.J.P. Whitehead et al., (eds). Fishes of the North-eastern Atlantic and
the Mediterranean (FNAM). Unesco, Paris, vol. I: 373-385.
Wheeler A. (1978) Key to the Fishes of Northern Europe. A guide to the identification of more than 350 species.
Frederick Warne (Publishers) Ltd., London. 380 pp
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ALIEN SPECIES SHEET
Species name: Nile tilapia
Figure 1: Nile tilapia
Image courtesy M
Staissny - FISHBASE
Scientific name: Oreochromis niloticus (Linneaus)
Family Name: Cichlidae (Cichlids)
Subfamily: Pseudocrenilabrinae
Diagnostic features
Nile tilapia have large heads with a single nostril on each side, and deep, laterallycompressed bodies. The most distinguishing characteristic of the species is the presence of
regular vertical stripes throughout the depth of caudal fin. Sexually mature males have
enlarged jaws, which may cause the upper profile to become concave. During the spawning
season the pectoral, dorsal and caudal fins become reddish; the caudal fin with numerous
black bars. The spinous and soft ray parts of the elongated dorsal fin are continuous; there
are 16-17 spines and 11-15 soft rays. The anal fin has 3 spines and 10-11 soft rays. Nile
tilapia attain a maximum length of 60 cm, which corresponds to a weight of about 5 kg. The
maximum reported age is about 10 years.
The Nile tilapia is native to Africa, including the coastal rivers of Israel, the Nile from below
Albert Nile to the delta, Jebel Marra, the basin of Lake Chad, and the rivers Niger, Benue,
Volta, Gambia and Senegal (Fig. 2). The area occupied by the species extends from 8°S to
32°N and from sea level to 1830 m. Nile tilapia preferentially live in fresh water, although the
species is also found in brackish water, such as in the Nile Delta. It has been widely
introduced throughout the world for aquaculture and capture fisheries (Fig. 2), and many
strains now exist. China is the largest producer of Nile tilapia, although many Asian countries
grow the species in farms or exploit naturalised stocks.
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Introduced
Endemic
Figure 2. Distribution of Oreochromis niloticus worldwide.
Habitat and biology
Nile tilapia is a tropical species that prefers to live in shallow water. The lower and upper
lethal temperatures for Nile tilapia are 11-12°C and 42°C, respectively, while the preferred
temperature ranges from 31 to 36°C. It is an omnivorous grazer that feeds on phytoplankton,
periphyton, aquatic plants, small invertebrates, benthic fauna and detritus, but has been
known to eat invertebrates and small-sized fish. As with other tilapias however, opportunism
in feeding is common. Nile tilapia can filter feed by entrapping suspended particles, including
phytoplankton and bacteria, on mucous in the buccal cavity, although its main source of
nutrition is obtained by surface grazing on periphyton mats. Sexual maturity in ponds is
reached at an age of 5-6 months at a total length of 6-10cm in the female, and 7-13cm in the
male. Spawning begins when the water temperature reaches 24°C. The breeding process
starts when the male establishes a territory, digs a craterlike spawning nest and guards his
territory. The ripe female spawns in the nest, and immediately after fertilization by the male,
collects the eggs into her mouth and moves off. The female incubates the eggs in her mouth
and broods the fry after hatching until the yolk sac is absorbed. Incubating and brooding is
accomplished in 1 to 2 weeks, depending on temperature. . Further batches are laid at
intervals (usually 30 to 40 days) and these are fertilised by the same or different males. The
number of eggs laid in a single spawning differs with the size of the female but ranges from
50 –1700.
Fish production
Worldwide aquaculture production of Nile tilapia has expanded from 233 601 t in 1990 to
1 703 125 t in 2005 (Fig. 3). By contrast, aquaculture production in Europe (the Netherlands
and Switzerland) only began in 2004 and is minimal (355 t in 2004 and 407 t in 2005). The
uncontrolled breeding of tilapia in ponds, which leads to excessive recruitment, stunting and
a low percentage of marketable-sized fish, dampened the initial enthusiasm for tilapia as a
food fish. However, the development of hormonal sex-reversal techniques in the 1970s
represented a major breakthrough that allowed male monosex populations to be raised to
uniform, marketable sizes. Capture fisheries also make a significant contribution to Nile
tilapia production worldwide, although not in Europe (Fig. 3). This production is largely from
stocked systems, especially reservoirs and ponds in tropical countries across the world.
Major problems exist in fisheries where the species has successfully established. This is
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usually because of the propensity for Nile tilapia to breed and produce many offspring,
reducing the capacity for growth.
Production (tonnes x 1000)
2000
Global
Capture
1500
1000
500
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
0
Year
Figure 3. Trends in capture fishery and global aquaculture production of Oreochromis niloticus.
Generally, there is relatively little information on which to make an assessment of the likely
impacts of this species under European conditions, but O. niloticus has been widely
classified as a pest where introduced (Welcomme 1984). In semi-tropical and tropical
climates the species has established self-maintaining populations in a variety of habitats, and
has proved difficult to eradicate.
Possible impacts on local fish populations and the aquatic environment may include:
•
•
•
•
•
direct predation.
hybridisation with native species.
adverse effects on the environment through habitat destruction (vegetation removal).
•
•
•
Nile tilapia is one of the most successful and prolific fish in a wide variety of water types.
It is capable of utilising a range of habitat types, with a preference for eutrophic, turbid
waters of shallow mean depth.
it is very resistant to low dissolved oxygen, tolerating values as low as 0.1 ppm, which is
a common characteristic of all tilapias.
it is able to live and reproduce at a wide range of temperatures, between 13 and 37°C,
although the optimum for feeding, growth and spawning is between 20 and 32°C. This
means it is unlikely that the species will be able to spawn in the majority of waters in
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•
•
•
northern Europe, but it could establish in Mediterranean climates. Warm water
discharges from power stations may increase the chance of viable populations becoming
established.
the species is euryhaline, surviving in salinities higher than 30‰ in some East African
coastal rivers. Studies have demonstrated that tilapine cichlids are capable of
successfully spawning in 100% seawater, which means they are pre-adpated for
dispersal via seawater.
highly regarded as an aquaculture species because of its ease of culture and high
survival in poor conditions.
prolific breeding capabilities, both in terms of age at first maturity and ability to repeat
spawn with weeks if conditions are suitable.
References
Bluhdorn, D. R.; Arthington, A. H.; Mather, P. B. 1990. The introduced cichlid, Oreochromis
mossambicus, in Australia: A review of distribution, population genetics, ecology,
management issues and research priorities. In: Australian Society for Fish Biology Workshop.
Introduced and Translocated Fishes and Their Ecological Effects. Pollard, D. A. (ed.) no. 8,
pp. 83-92.
Chervinski, J. 1986. Identification of additional Tilapia from Lake Kinneret, Israel, by the form of their
scales. Aquaculture, 55. 157-159
Fishelson, L. 1983. Social behaviour of adult tilapia fish in nature and in captivity (Israel). In:
Proceedings of the International Symposium on Tilapia in Aquaculture, Nazareth, Israel, 8-13
May. Fishelson, L.; Yaron, Z., pp.48-58.
Hauser, W.J. 1977. Temperature requirements of Tilapia zillii. Calif. Fish. Game, 63 (4), 228-233.
Platt, S. and Hauser, W. J. 1978. Optimum temperature for feeding and growth of Tilapia zillii. Prog.
Fish. Cult. 40 (3), 105-107.
Shireman, J. V. 1984. Control of aquatic weeds with Exotic Fishes. . In: Distribution, Biology, and
Management of Exotic Fishes. W. R. Courtenay, Jr. and J. R. Stauffer, Jr. (eds.) The John
Hopkins University Press.
Trewavas, E. 1983. Tilapiine Fishes of the genera Sarotherodon, Oreochromis and Danakilia. British
Museum (Natural History).
Welcomme R.L. (1984) International Transfers of Inland Fish species. In: Distribution, Biology, and
Management of Exotic Fishes. W. R. Courtenay, Jr. and J. R. Stauffer, Jr. (eds.) The John
Hopkins University Press.
Wheeler, A. and Maitland, P. S. 1973. The scarcer freshwater fishes of the British Isles. I. Introduced
species. J. Fish. Biol. 5, 49-68.
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ALIEN SPECIES SHEET
Species name: American paddlefish
Mississippi paddlefish
Scientific name: Polyodon spathula (Walbaum)
Family name: Polyodontidae
Order (Acipenseroiformes) - the sturgeons
Diagnostic features
The paddlefish is characterised by its paddle-like snout and differs from the sturgeons
because of the lack of large body scales (or scutes). The skin of the American paddlefish is
bare except for a few vestigial scales, the head is drawn out at the front into a flattened
snout. The snout is between 1/3 & 1/2 of the total length of the fish. There are minute barbels
on the snout. The function of the snout is not entirely clear, possibly being used to stir up the
mud to release food items, although others suggest it is a sensory organ. Colouration of the
American paddlefish is variable: slate grey, bluish-grey, or purplish dark blue.
The gill covers are large and triangular, with the apex to the rear, and are drawn out into a
point. The pectoral and pelvic fins are medium sized; the medium sized dorsal fin is set well
back on the body with the anal fin opposite it.
The American paddlefish is native to North America, namely the Mississippi River system,
including the Missouri River, the Ohio River, the Oklahoma River, and their major tributaries.
The species has been introduced to Poland, the Ukraine, Bulgaria, Serbia, Moldova,
Romania, Russia, Hungary, China, Austria and Germany.
Habitat and biology
The paddlefish inhabits the slow-flowing reaches of large rivers, usually in water deeper than
1.3 m. American paddlefish possess numerous long gill rakers and are primarily filter
feeders, principally consuming zooplankton. However, they also consume a variety of benthic
items including crustaceans and worms, which are probably detected using its long snout.
There are some reports of fish being recorded in the diet (e.g. shad have been found in their
stomachs).Paddlefish may attain lengths of over 220 cm, and maximum weights of over 90
kg. The maximum reported age is 55 years.
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Figure 2. Native range of American paddle fish
http://www.umesc.usgs.gov/aquatic/fish/paddlefish/faq.html
Polyodon
spathula
(from
USGS
-
Paddlefish is an important species for caviar. Females take up to 10 years to mature, at
about 1 m long, and males 7 years to mature at a slightly smaller size. Eggs are greenish
black in colour and 2-3 mm in diameter; as they are laid they sink and stick to pebbles on the
bottom. Each female is capable of producing over one-half million eggs a year, but they may
not spawn every year. Larvae begin to grow their eyes and barbels within a few hours of
hatching, the paddle begins to grow after 2 to 3 weeks. Growth rates in captivity are 15 to 30
cm a year.
Paddlefish were once very abundant in most central U.S. river systems, but populations have
declined greatly due to over harvesting, sedimentation, and river modification. One of the
major reasons for declining paddlefish numbers isdamming that has blocked paddlefish
migration routes. In May 2000, the Canadian Species at Risk Act listed the Paddlefish as
being extirpated in Canada. Reintroduction efforts for a species take many years to mature
enough fish to help the population reach mature breeding numbers.
Fish production
Aquaculture of paddlefish has been carried out in North America since 1915, but has been
more effective in recent years and is still considered in the development phase (Mims 2001,
Hubenova et al. 2007), with no commercial production at present. The Missouri Dept. of
Conservation has implemented a programme of culturing and restocking paddlefish. The
U.S. fish and wildlife service has adopted a guidance document “Framework for the
management and conservation of paddlefish and sturgeon species in the United States”.
Capture fishery production of paddlefish, represented entirely by the USA, ranged from 161 t
in 1966 to 898 t in 1982 (mean ~400 t y-1, 1950-1987), but ceased in 1988.
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There is very little information on which to make an assessment of the likely impact of these
species under European conditions. Possible impacts on local fish populations and the
aquatic environment might include:
• competition with indigenous fish for food cover or spawning sites;
• the introduction of new parasites or exotic diseases;
• adverse effects on the environment through habitat degradation (e.g. effects on benthos,
water turbidity changes due to feeding activity).
•
•
•
Spawning requirements include: increased water flow to initiate spawning, a water
temperature of 15 oC water and suitable gravel substrate for egg attachment (Dillard et
al., 1986).
Possible interest as both an ornamental species and for angling.
Possible long-term interest for caviar production.
References
Birstein V.J., Waldman J.R. & Bemis W.E. (1997) Sturgeon biodiversity and conservation. Kluwer
Academic Press, 444 pp.
Dillard J.G., Graham L..K. & Russell T.R. (editors) (1986) The Paddlefish: Status, Management and
Propagation. Modern Litho-Print Co.: Jefferson City, Missouri, 159 pp.
Hubenova T., Zaikov A. & Vasileva P. (2007) Management of paddlefish fry and juveniles in Bulgarian
conditions. Aquaculture International 15, 249-253.
Michaletz P.H. & Rabeni C.F. (1982) Feeding ecology and growth of young-of-the-year paddlefish in
hatchery ponds. Transactions of the American Fisheries Society 111, 700-709.
Mims S.D. (2001) Aquaculture of paddlefish in the United States. Aquatic Living Resources 14, 391398.
Nelson J.S. (1994) Fishes of the world. Third edition, John Wiley & Sons Ltd.
Petrocci C. (1994) Tails from the road: Paddlefish. Aquaculture magazine. 20 (3): 63 - 67.
Southall P.D. &Hubert W.A. (1984) Habitat use by adult paddlefish in the upper Mississippi River.
Transactions of the American Fisheries Society 113, 125 - 131.
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Species name:Brook trout
Brook charr
Scientific name: Salvelinus fontinalis
(Mitchill, 1814)
(Sub family – Salmoninae)
Figure 1. Brook trout
Image taken from:
http://fishing.hojusports.com/data/file/fish/4
6ac6e70_brooktrout.jpg
Diagnostic Features
Salvelinus fontinalis is characterised by a dorso-ventrally flattened body and terminal mouth.
The dorsal fin is located slightly forward of the pelvic fin and the adipose fin in located directly
above the anal fin. The number of dorsal spines ranges from III to IV, while there are 8-14
dorsal fin rays. The number of anal spines and rays also range between III – IV and 8-14,
respectively. The caudal fin has 19 rays and is slightly concave. The skin is generally green
to brown with a pale vermicular pattern, which is also found on the dorsal fin and sometimes
extends to the caudal; this is combined with pale and/or red spots that may be surrounded by
a ‘halo’ of blue. The pectoral, pelvic and anal fins all display a white leading edge and an
adjacent dark stripe, while the rest of the fins are red in colour. The species is similar in
shape to Arctic charr but the head is larger. Salvelinus fontinalis is anadromous with
reproducing individuals usually portraying a white underside with a dark green back; the
sides tend to be silvery and the spots become pale pink (McAllister et al. 1987). Brook trout
is known to hybridize with Arctic charr
Salvelinus fontinalis can reach lengths in excess of 80 cm, with the largest weighing
more than 9 kg (International Game Fish Association 1991). Brook trout typically have a
maximum age of approximately 7 years; although introduced specimens in California have
reached 15 years (McAfee 1966).
Brook trout is native to North America, East Canada (Newfoundland to Hudson Bay), the
South Atlantic, the Great Lakes and the Mississippi river basin. (Scott & Crossman 1973;
Figure 2). It was introduced into the United Kingdom from the USA in circa 1869-1871
(Welcomme 1988; Wheeler 1992). The species was originally intended for aquaculture and
has now been introduced to many temperate freshwater systems across Europe (Austria 1970; Belgium - 1980; Bulgaria - unknown; Czech Republic - 1930; Denmark - 1902; Finland
- 1965; France 1904-1977; Germany - 1890; Hungary - 1940; Italy - 1895; Lithuania unknown; Latvia - unknown; Poland - 1890; Romania - 1900; Serbia-Montenegro - unknown;
Slovakia - unknown; Spain - 1934; Switzerland - 1883; Sweden - 1872; Yugoslavia - 1892)
(Welcomme 1988). In Switzerland federal legislation has limited the introduction and
stocking of brook trout. Although this species was introduced to Portugal (1900s),
Netherlands, Cyprus (1971), Estonia (1896) and Greece (unknown) (Blanc et al. 1971;
Welcomme 1988; FAO 1997), it has not become established.
Brook trout has also been introduced globally to Alaska (unknown) (McAllister, 1987),
Argentina (1904), Australia (unknown), Bolivia (1948), Chile (unknown), Colombia – though
not established (1955) (Welcomme, 1988), Falkland Islands (Lever, 1996), Hawaii (1876)
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(Maciolek, 1984), Iran (unknown), Japan (1901), Kenya (1950), Kerguelen Islands (1992),
Mexico (unknown), Morocco (1941), New Zealand (1877-1987), Norway (1870), Papua New
Guinea (1974), Russia (before 1914), South Africa (1950), Venezuela (1937) and Zimbabwe
(1955). Again brook trout was originally introduced to these countries for aquaculture but the
species is now mainly used for sport and angling. In the Kerguelen Islands the stock is
continuously replenished by France as the ecosystem does not support the natural
reproduction of the species. Brook trout was introduced into Peru in 1955, but to fill and
ecological niche rather than for aquaculture or sport.
There is an extensive food market for brook trout (Morrow 1980) and it is extensively
used as an experimental animal (Scott & Crossman 1973).
Introduced
Endemic
Figure 2. Map showing countries where brook trout are endemic and have been introduced.
Outline map from: http://www.egt.geog.uu.nl/docs/WORLDLEG.gif
Habitat and Biology
Brook trout occurs in well oxygenated, clear and cool creeks, rivers and lakes (Page & Burr
1991; Allen et al. 2002). In the USA and Canada, brook trout make upstream movements
during the spring, summer and autumn and downstream movements in the spring and
autumn. Some individuals run to the sea when stream temperatures rise in spring. These
individuals may remain at sea for up to three months, but do not move more than a kilometre
from the river mouth (White 1941; Smith & Saunders 1958). The species can tolerate slightly
acidic conditions (pH 5.5-4.0) and prefers oligotrophic water bodies. Brook trout is demersal
and lives in water depths ranging from 15 – 27 m and is usually found in temperate waters of
between 0 – 25 °C.
Brook trout feed on a wide range of organisms, including crustaceans, worms,
insects, molluscs, leeches, fish and amphibians and some small mammals. There is also
some evidence of consumption of plant material (Scott & Crossman 1973).
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Fish production
Global production of brook trout has increased
steadily since the mid 1980s and peaks at a little
over 1000 t in 2003, falling to about 800 t in 2005
(Figure 4). Production is dominated by
aquaculture in Europe with a few tonnes of fish
landed from open waters. The main producing
countries (figures given for 2005) are Austria
(246 t), Czech Republic (130 t), Denmark (206 t)
and Romania (152 t in 2004). Some small
production takes place in Bosnia (25 t), Bulgaria
(4 t), Slovakia (9 t) Slovenia (31 t) and the United
Kingdom (2 t). France was a major producer up
to 2001 (293 t) but there have been no records
since that time.
1200
1000
800
600
400
Figure 4. Trends in aquaculture production of brook
trout in Europe.
200
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
0
For the majority of cases no information exists or has been collected about the impacts
introducing brook trout; where impacts have been reported these are both adverse and
beneficial. The main benefits are derived from aquaculture production and improved sport
angling experience, both of which generate income and create employment, albeit on a local
scale.
The principle adverse effects relate to spread of diseases and pathogens, and
potential predation and competition with indigenous fauna. Four diseases or pathogens have
been reported from brook trout: whirling disease, enteric redmouth disease,
Hysterothylacium infection and Camallanus infection. Whirling disease is a parasitic infection
caused by Myxobolus cerebralis. It affects juvenile salmonids and causes neurological
damage and skeletal deformation. Brook trout and rainbow trout are the most heavily
affected by this pathogen. This pathogen can be found in much of the brook trout range and
therefore may causes adverse effects to both wild and cultured salmonids in these areas.
Enteric redmouth disease is caused by the bacteria Yersinia ruckeri, which causes
haemorrhaging to the skin, eyes, gill filaments, mouth and internal organs. Enteric redmouth
disease affects a large number of different species as well as salmonids. These may include
carp, burbot, catfish, eels, minnows, sole, sturgeon, turbot and whitefish. This means that the
introduction of fish carrying this disease may have a huge detrimental ecological impact on
local fish populations. Hysterothylacium infection is caused by a parasitic nematode
Hysterothylacium patagonense. This infection is mainly seen in Patagonia and Argentina. It
infects the digestive tracts of introduced species of fish including brook trout, and brown trout
and probably originates from temperate bass (Moravec et al. 1997). Camallanus infection is
also a parasitic infection caused by a nematode. This infection affects the stomach, and also
mainly affects trout species (CEFAS; http://www.lsc.usgs.gov/FHB/leaflets/82.asp).
Some evidence exists for increased predation pressure infauna and epifauna in river
systems where brook trout has been introduced, but these studies are inconclusive (Allan
1982; Bechara et al. 1993). Similarly there is evidence that brook trout compete with other
salmonids where they coexist, although brook trout are not always the dominant species, and
this may explain why the species has not successfully established in some countries / rivers.
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Brown trout (Salmo trutta), for example, appears to out compete brook trout for space,
leaving brook trout to inhabiting less favourable areas, although the feeding behaviour of
brook trout does not change with the removal of brown trout (Fausch & White 1981). It has
also been suggested that there is competition between brook trout and rainbow trout
(Oncorhyncus mykiss), although the mechanisms involved in this competition is widely
debated (Fausch 1988). There is also evidence that hatchery reared and released brook
trout are more aggressive than wild populations (Moyle 1969; Einum & Fleming 2001).
There is limited work on the control of brook trout probably arises because few
studies have examined the ecological effects of brook trout, but also this species has positive
economic impact in regions where it has been introduced through aquaculture production
and improved angling opportunity. More in depth studies are need to assess the ecological
impacts of the species introduction if accurate assessment of any potential impacts is to be
quantified.
•
•
•
Good potential for aquaculture production targeting a more specialist market than
rainbow trout.
Highly regarded as a sporting fish with good organoleptic qualities.
Environmental conditions in temperate northern European countries suitable for
spawning and colonisation. Populations become established in a suitable habitat, but
further colonisation of new reaches (if unaided by man) can be slow.
References
Allan J.D. (1982) The effect of reduction of trout density on the invertebrate community of a mountain stream.
Ecology 63, 1444-1455.
Allen G.R., Midgley S.H. & Allen M. (2002) Field Guide to Freshwater Fishes of Australia. Western Australian
Museum. Perth, Westeern Australia, 394 pp.
Bachara J.A., Moreau G. & Hare L. (1993) The impact of brook trout (Salvelinus fontinalis) on an experimental
stream benthic community: the role of spatial and size refugia. Journal of Animal Ecology 62, 451-464.
Blanc M., Gaudet J-L. & Hureau J-C. (1971) European Inland Water Fish. A Multilingual catalogue. Fishing News
(Books) Ltd. London.
Einum S. & Fleming I.A. (2001) Implications of stocking: ecological Interactions between wild and released
salmonids. Nordic Journal of Freshwater Research 75, 56-70.
FAO (1997) FAO database on introduced aquatic species. FAO Database on Introduced Aquatic Species. FAO,
Rome.
Fausch K.D. & White R.J. (1981) Competition between brook trout (Salvelinus fontinalis) and brown trout (Salmo
trutta) for positions in a Michigan stream. Can. J. Fish. Aquat. Sci. 38(10) 1220-1227
Fausch, K.D. (1988) Tests of competition between native and introduced salmonids in stream: What have we
learned? Canadian Journal of Fisheries and Aquatic Sciences 45, 2238-2246.
International Game Fish Association (1991) World Record Game Fishes. International Game Fish Association,
Florida. USA.
Lever C. (1996) Naturalised Fish of the World. Academic Press, California. USA, 408 pp.
Maciolek J.A. (1984) Exotic fishes in Hawaii and other Islands of Oceania. In: W.R. Courtenay Jr and J.R. Stauffer
Jr. (eds) Distribution, Biology and Management of Exotic Fishes . John Hopkins University Press,
Baltimore, pp. 131-161.
McAfee W.R. (1966) Eastern Brook Trout In: A Calhoun (ed.) Inland Fisheries Management. California
Department of Fish and Game. Sacramento, pp. 246-260.
McAllister D.E., Legendre V. & Hunter J.G. (1987) Liste de noms inuktitut (esquimaux), fançaise, anglaise et
scientifiques des poissons marin du Canada arctique. Rapp. Manus. Can. Sci. Halieut. Aquat. 1932, 106
pp.
Moravec F., Urawa S. & Coria C.O. (1997) Hysterothylacium patagonenses n. sp. (Nematoda: Aniskidae) from
freshwater fishes in Patagonia, Argentina, with a key to the species of Hysterothylacium in American
freshwater fishes. Systematic parasitological 36, 31-38.
Morrow J.E. (1980) The Freshwater Fishes of Alaska. University of B.C. Animal Resources Ecology Library, 248
pp.
Moyle P.B. (1969) Comparitive behaviour of young brook trout of domestic and wild origin. Progressive. Fish
Culturist 31, 51-56.
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Page L.M. & Burr B.M. (1991) A Field Guide to Freshwater Fishes of North America North of Mexico. Houghton
Mifflin Company, Boston, 432 pp.
Scott W.B. & Crossman E.J. (1973) Freshwater fishes of Canada. Bulletin of the Fisheries Research Board of
Canada, 184, 1026 pp.
Smith M.W. & Saunders J.W. (1958) Mpvements of the brook trout, Salvelinus fontinalis (Mitchill) between and
within fresh and salt water. Journal of the Fisheries Research Board of Canada 15, 1743-1761.
Welcomme R.L. (1988) International Introductions of inland aquatic species. FAO Fisheries Technical Paper 294,
318 pp.
Wheeler A. (1992) A list of the common and scientific names of fishes of the British Isles. Journal of Fish Biology
41, 1-37.
White H.C. (1941). Migration of sea-running Salvelinus fontinalis. Journal of the Fisheries Research Board of
Canada 5, 258-264.
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ALIEN SPECIES SHEET
Species name: Lake trout
Great Lake trout
American trout
Lake charr
Figure 1., FishBase, picture
(Sanam_u6.jpg) by E. Damstra
Scientific name: Salvelinus namaycush (Walbaum)
Sub-family: Salmoninae
The lake trout belongs to the salmon family (Salmonidae), a group of freshwater fishes
widely distributed across the northern hemisphere.
Diagnostic features
The lake trout resembles the European brown trout (Salmo trutta), although it tends to be
larger, often reaching 90 cm (7-8 kg) in size. The body shape is similar to that of the salmon,
except that the angle of the jaw reaches to well behind the eye. The species s characterized
by laterally flattened body, a broad head and a large, terminal mouth, with the snout usually
protruding slightly beyond the lower jaw when the mouth is closed. The dorsal fin is situated
slightly forward of the pelvic fin and the adipose fin is located directly above the anal fin and
the tail is deeply forked. The number of dorsal spines is 4 – 5 and dorsal soft rays 8 – 10.
The number of anal spines is 4 – 5 and anal soft rays 8 – 10 (Morrow 1980). Caudal fin with
19 rays (Spillman 1961). The number of vertebrae is 61 – 69. Lateral line slightly curved
anteriorly. The flanks and dorsal surface are usually dark greenish-brown or grey, with white
or yellowish spots, while the ventral surface is yellowish-white (Morrow 1980). The pectoral,
pelvic and anal fins are rose coloured with a white band on the edge, while the adipose fin is
tinged with orange, and the tail is deeply forked. Pale spots are present on dorsal, adipose
and caudal fins, and usually on the base of the anal fin. The dorsal and anal fins have 4-5
spines and 8-10 soft rays. At spawning time, males develop a dark lateral stripe and become
paler on the back (Morrow 1980).
Salvelinus namaycush is native to North America and was originally found throughout most
of Canada and Alaska (Fig. 2). In the Arctic, it is widely distributed in the Yukon and
Northwest territories and is established on some of the arctic islands including Victoria and
Banks islands. Populations were originally found in all of the Great Lakes, but are now extinct
in Lake Erie. The species has been introduced to locations around the world and elsewhere
in North America. It was first introduced into Europe into Finland, Switzerland and Sweden
where it is thriving in the deep, alpine lakes, but has subsequently been introduced into most
member states. Naturally reproducing stocks have also established in Germany, Argentina,
Japan, Italy, Norway and New Zealand (FishBase; Crossman 1995) (Fig. 3).
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Figure 2. Native distribution of lake trout in North America according to FishBase.
Introduced
Endemic
Figure 3. Map showing countries where lake trout are endemic and have been introduced.
Habitat and biology
The lake trout is found both in shallow and deep waters of northern lakes and streams, but is
restricted to relatively deep lakes in the southern part of its range (Scott & Crossman 1973).
In shallow water, they are easily caught by recreational fishers. In southern regimes, they
take refuge in the cooler temperatures below the thermocline, in summer months. Optimal
temperature for lake trout is 14–18 ºC and the lethal temperature 23.5 ºC (Nilsson &
Dahlström 1968). Although Lake trout is found in coastal waters it is less tolerant of saline
water than other charrs; the critical salinity is 11–13 ‰ (Boulva & Simard 1968). Lake trout
has a long lifespan and maximum reported age is 50 yr. The growth of lake trout varies
widely; in Canadian lakes they grow larger than 23 kg (Scott and Crossman 1973) but have
reached 46 kg in weight, 126 cm in length and of age 20–25 yr (Lake Athabasca; Scott &
Crossman 1973).
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Adult lake trout feed on a variety of organisms, such as freshwater sponges,
crustaceans, plankton, insects, fishes (with a preference for ciscoes) and small mammals,
while juveniles eat mainly insect larvae, Daphnia and Gammarus. The growth of lake trout is
initially slow but it increases as they start to feed on fish (Nilsson and Dahlström 1968), when
they are around 15 cm long. Adult lake trout have few predators, but are commonly used as
hosts for lampreys. The eggs, however, are more vulnerable and are eaten by round
whitefish and brown bullhead.
Spawning occurs during the autumn or early winter (September to November), when
the water temperature is between 8 and 14 °C. Specific habitats are selected for spawning,
typically close to the shore and in shallow (<2 m) water, over clean, coarse substrate, such
as gravel, but spawning can occur down to 90 m. Spawning occurs exclusively at night and,
in contrast to other salmonid species, lake trout do not build a redd but deposit their eggs
directly on the substrate. Large females produce approximately 2000 eggs per kg of body
weight. The eggs hatch the following spring, usually from March to April. Male lake trout
mature earlier than females, usually spawning from two years of age, while females first
spawn at the age of three years.
Lake trout has been known to hybridise in nature with the brook trout but such hybrids
are almost invariably reproductively sterile. Hybrids are also artificially propagated in
hatcheries and then planted into lakes in an effort to provide sport fishing opportunities.
Fish production
Capture fishery production, represented by Canada and the USA, has remained at 8001100 t y-1 since the early 1990s, with Canada the most significant producer (Fig. 2). There is
currently no aquaculture production of lake trout.
Production (t)
1500
USA
Canada
1000
500
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
0
Year
Figure 3. Trends in the global capture fishery of lake trout.
Lake trout have been introduced into Swedish lakes since 1959, and no harm to the native
fish populations has been demonstrated (Goenczi & Nilson 1983). Similarly, with the
exception of predation on whitefish, no interactions between lake trout and native species
have been recorded in the alpine lakes of Switzerland. Predator pressures exerted by lake
trout are, however, believed to have prevented stocked brook trout (Salvelinus fontinalis)
from establishing a self-sustaining population in Castle Lake, California. The introduction of
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lake trout to Lake Tahoe in New Zealand led to the demise of the native Lahontan cutthroat
Oncorhynchus clarki henshawi. Similarly, lake trout has replaced native cutthroats in deep
Rocky Mountain lakes and also bull trout in Flathead Lake, Montana, and Pend Orielle Lake,
Idaho.
There is relatively little information upon which to make an assessment of the likely
impacts of this species under European conditions. Possible impacts on local fish
populations and the aquatic environment could include:
•
•
•
•
direct predation (e.g. on whitefish).
hybridisation with native salmonids.
•
•
•
•
•
Highly regarded as a sporting fish with good organoleptic qualities and this could
contribute towards their dispersal, especially through illegal stocking.
Good potential for aquaculture production targeting a more specialist market than
rainbow trout.
Environmental conditions in temperate northern European countries suitable for
spawning and colonisation. Populations may become established in a suitable habitat –
deep, glaciated lakes.
new lake trout populations fail to become established in small, shallow lakes with high
total dissolved solids, large littoral areas, small hypolimnions and rich fish communities,
thus restricting the likelihood of dispersal in lowland areas.
high quality spawning habitat is essential for natural reproduction of lake trout.
References
Billard R. (1997) Les poissons d'eau douce des rivières de France. Identification, inventaire et répartition des 83
espèces. Lausanne, Delachaux & Niestlé, 192 pp.
Boulva J. & Simard A. (1968) Présence du Salvelinus namaycush (Pisces: Salmonidae) dans les eaux marines
de lÁrctique occidental canadien. Journal of the Fisheries Research Board of Canada 25, 1501–1504.
Burdick G.E., Harris E.J. Dean H.J. Walker T.M. Skea J. & Colby D. (1964) The accumulation of DDT in lake trout
and the effect on reproduction. Transactions of the American Fisheries Society 93, 127–136.
Burnham-Curtis M.K. & Smith G.R. (1994) Osteological evidence of genetic divergence of lake trout (Salvelinus
namaycush) in Lake Superior. Copeia 4, 845–850.
Burnham-Curtis M.K. & Smith G.R. (1994) Osteological evidence of genetic divergence of lake trout (Salvelinus
namaycush) in Lake Superior. Copeia 1994, 843-850.
Crossman E.J. (1995) Introduction of the lake trout (Salvelinus namaycush) in areas outside its native distribution:
a review. Journal of the Great Lakes Research 21 (Suppl. 1), 17–29.
Daly R.I. Hacker V.A. & Wiegert (1962) The lake trout, its life history, ecology, and management on Lake
Michigan. Wis. Conserv. Dep. Publ. No. 233. 15 pp.
Donald D.B. & Alger D.J. (1993) Geographic distribution, species displacement, and niche overlap for lake trout
and bull trout in mountain lakes. Canadian Journal of Zoology 71, 238-247.
Furniss, R.A., 1974. Inventory and cataloging of Arctic area waters. Alaska Dept. Fish Game Fed. Aid Fish.
Restor., Ann. Performance Rept., Project F-9-6, Job G-I-I. 15: 1-45.
Goenczi A.P. & Nilson N.A. (1983) Results of the introduction of lake trout (lake charr, Salvelinus namaycush) into
th
Swedish lakes. In: Stocking of fish and crustaceans, 12 Symposium of EIFAC, Budapest 31 May – 5
June, 1982.
Healey M.C. (1978) The dynamics of exploited lake trout populations and implications for management. Journal of
Wildlife Management 42, 307–328.
Kennedy W.A. (1954) Growth, maturity and mortality in the relatively unexploited lake trout, Cristivomer
namaycush, of Great Slave Lake. Journal of the Fisheries Research Board of Canada 11, 827–852.
Lee D.S., Gilbert C.R., Hocutt C.H., Jenkins R.E., McAllister D.E. and Stauffer J.R., Jr. (1980) Atlas of North
American Freshwater Fishes. North Carolina State Museum of Natural History. 867 pp.
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Loftus K.H. (1958) Studies on river-spawning populations of lake trout in eastern Lake Superior. Transactions of
the American Fisheries Society 87, 259–277.
Marshall K.E. & Layton M. (1985) A bibliography of the lake trout, Salvelinus namaycush (Walbaum), 1977
through 1984. Canadian Fisheries and Marine Series Technical Report No. 1346. 15 pp.
Marshall K.E. (1978) A bibliography of the lake trout Salvelinus namaycush (Walbaum), 1970-1977. Canadian
Fisheries and Marine Series Technical Report No. 799. 11 pp.
Martin N.V. & Olver C.H. (1980) The lake charr, Salvelinus namaycush. – Teoksessa: Balon, E.K. (ed.), Charrs:
salmonid fishes of the genus Salvelinus: 205–277. The Hague.
Martin N.V. (1966) The significance of food habits in the biology, exploitation and management of Algonquin Park,
Ontario, lake trout. Transactions of the American Fisheries Society 95, 415–422.
McCauley R.W. & Tait J.S. (1970) Preferred temperature of yearling lake trout, Salvelinus namaycush. Journal of
the Fisheries Research Board of Canada 27, 1729–1733.
McPhail,J. & Lindsey C. (1970) Freshwater fishes of Northwestern Canada and Alaska. Lake trout. Fisheries
Research Board of Canada, Bulletin 173, 137–141.
Miller R.B. & Kennedy W.A. (1948) Observations on the lake trout of Great Bear Lake. Journal of the Fisheries
Research Board of Canada 7, 176–189.
Morrow J.E. (1980) The freshwater fishes of Alaska. University of. B.C. Animal Resources Ecology Library. 248p.
Nilsson N-A. & Dahlström H. (1968) Harmaanieriä. – Teoksessa: Svärdson, G., Nilsson, N-A., Dahlström, H. &
Tuunainen, P. – Kalat, kalavesien hoito ja kalanviljely. Kirjayhtymä, Helsinki. pp. 182–202. In Finnish.
Ryan P. &. Marshall T. (1994) Niche definition for lake trout and its use to identify populations at risk. Canadian
Journal of Fishery and Aquatic Science 51, 2513-2519.
Schmalz P.J., Hansen M.J., Holey M.E., McKee P.C. & Toneys M.L. (2002) Lake trout movements in
northwestern Lake Michigan. North American Journal of Fisheries Management 22, 737-749.
Scott W.B. &Crossman E.J. (1973) Freshwater fishes of Canada. Fisheries Research Board of Canada, Bulletin
184, 966 pp.
Spillman C.-J. (1961) Faune de France: Poissons d'eau douce. Fédération Française des Sociétés
Naturelles,Tome 65. Paris. 303 pp.
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ALIEN SPECIES SHEET
Species name: Pikeperch
(Zander)
Figure 1: Pikeperch
Image courtesy of the
Environment Agency:
Scientific name: Sander lucioperca (Linneaus)
Family Name: Percidae
The pikeperch (aka ‘zander’) belongs to the perch family (Percidae), a group of freshwater
fishes widely distributed across the northern hemisphere.
Diagnostic features
The pikeperch resembles an elongated perch but is almost pike-like in its slimness, hence its
alternative name of pikeperch (and specific name lucioperca). The pikeperch has a slender
body, with a long head and large eyes. The back and flanks are greenish-brown or greyish
with a gold sheen and dark brown, broken vertical bars. The belly is silvery white. Pikeperch
attain a maximum length of 100-130 cm, which corresponds to a weight of about 15-20 kg.
The jaws contain several large canine teeth, as well as numerous smaller teeth. The species
has two dorsal fins, with the posterior being larger than the anterior. The total number of
dorsal spines is 13-20, with 18-24 soft dorsal rays. The anal fin has 2-3 spines and 10-14 soft
rays. Both of the dorsal fins have horizontal rows of irregular black spots; the caudal fin is
also spotted.
Sander lucioperca is native to Eastern Europe and Western Asia. It occurs naturally in the
lakes and rivers from the Elbe and Vistula in te west of its distribution range, north from the
Danube to the Aral Sea, with the northernmost observations of native populations recorded
in Finland up to 64°N. The species naturally inhabits the Onega and Ladoga Lakes, as well
as the brackish bays and lagoons of the Baltic Sea. Southern populations are known from
regions near the Caucasus, inhabiting the brackish and saline water of the Caspian, Azov
and Black Seas (Bukelskis et al., 1998). The species has been introduced into southern
Scandinavia and most other parts of Northern and Western Europe.
Habitat and biology
The pikeperch is usually found in lakes, canals and slow-flowing lowland rivers (Deelder &
Willemsen 1964; Wheeler & Newman 1992). Its ideal habitat is eutrophic, shallow, turbid and
well-oxygenated waters with hard substrata (Hickley 1986). Pikeperch prefer open water,
away from dense vegetation, and feed mostly under low light conditions (e.g. dawn or dusk,
or during periods of increased turbidity). The species is primarily piscivorous, feeding on fish
of most species, including its own. Juveniles initially feed on benthic invertebrates and
zooplankton before switching to fish.
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Males mature at 2 to 4 years of age and females at 3 to 5 years, with a maximum life span of
between 10 and 13 years in most of its range, but can acieve 20+years in slow growing
northern populations. Prior to spawning fish may migrate from deep water to the shallows.
Migrations are generally 10-30 km, but can be up to 250 km (Sonesten 1991; Lappaleinen et
al. 2005). Spawning occurs from April to June in shallow water near the edges of rivers and
lakes, when water temperatures reach 12-15oC. Eggs are laid among the roots of aquatic
plants (often emergent species, e.g. reeds) or over gravel or sand. The pale yellow eggs,
measuring 1.0-1.5 mm in diameter, are laid singly and are adhesive, sticking to stones and
plants. Pikeperch produce large numbers of eggs (160 000 to 200 000 per kg of body
weight), contributing to its success in invading open waterbodies. The eggs are guarded by
both parents until they hatch (5-10 days). For optimal egg development, water temperature
must be 12-20°C, oxygen concentration above 4.5 mg/L and salinity less than 3 ppt
(Sonesten 1991, Lappalainen et al. 2005). Populations of S. lucioperca living in coastal areas
enter adjacent fresh waters for spawning (Larsen & Berg 2006).
Fish production
Aquaculture production of pikeperch in Europe is low (200-300 t) compared with capture
fisheries production (Figure 2). The rise in the 1990s was the result of French and Bulgarian
production, which has subsequently declined. Capture fisheries production has been
relatively stable since the early 1990s at around 5000 t.
8000
Capture fisheries (t)
Aquaculture (t)
7000
Production (t)
6000
5000
4000
3000
2000
1000
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
0
Figure 2. Trends in capture fishery and aquaculture production of pikeperch in Europe.
The main countries involved in aquaculture production are France (reaching 400 t in the
1990s), the Czech Republic (47 t in 2005), Hungary (28 t in 2005), Romania (42 t in 2005)
and, in recent years, Denmark (59 t in 2005). The largest contributions to capture production
of pikeperch come from Turkey (1768 t in 2005), Ukraine (408 t in 2005) and the Russian
Federation (4073 t in 2005).
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The introduction of pikeperch has created important commercial and recreational fisheries,
especially in rural areas (Crivelli 1995; Cowx 1997; Jacobsen et al. 2004), but can have
severe impacts on local, native fish populations (Braband & Faafeng 1993; Cowx 1997;
Jepsen et al. 2000. For example, the introduction of zander to Lake Egredir resulted in five
out of nine indigenous fish species disappearing, including three species of Phoxinellus, two
of which were endemic (Crivelli 1995). Pikeperch can lead to substantial declines in prey
stocks), however in the UK the perceptions of impacts to native fish stocks were not
corroborated in the numerous scientific studies undertaken (Smith et al. 1998). On
introduction to a water body, pikeperch often go through a population explosion, before
stabilising at a lower level as a balance is established. That adult zander consume their own
young may be an important regulatory mechanism. Possible impacts on local fish
• direct predation – Pikeperch consume many species of fish. The high mortality among
young age groups of prey species as a result of pikeperch predation may cause a
collapse in stocks (Hickley 1986). Pikeperch may also predate on sea trout (Salmo trutta)
and Atlantic salmon (Salmo salar) smolts as they migrate to sea (Jepsen et al. 2000).
• competition with indigenous fish for food, cover or spawning sites. For example, Schulze
et al. (2006) found perch (Perca fluviatilis) and pike (Esox lucius) populations in a shallow,
mesotrophic lake declined following the introduction of zander because they were forced
out of their preferred habitat. This could have knock-on effects on lake functioning
because perch regulate the abundance of 0+ cyprinids that control zooplankton, which, in
turn, control algal blooms (Larsen & Berg 2006).
• the introduction of exotic parasites or diseases. For example, a new nematode,
Lucionema balatonense, has been described from the swimbladder of pikeperch from
Lake Balaton (Moravec et al. 1998).
•
•
•
•
•
highly regarded as a sporting fish and has been subject to repeated illegal transfers
between waters.
environmental conditions throughout Europe are suitable for spawning and colonisation.
Populations rapidly become established in suitable habitats, although further colonisation
of new reaches of a watercourse (if unaided by man) can be slow (Hickley 1986).
predation by adult fish on their own young may be a factor in stabilising fish communities
after pikeperch introductions and initial population explosions of the fish.
capable of utilising a range of habitat types, with a preference for eutrophic, turbid waters
of low mean depth, but which are well oxygenated.
capable of migrating considerable distances, suggesting they can move to new areas
relatively quickly, but the presence of locks and barriers may slow this process. The
species does not appear to colonise faster-flowing rivers well.
Main issues
The pikeperch can pose a high risk to some freshwater systems (Cowx 1997), but the
evidence for impacts is equivocal (Smith et al. 1998) and the species supports valuable
commercial fisheries, mainly in lakes (Lehtonen et al. 1996), although these often have to be
supported by regular stocking to sustain yield (Ruuhijarvi et al. 1996, Hanson et al. 1997).
The introduction of pikeperch should be carefully assessed and the potential negative
consequences weighted against the benefits. The threat of extinction to endemic species is
proven, but the pikeperch is now established in most EU Member States. However, in areas
where the species is not present, efforts should be made to avoid its introduction. This
should orientate around education programmes to anglers and fishery managers to highlight
the detrimental impacts on indigenous fish stocks.
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There are several options available in rivers and lakes where S. lucioperca is already present
and has adverse effects on fish populations:
•
•
•
leave the species to stabilise within the community.
total removal using poisons or dewatering.
partial cull, e.g. using selective or targeted fishing, in areas where the spread can be
contained.
References
Braband, Å. & Faafeng, B. (1993) Habitat shift in roach (Rutilus rutilus) induced by pikeperch (Stizostedion
lucioperca) introduction: predation risk versus pelagic behaviour. Oecolgia 95, 38-46.
Bukelskis E., Kesminas V., Repecka R. (1998) Fishes of Lithuania: Fresh water fish (in Lithunanian). Vilnius,
Dexma; ISBN 9986-862-01-9, pp.: 118.
Cowx I.G. (1997) L’introduction d’espèces éstrangères de poissons dans les eaux douces européennes: succès
économiques ou désastre écologique? Bulletin Francais de la Peche et de la Pisciculture 344/345, 5778.
Crivelli A.J. (1995) Are fish introductions a threat to endemic freshwater fishes in the northern Mediterranean
region. Biological Conservation 72, 311-319.
Deelder, C.L. & Willemsen, J. (1964). Synopsis of biological data on the pikeperch (Lucioperca lucioperca L.).
FAO Fisheries Synopsis, Rome 28, 52pp.
Hansson S., Arrhenius F. & Nellbring S. (1997) Benefits from fish stocking experiences from stocking young of the
year pikeperch (Stizostedion lucioperca (L.)) to a bay in the Baltic Sea. Fisheries Research 31, 163-167.
Hickley P. (1986) Invasion by pikeperch and the management of fish stocks. Phil. Trans. R. Soc. Lond. B 314,
571-582.
Jacobsen L., Berg S. & Skov A. (2004) Management of lake fish populations and lake fisheries in Denmark:
history and current status. Fisheries Management and Ecology 11, 219-224.
Jepsen N., Pedersen S. & Thorstad E. (2000) Behavioural interactions prey (trout smolts) and predators (pike and
pikeperch) in an impounded river. Regulated Rivers - Research and Management 16, 189-198.
Lappalainen, J., Malinen, T., Rahikainen, M, Vinni, M., Nyberg, K., Ruuhijärvi, J. and Salminen, M. (2005)
Temperature dependent growth and yield of pikeperch, Zander lucioperca, in Finnish lakes. Fisheries
and Management and Ecology 12, 27-35.
Larsen L.K. & Berg S. (2006) NOBANIS - Invasive Alien Species Fact Sheet - Stizostedion lucioperca. - From:
Online Database of the North European and Baltic Network on Invasive Alien Species - NOBANIS
www.nobanis.org, Date of access 25/02/2007
Lehtonen H., Hansson S. & Winkler, H. (1996) Biology and exploitation of pikeperch (Stizostedion lucioperca (L.))
in the Baltic sea area. Annuals Zoological Fennici 33, 525-535.
Moravec F., Molnar K. & Szekely C. (1998) Lucionema balatonense gen. et sp. N., a new nematode of a new
family Lucionematidae fam. n. (Dracunculoidea) from the swimbladder of the European pikeperch,
Stizostedion lucioperca (Pisces). Folia Parsitoligica 45, 57-61.
Ruuhijarvi J., Salminen M. & Nurmio T. (1996) Releases of pikeperch (Stizostedion lucioperca (L.)) fingerlings into
lakes with no established pikeperch stock. Annuales Zoological Fennici 22, 553-567.
Schulze T., Baade U., Dorner H., Eckmann R., Haertel-Borer S.S., Holker F. & Mehner T. (2006) Response of the
residential piscivorous fish community to introduction of a new predator type in a mesotrophic lake
Canadian Journal of Fisheries and Aquatic Sciences 63, 2202-2212.
Smith P.A. Leah R.T. & Eaton J.W. (1998) A review of the current knowledge on the introduction, ecology and
management of zander (Stizostedion lucioperca) in the UK. In: I. G. Cowx (ed.) Stocking and
Introduction of Fish. Fishing News Books, Blackwell Science Limited, Oxford, pp. 209–224.
Sonesten L. (1991) Gösens biologi - en litteratursammenställning. Information från Sötvattenslaboratoriet,
Drottningholm 1991: 1: 1-89.
Wheeler A. & Newman C. (1992) The Pocket Guide to Freshwater Fishes of Britain and Europe. Dragon's World,
Limpsfield and London.
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ALIEN SPECIES SHEET
Species name: European catfish
Wels catfish
Danubian wels
Sheatfish
Scientific name: Silurus glanis Linnaeus
Family name: Siluridae
Taxonomy
The European catfish, Silurus glanis, belongs to the family Siluridae, a group of freshwater
fishes native to Europe, Asia and Africa. There are approximately a hundred species from
twelve genera in the family. Only two species occur in Europe: the European catfish and
Aristotle’s catfish (Silurus aristotelis). The European catfish is the largest catfish in the order
Siluriformes, which consists of approximately 412 genera and over 2400 species, and is
Europe’s largest exclusively freshwater fish. In their native habitat, European catfish can
attain lengths of 3 m and weight of 320 kg, with fish of 1 to 2 m (22-36 kg) relatively common.
Diagnostic features
The European catfish has an elongated, tapering and scaleless body, with a covering of
mucus. Colouration is variable, but the dorsal surface is darker than the flanks, which are
usually off white or yellow with dark marbling. The species has minute eyes and a very wide
mouth, with four or five rows of small teeth in the upper and lower jaws. There are six soft
feelers around the mouth, two on the upper and four on the lower jaw. The former are mobile
and very long, reaching to the base of the pectoral fins; the two pairs on the lower jaw are
stationary and much shorter. There is one small dorsal fin (1 spine and 4-5 soft rays), but the
anal fin is very long (1 spine and 90-95 soft rays), extending from the vent almost to the tail.
Most wels catfish reach only about 1.5 m long, weighing 15-20 kg , but uder good
growing conditions (mild climate, where there is a lack of competition, and good food supply),
such as in Poland France, Spain (the River Ebro) and Italy (the River Po) fish up to 150 kg
have been caught. The record was 3 m long fish, caught in the Danube in Romania weighing
about 220 kg.
Originally, the European catfish was found in the large rivers and lakes of Eastern and
Central Europe, in the Black and Caspian Seas, and in the brackish lagoons of the southern
Baltic. It was not present in the Rhine system or further west, but it has now been widely
introduced in Western Europe, including France, Germany, Italy, Spain, the Netherlands and
the UK. The species has also been introduced in Turkey, Morocco, Algeria and Syria.
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Habitat and biology
The European catfish occurs mainly in large lakes and rivers, but occasionally enters
brackish water in the Baltic and Black Seas. Outside the breeding season, the species tends
to be solitary and mostly nocturnal. The European catfish has highly advanced sensory
mechanisms (e.g. sound, smell and vibration) for finding prey, and is often described as a
voracious predator. Generally, the diets of adults are dominated by fishes, but can include
ducks, voles and crayfish, while juveniles feed on invertebrates and small fishes.
Spawning occurs between May and July, when water temperatures reach 19°C. The
female deposits her eggs (up to 30 000 per kg of body weight) in a depression in the
substrate created by the male. The eggs hatch after 3-10 days, depending upon water
temperature. The eggs and young are guarded by the parents until absorption of the yolk sac
and dispersal from the nest. The young grow rapidly, reaching up to 30 cm in length within
their first year. A seven year old fish may weigh between 1.5-7 kg (3-15 lb). Males become
mature at 2 to 3 years of age and the females at 3 or 4. The life span is up to at least 15
years, but may be up to 20-30 years.
Fish production
Aquaculture production of European catfish began in 1984, when 10 t and 4 t, respectively,
were produced in Hungary and Romania. Production steadily increased to the mid-1990s,
reaching a peak of 2010 t in 1999, before stabilising at 700-800 t (Fig. 2). The main producer
is France (mean >300 t y-1, 1995-2005), with Germany and Hungary also increasing their
production in recent years (140-150 t y-1). Capture fishery production has declined from
almost 20 000 t in the late 1980s to 8000-9000 t in the last decade (Fig. 2). The capture
fishery sector is dominated by the Russian Federation (5381 t in 2005), with Kazakhstan
(900 t in 2005) and Turkey (804 t in 2005) also contributing substantial amounts.
2500
Aquaculture (t)
30000
Aquaculture
25000
Capture
2000
20000
1500
15000
1000
10000
500
5000
2005
2003
2001
1999
1997
1995
1993
1991
1989
1987
0
1985
0
Capture (t)
3000
Year
Figure 2. Trends in the capture fishery and aquaculture production of European catfish. Note the
different y-axis for capture fishery production.
There is relatively little information on which to make an assessment of the likely impacts of
European catfish under UK conditions. Possible impacts on local fish populations and the
aquatic environment include:
Deliverable 2.5
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•
•
•
•
direct predation on other fish may cause impacts on native species.
The species is a veracious predator of fish, that can take amphibians and crustaceans,
so may have adverse effects on the environment (e.g. effects on community structure).
The European catfish can also host non-native parasites, and has been known to carry
the viral disease SVC.
•
•
•
the European catfish is highly esteemed as a sporting fish by some anglers and there is
considerable interest in increasing its distribution and availability in Europe.
capable of spawning in most European waters, but success of spawning is probably
constrained by occurrence of suitable water temperatures in northern countries.
farmed in parts of Europe for food; has been imported regularly into many countries and
is readily available through dealers and garden centres.
References
Bogutskaya N.G. & Naseka A.M. (2002) An overview of nonindigenous fishes in inland waters of
Russia. Proc. Zool. Inst. Russ. Acad. Sci. 296, 21-30.
Elvira B., (1998) Impact of introduced fish on the native freshwater fish fauna of Spain. In: I.G. Cowx
(ed.) Stocking and introduction of fish. Oxford: Fishing News Books, UK, pp.186-190..
Fijan N. (1999) Spring viraemia of carp and other viral diseases and agents of warm-water fish. In:
P.T.K. Woo & D.W. Bruno (eds) Fish Diseases and Disorders, Vol. 3: Viral, Bacterial and
Fungal Infections. CAB Int'l, pp.177-244.
Groot S.J. de (1985) Introductions of non-indigenous fish species for release and culture in the
Netherlands. Aquaculture 46, 237-257.
Keith P. & Allardi J. (coord.), 2001 Atlas des poissons d'eau douce de France. Muséum national
d’Histoire naturelle, Paris. Patrimoines naturels, 47, 1-387.
Kottelat M. (1997) European freshwater fishes. Biologia 52 (Suppl. 5), 1-271.
Lelek A., 1987 Threatened fishes of Europe. The freshwater fishes of Europe Vol.9. Aula-Verlag
Wiesbaden, pp. 343.
Maitland P.S. & Campbell R.N. (1992) Freshwater fishes of the British Isles. Harper Collins Publishers,
London, 368 pp.
Sokolov L.I. & Berdicheskii L.S. (1989) Acipenseridae. p. 150-153. In J. Holcík (ed.) The freshwater
fishes of Europe. Vol. 1, Part II. General introduction to fishes Acipenseriformes. AULA-Verlag
Wiesbaden. 469 pp.
Welcomme R.L. (1988) International introductions of inland aquatic species. FAO Fisheries Technical
Paper 294, 318 pp.
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Species common name(s): Silver Carp
Scientific name: Hypophthalmichthys molitrix (Valenciennes,
1844)
Family Name: Cyprinidae
Figure 1 Silver carp
Image taken from: http://img250.imageshack.us/img250/1318/carpidimage58dw.jpg
Diagnostic Features
Silver carp are highly similar to bighead carp and can be distinguished by a number of
characteristics. Silver carp have gill rakers that are fused to form sponge like apparatus,
whereas the gill rakers of bighead carp are not fused. Barbels are absent. The keel of silver
carp extends from the vent anteriorly to the anterior portion of the breast whereas the keel of
bighead carp extends from the vent anteriorly to the base of the pelvic fins. Adult colouration
is typically grey-black dorsally and the upper sides are olivaceous grading to silver ventrally
and laterally (Kolar et al. 2005). The maximum total length recorded for silver carp is 105 cm
and the maximum weight published is 50kg. Diagnostic: D I-III/6-7, A I-III/10-14, Pv I/7.
Scales along the lateral line: 110-124.
Habitat and Biology
Silver carp require standing or slow-flowing conditions, such as in impoundments or the
backwaters of large rivers. In its natural range, it migrates upstream to breed; egg and larva
float downstream to floodplain areas. Although benthopelagic, they are often found
swimming just beneath the water surface. It is an active species and well known for its ability
to leap out of the water when disturbed. Silver carp can be found between 6-28oC (FishBase,
2008).
Geographic Distribution
The native range of Silver carp is limited to China, Eastern Siberia (FishBase, 2008) and
Northern Vietnam (Kolar et al. 2005).
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Figure 2. Distribution of silver carp Hypophthalmichthys molitrix worldwide. Native range is kaki and
the introduced one orange (source fishbase).
The silver carp has been widely introduced across Mainland Europe, Scandinavia and the
UK, mainly for aquaculture and control of phytoplankton (Fig.3). It has only been introduced
in Greece and Italy for the purpose of fisheries. It has remained non-established across the
majority of its European range yet is thought to have entered into the Czech Republic and
Slovakia via diffusion from neighbouring countries. The first recorded introduction into
Europe occurred in France in 1950. Introductions were made into Romania, Germany,
Hungary, Poland and the Netherlands during the 1960’s, originating from China and the
USSR. Their introduction into Greece in 1980 is the latest recorded for Europe. According to
historical records, the spread from China into the rest of South East Asia started from pre
18th Century. The most intensive period of introduction in this region occurred in the period
1913-1969, the main reason being aquaculture. Date and origin of introduction into the USA
are unknown, but they were introduced for the purpose of fisheries and have become
established as a result. Introductions to South and Central American regions are recorded
between 1965 for Mexico, to 1988 for Colombia. These introductions have required
continued stocking as silver carp have not become established, with possibly the exception
of Puerto Rico. Silver carp were introduced into Fiji and New Zealand in 1968 for
phytoplankton control and research purposes. Introductions have been common place in a
number of countries from Sub Saharan Africa to South Africa, again, largely for aquaculture,
but also phytoplankton control and research purposes.
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20
18
Number of introductions .
16
14
12
10
8
6
4
2
0
Africa (12)
Asia (27)
Europe (23)
Former
North
Oceania (4)
South
USSR (10) America (9)
America (6)
Figure. 3 Histogram of the number of silver carp Hypophthalmichthys molitrix introductions per sector
(aquaculture black, angling/sport horizontal lines, fisheries vertical lines, biological control grey, other
white) for each FAO region. The category “other” includes ornamental, research, accidental and
unknown. The total number introductions in each FAO region is given in brackets as well as the total
number of populations established in the wild (white circles).
Economic uses and fish production
Silver carp is used fresh for human consumption and has also been introduced to many
countries where its ability to clean reservoirs and other waters of clogging algae is
appreciated even more than its food value. Other uses include Fisheries, research and
phytoplankton, weed and other pest control (FishBase, 2008). Figure 3 demonstrates the
extent of these reasons for introductions for each FAO region.
Worldwide silver carp production has risen from approximately $1.6 billion in 1990 to
$3.5 billion in 2005 (Fig. 4) and is currently the second largest contributor to world
aquaculture at 4 million tonnes in 2005 (FAO, 2007). The European production was at its
maximum at the end of the eighties and start of the nineties (Fig.5). In 2004, the main EU
producers were Ukraine (7,000 t), Moldova Republic (2,780 t), Romania (1,588 t) and
Hungary (1,400 t). The highest market demand for silver carp is for live fish. There are also a
number of difficulties associated with transporting live fish. “The jumping behaviour of silver
carp makes it difficult and dangerous to effectively seine fish out of aquaculture ponds (Tal
and Ziv 1978b) and can result in substantial injuries, thereby reducing the economic return of
harvested fish. In addition to the behaviour of silver carp, other factors such as short shelf life
of the flesh (Tal and Ziv 1978b; Shetty et al. 1989; Tripathi 1989), poor taste, and abundant
small bones (Tal and Ziv 1978b) reduce the appeal of the species for some consumers” (in
Kolar et al., 2005)
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Figure 4. Line graph of annual Silver carp aquaculture and capture fisheries production 1960-2004
(Raw data from http://www.fao.org/fishery/statistics/global-production).
Production in tonnes (t) .
90000
80000
70000
60000
50000
40000
30000
20000
10000
0
1950
1960
1970
1980
1990
2000
2010
Time
Figure 5 shows the European production
http://www.fao.org/fishery/statistics/global-production).
Deliverable 2.5
of
silver
carp
over
time.
(source
146
Silver carp are the fourth most often introduced fish species in the world (FAO, 2007).
Information on ecological effects has been reported for only 20 per cent (n = 18) of silver
carp introductions. Among these, three reports referred to beneficial ecological effects
following introduction and six showed some level of ecological impact. Impact appears to be
independent of whether a population has become established or not at any given location.
Both beneficial effects and adverse impacts have occurred following introduction for the
purpose of phytoplankton control and aquaculture. All associated socio-economic impacts
have been recorded as beneficial (FishBase, 2008).
The effectiveness of using silver carp as a biological control agent, mainly for phytoplankton,
remains controversial. There is evidence to suggest carp effectively reduce cyanobacteria,
however, this process is not fully understood and results have been varied (Kolar et al.
2005). Silver carp in Lake Orakai, North Island, New Zealand were capable of controlling the
phytoplankton blooms following nutrient build ups caused by rapid mixing of lake waters by
winds. Their presence improved the appearance of the lake most of the time, but did not
improve conditions for trout appreciably (McDowall, 1984). Here, and in many other cases,
habitat alteration appears to be positive. However, Hypophthalmichthys have had varying
impacts on nutrient concentrations (Opuszynski, 1980; Matyas et al. 2003 and Starling, 1993
in Kolar et al. 2005). There is insufficient evidence to support degradation of habitat by silver
carp. Competition for food resources between Hypophthalmichthys and other planktivorous
fishes has also been documented in polyculture conditions (e.g., with Catla and Rohu;
Alikunhi and Sukumaran 1964; Dey et al. 1979, in Tripathi 1989; with Common Carp;
Opuszynski 1981 in Kolar et al. 2005). The majority of studies have not quantified diet
overlap or competition for native food resources. A large body of circumstantial evidence is
building, particularly with regards to competition with native fishes that rely on plankton as a
food source (Kolar et al. 2005). In Iran, silver carp are believed to have led to the decline of
the native commercial cyprinid, Barbus sharpeyi in the Shadegan Marshes following release
from the Caspian hatcheries (Coad, 1996) however very little evidence supports these
claims. In India, It has become established in the Gobindsagar reservoir in Himachal
Pradesh, where it is known to compete with native Catla catla; it is also reported to have
affected other indigenous faunas such as Maliseer in the foot hills (Shetty et al. 1989). Kolar
et al. (2005) conclude that based on the probability and consequences of establishment,
silver carp pose a potentially high or an unacceptable risk within the US.
Control options
Several control options have been considered or explored in the US. In 2002, a $7 million
electric barrier was constructed to prevent Silver carp passing from the Illinois River to Lake
Michigan (Kuriloff, 2003). The most thoroughly researched population control for silver carp
in the US is the use of pesticides. However, this presents the problem of selectivity and
remains environmentally unsound. The use of pheromones as “bait” in fisheries is currently
under investigation (E. Little, U.S. Geological Survey, Columbia, Missouri, personal
communication, 2004 in Kolar et al., 2005)
References
Coad, B. W., 1996. Exotic fish species in the Tigris-Euphrates basin. Zoology in the Middle East
13:71-83.
FAO
(2007)
The
State
of
World
Fisheries
and
Aquaculture
2006
st
(ftp://ftp.fao.org/docrep/fao/009/a0699e/a0699e.pdf) Accessed 21 January 2008.
st
FishBase (2008) (http://www.fishbase.org/search.php) Accessed 21 January 2008. Kolar, C., D.
Chapman, et al. (2005). Asian Carps of the Genus Hypophthalmichthys (Pisces, Cyprinidae) -
Deliverable 2.5
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A Biological Synopsis and Environmental Risk Assessment, U.S. Fish and Wildlife Service: 1183.
FAO, 1997. FAO Database on Introduced Aquatic Species. FAO Database on Introduced Aquatic
Species, FAO, Rome.
Kuriloff, A., 2003. Wildlife agents launch a search for silver carp. The Time - Picayune. 22 July 2003.
McDowall, R.M., 1984. Exotic fishes: The New Zealand experience. p. 200-214. In W.R. Courtenay,
Jr. and J.R. Stauffer (eds.) Distribution, biology and management of exotic fishes. Johns
Hopkins University Press, Baltimore, USA.
Shetty, H.P.C., M.C. Nandeesha and A.G. Jhingran, 1989. Impact of exotic aquatic species in Indian
waters. p. 45-55. In: S.S. De Silva (ed.) Exotic aquatic organisms in Asia. Proceedings of the
Workshop on Introduction of Exotic Aquatic Organisms in Asia. Asian Fish. Soc. Spec. Publ.
3, 154 p.
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Environmental impacts of alien species in

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