FM-489 JUNE

PRESENT STATUS OF SHRIMP POST LARVAE
COLLECTION FROM THE PASUR RIVER AND ITS
IMPACT ON THE ENVIRONMENT
MS Thesis
M. M. PARVEJ
Department of Fisheries Management
Bangladesh Agricultural University
Mymensingh
JUNE (2014)
PRESENT STATUS OF SHRIMP POST LARVAE
COLLECTION FROM THE PASUR RIVER AND ITS
IMPACT ON THE ENVIRONMENT
A Thesis
Submitted to
Bangladesh Agricultural University, Mymensingh
In Partial Fulfilment of the Requirements for the Degree of
Master of Science
in
Fisheries Management
By
M. M. PARVEJ
Roll No.: 12 FM-JD 08M
Registration No.: 39709 Session: 2012-13
Department of Fisheries Management
Bangladesh Agricultural University
Mymensingh
JUNE (2014)
PRESENT STATUS OF SHRIMP POST LARVAE
COLLECTION FROM THE PASUR RIVER AND ITS
IMPACT ON THE ENVIRONMENT
A Thesis
Submitted to
Bangladesh Agricultural University, Mymensingh
In Partial Fulfilment of the Requirements for the Degree of
Master of Science
in
Fisheries Management
By
M. M. PARVEJ
Approved as to style and contents by
........……………………………......
...………………………...
Prof. Dr. Md. Mahfuzul Haque
Prof. Dr. Saleha Khan
Supervisor
Co-Supervisor
...................................................
Prof. Dr. Harunur Rashid
Chairman, Defence Committee
and
Head, Department of Fisheries Management
JUNE (2014)
LIST OF CONTENTS
CHAPTER
TITLE
PAGE
NO.
ABSTRACT
v
ACKNOWLEDGEMENTS
vi
CONTENTS
vii
LIST OF TABLES
x
LIST OF FIGURES
xi
LIST OF PLATES
xii
CHAPTER 1
INTRODUCTION
1
CHAPTER 2
REVIEW OF LITERATURE
6
CHAPTER 3
MATERIALS AND METHODS
15
3.1
Study area
16
3.2
Study period
16
3.3
Target group
16
3.4
Sample size and sampling procedure
17
3.5
Preparation of the questionnaire
17
3.6
Data collection methods
17
3.6.1
Questionnaire interviews
17
3.6.2
Participatory rural appraisal (PRA)
18
3.6.3
Cross-check interviews with key informants
19
3.6.4
Data from secondary sources
19
3.7
Editing and tabulating of the data
19
3.8
Processing and analysis of information
20
CHAPTER 4
RESULTS
21
4.1
21
Fishing gears used for shrimp post larvae
collection in the Pasur river
4.2
Collection of shrimp post larvae (PL)
24
4.2.1
Variation of PL caught by set bag net fisher
24
and pull net fisher
vii
LIST OF CONTENTS (Contd.)
4.2.2
Catch of shrimp PL and income of a fisher
25
family (3-4 members)
4.2.3
Timing of shrimp post larvae collection
27
4.3
Impact on the environment
27
4.3.1
Decreasing trends of shrimp PL availability
27
in the Pasur river
4.3.2
By-catch species caught during shrimp PL
27
collection in the Pasur river
4.3.3
Amount of by-catch for each shrimp post
29
larva collection in the Pasur river
4.3.4
Decreasing
trends
of
by-catch
species
29
during shrimp PL collection
4.4
Socioeconomic status of PL fishers
30
4.4.1
Training on wild shrimp PL collection
30
4.4.2
Residential
migration
of
shrimp
PL
30
collectors
4.4.3
Experience of PL fishers in the Pasur river
30
4.4.4
Time spent by the PL fishers
31
4.4.5
Investment during PL collection period per
31
year
CHAPTER 5
4.4.6
Types of PL fishers
32
4.4.7
Age structure of PL fishers
33
4.4.8
Income of PL fishers other than fishing
34
DISCUSSION
35
5.1
35
Fishing gears used for shrimp post larvae
collection in the Pasur river
5.2
Shrimp post larvae (PL) harvesting
36
5.3
Impact on the environment
36
5.4
Socioeconomic status of PL fishers
38
viii
LIST OF CONTENTS (Contd.)
5.4.1
Children and women involvement in post
38
larvae collection
CHAPTER 6
CONCLUSIONS
41
REFERENCES
43-51
ix
LIST OF TABLES
TABLE
TITLE
NO.
1
PAGE
NO.
Comparison of shrimp post larvae collection by pull net
23
and set bag net in the Pasur river during the study
period.
2
Variation of PL caught by set bag net fisher and pull net
25
fisher in the Pasur river.
3
Catch of shrimp PL and income of a fisher family (3-4
26
members).
4
By-catch species caught for a single shrimp PL during PL
28
collection in the Pasur river.
5
Total amount of by-catch for each shrimp post larva
collection in the Pasur river.
x
29
LIST OF FIGURES
FIGURE
TITLE
NO.
PAGE
NO.
1
Design of the research methodology.
15
2
Map of southwest Bangladesh showing the study area of
16
the Pasur river.
3
Net used by the PL fishers of the Pasur river during
24
March-November, 2013.
4
Experience of PL fishers in the Pasur river.
31
5
Time spent by the fishers in the Pasur river.
31
6
Investment by PL fishers during collection period per
32
year in the Pasur river.
7
Types of PL fishers of the Pasur river.
33
8
Age structure of PL fishers of the Pasur river.
33
9
Income of PL fishers other than fishing.
34
xi
LIST OF PLATES
TABLE
TITLE
NO.
1
PAGE
NO.
Data collection from PL collectors through questionnaire
18
interview.
2
Focus group discussion with PL collectors and fry
19
traders.
3
PL collectors using stationary gear (set bag net) in the
21
Pasur river.
4
PL collectors using mobile gear (pull net) in the Pasur
22
river.
5
Children in PL collection in the Pasur river during the
39
survey period.
6
Women in PL collection in the Pasur river during the
survey period.
xii
40
PRESENT STATUS OF SHRIMP POST LARVAE
COLLECTION FROM THE PASUR RIVER AND ITS
IMPACT ON THE ENVIRONMENT
M. M. PARVEJ
ABSTRACT
The culture of prawn and shrimp started in the coastal belt during the early ‘80s to
supply international markets and generate foreign exchange. The industry is
primarily reliant on Post Larvae (PL) caught in coastal areas although some
shrimp PL hatcheries have been established but these are insufficient to meet the
increasing demand. The wild PL were collected in the coastal areas and sold
among the gher farmers. The study was conducted to know the present status and
assess the impact of PL collection on other aquatic species in the Pasur river near
Mongla in southwest Bangladesh from January to December, 2013. The post larvae
of shrimp were available for 9 months, from March to November. The peak period
was found during April to August. The highest catch (301 PL/day/fisher family)
found in the month of June and the lowest catch (142 PL/day/fisher family) in
November. The most common gear used was the set bag net (Net jal or Behundi jal)
which is approximately 2-4 m wide and 10-15 m long with a very fine mesh size.
The PL fishers earned their livelihood by selling the harvested PL. The present
study showed that the highest income (Tk. 22575) of a fisher family (3-4 members)
was in June and the lowest income (Tk. 3834) was in November. The study
revealed that, while sorting the most desired post larvae of shrimp, all other
species caught in the net was thrown on dry land, causing potential damage to the
aquatic ecosystems, biological diversity and natural recruitment of populations of
the brackish water environment. The present study indicated negative impacts of
PL collection on the recruitment of many fish and invertebrate species in the river.
Fish and crustacean availability is decreasing due to over fishing of shrimp PL.
There was a huge ‘by-catch’ associated with intensive fishing for PL in the Pasur
river. ‘By-catch’ for a single shrimp PL were about 254 post larvae of shrimp and
prawn and 217 post larvae of fish and many other aquatic animals.
v
ACKNOWLEDGEMENTS
All the gratefulness of the author goes to the Almighty Allah, who has kindly made the author
successful to pursue the higher study and to complete the research work and thesis for the degree of
Master of Science (MS) in Fisheries Management.
The author expresses heartfelt gratitude, the deepest sense of respect, immense indebtedness and the
best regards to his research supervisor, Prof. Dr. Md. Mahfuzul Haque, Department of Fisheries
Management, Bangladesh Agricultural University (BAU), Mymensingh for his scholastic
supervision, constructive criticism, intellectual guidance, valuable suggestions and affectionate
feeling in planning, conducting and completing the study.
The author also expresses his heartiest appreciation and deep sense of respect and gratitude to his
research co-supervisor, Prof. Dr. Saleha Khan, Department of Fisheries Management, BAU,
Mymensingh for her co-operation and suggestions to overcome many errors and comments in
upgrading the quality of the research work and to show the author the right path during the course
of this work.
The author is greatly indebted to his honourable teacher, Prof. Dr. Harunur Rashid, Head o f the
Department o f Fisheries Management, for his constant inspiration and kind co-operation in
performing the research activities precisely.
The author feels pleasure to extend his heartiest respect, deepest gratitude and cordial thanks to all
respected teachers of the Department of Fisheries Management, BAU, Mymensingh for their
valuable teaching, inspiration and encouragement during the whole course of study.
The author expresses his special thanks and appreciation to all the interviewed shrimp PL fishers for
their kind cooperation and support in completing the research work.
The author humbly desires to acknowledge his heartfelt appreciation and profound thanks to all his
friends and well-wishers, especially Amin, Mehedi, Imran, Hasan, Ali, Sumon, Mohaiminul, Jasim
for their help in data collection and inspiration throughout the study period.
Finally, the author acknowledges with great regards and pleasure, his deepest sense of gratitude and
thanks to his beloved parents, brothers, sisters and relatives, who sacrificed a lot during his studies
and were the constant source of inspiration.
The author
JUNE (2014)
vi
CHAPTER 1
INTRODUCTION
The culture of shrimp and prawn in the coastal zone is a major export earning
activity for Bangladesh. This culture started in the coastal belt during the early
‘80s to supply international markets and earn foreign currencies (Islam et al.,
2001). The Government and private sector intensified efforts to increase export
earnings from this sector. This industry was initially dependent on natural
sources for seed supply (Khan, 2002). Though a few shrimp post larvae (PL)
hatcheries have been established in shrimp farming region to produce seed and
meet the growing demand for PL, supply is still insufficient to meet industry
requirements. As a result people are collecting Post Larvae (PL) from natural
stock, which causes destruction of huge number of fish fry of different species.
Due to this practice the wild fish stock might be affected (Khan and Latif, 1997).
Farmers think wild post larvae to be of excellent quality. Moreover, the survival
of wild post larvae has been reported to be much higher than that of hatcheryproduced fry (Muir, 2003). At present, there are 61 shrimp (bagda) and 70
prawn (golda) hatcheries in Bangladesh, although many are non-operational
due to lack of knowledge of the complex hatchery technology, inadequate
manpower, and insufficient supply of wild brood stock. Hatchery production
can supply about 9450.3 million (shrimp 8200 million and prawn 1250.3 million)
post larvae annually; only 25-30% of total demand (DoF, 2013). Nevertheless,
the Department of Fisheries (DoF) in Bangladesh imposed a ban on wild post
larvae fishing in 2002. This ban primarily originated from concern for potential
negative effects on by-catch (i.e., non-target species) that has an impact on
environment in coastal ecosystems. However, this ban has not been strictly
enforced because of the limited availability of hatchery fry and the lack of
alternative livelihoods for poor people engaged in post larvae fishing (Ahmed
et al., 2013).
1
The total number of PL (both bagda and golda) collection from wild sources
was 900 million in 2012. In 2011-2012 fiscal year, Bangladesh exported 48007
metric ton of shrimp and prawn valued at around 36402 million taka of which
70% contributed by shrimp and 30% by prawns (DoF, 2013). Post larvae fishing
contributes substantially to the local and national economy and also is a part of
foreign exchange earnings. The shrimp is a highly valued product for
international markets, and thus, most shrimps are exported, especially to the
USA and Europe (Ahmed et al., 2013).
Bangladesh is very rich in fish, crustaceans, mollusks and other aquatic animal
biodiversity. Inland water bodies are known to be the habitat of 260 species of
indigenous fish, 12 exotic fish, 56 prawns, about 24 freshwater mollusks and 150
birds (DoF, 2013). The marine water bodies (200 nautical miles along the coast)
of the country are also remarkable for being habitat of 475 species of fish, 36
marine shrimps and about 336 mollusks (Sarker and Sarker, 1988).
The coastal zone of our country characterizes a rich and unique biodiversity. It
has a great natural ecosystem value in terms of scientific interest and because of
its outstanding aesthetic value. It also provides multiple renewable resources of
direct economic benefits to the nation. Coasts are dynamic interface zones
involving the meeting of atmosphere, land and sea. The coastal zone also
provides an important buffer zone and filtering system for the coastal
ecosystem. All these components are in a fragile balance controlled by physical
and biological processes which can be easily upset by natural or humaninduced perturbations (Viles and Spencer, 1995). The interaction between
human societies and the environment in this zone is very pronounced in the
coastal regions of Bangladesh. Hence coastal resource management has become
important and imperative for nutritional, economic and environmental reasons
(Bergin and Michaelis, 1996).
Shrimp farming is currently one of the most important sectors of the national
economy of Bangladesh. During the last two decades its development has
attracted considerable attention because of its export potential. Consequently a
2
vast area in the coastal zones of Khulna, Satkhira, Bagherhat and Cox’s Bazar
has been converted into shrimp farm. The most widely cultured fast growing
species in Bangladesh are giant tiger prawn or Asian tiger shrimp or black tiger
shrimp (Penaeus monodon) and giant freshwater prawn (Macrobrachium
rosenbergii). Shrimp farming of Bangladesh at least partially depends on wild
post larvae (Angell, 1990; Ahmed, 2000; DoF, 2002).
Traditionally, shrimp farmers have preferred to stock their gher (shrimp farms
are locally known as gher) with wild PL rather than hatchery-produced fry
because the production of hatchery PL has been limited and farmers consider
them to be of lower quality (Angell, 1992; Ahmed et al., 2005). In addition, the
survival of wild PL is reported to be much higher than that of hatcheryproduced fry. It has been estimated that approximately 2 billion shrimp fry are
collected annually from wild sources in Bangladesh. With respect to freshwater
prawn (M. rosenbergii) more than 90% of the total PL is derived from natural
sources and in the case of black tiger shrimp (P. monodon), more than 50% is
derived from wild sources (Banks, 2003).
Wild PL collection has given employment opportunity for thousands of coastal
landless and unemployed people (Angell, 1990; FAO/NACA, 1995; Islam and
Wahab, 2005). In Bangladesh more than 0.42 million people are involved in
shrimp seed collection (USAID, 2006). On the other hand, wild PL fishing has
assumed a notorious impact on coastal biodiversity (Primavera, 1998; Islam et
al., 1999; Hoq et al., 2001; Bhattacharya and Sarkar, 2003). It has been reported
that about 99 finfish and other prawn species are discarded for collecting a
single shrimp or prawn PL (Rashid, 2000), which is a great threat to the
biodiversity.
Pasur river is a big river in the Sundarban area as an extension of the Rupsa
river. South of Khulna, the Bhairab or the Rupsa flows further south and is
renamed as Pasur near Chalna and falls into the Bay of Bengal flowing to the
right of Trikona and Dubla islands. South of Mongla upazilla the river flows
into the Sundarbans. The maximum flow of the Gorai-Madhumati passes into
3
this river through the Nabaganga. The Pasur is placed after the Meghna in size
in the deltaic region. The river is joined by Mongla canal at about 32 km south
from Chalna. Flowing further south the river meets the Shibsa at about 32 km
north from its mouth and debouches into the sea keeping its original name
Pasur. The river is very deep and navigable throughout the year and large
marine ships can easily enter Mongla Sea Port through it. The Pasur is an
important river route through which Khulna-Barisal steamboats and other
vessels ply. The river is about 460 m wide at Rupsa, about 790 m at Bajuyan and
about 2.44 km at the confluence of the Pasur-Shibsa. The total length of the river
is about 142 km. The Pasur and all its distributaries are tidal channels (Ahmed
et al., 2013).
The Pasur river adjacent to the Sundarbans is also an important nursery,
feeding, and breeding grounds for many species of fish, crustaceans, crabs,
snails, oysters, mollusks, and turtles. The most common, commercially
important by-catch species discarded from the harvesting of wild shrimp PL in
the Pasur river are:
(1) shrimp-white shrimp (Penaeus indicus), shrimp (P.
merguiensis), shrimp (Metapenaeus monoceros); (2) prawn- monsoon river prawn
(Macrobrachium malcolmsonii), freshwater prawn (M. villosimanus), freshwater
prawn (M. mirabilis), freshwater prawn (M. birmanicus), freshwater prawn (M.
rude), freshwater prawn (M. dayanus) and (3) fish- Hilsa shad (Tenualosa ilisha),
Indian river shad (Gudusia chapra), sea bass (Lates calcarifer), loita (Harpadon
nehereus), tengra (Mystus spp.), punti (Puntius spp.), baila (Glossogobius spp.),
boal (Wallago attu) etc.
Thousands of rural poor are involved in shrimp post larvae (PL) collection on
the Pasur river from Mongla to Heron Point on the south coast as part of their
livelihood. Fry collectors used mainly two types of gear—pull net and set bag
net. The pull net is a rectangular one, locally called Baksho jal. The set bag net
(locally called Net jal or Behundi jal) represented 95% of the total nets. This net is
set with the help of a boat that is supported by an anchor against the current.
The net length varies from 10 to 15 meters and the width varies between 2 to 4
4
meters. It is set at the 3 to 8 meters depth (Ahmed, 2003). The collection of wild
PL also makes a significant contribution to the income of poor marginal fishers
in the Pasur river who are engaged in prawn related activities such as trade in
fishing gear, transport of the harvested PL and many others.
Shrimp post larvae collection is a regular activity in the Pasur river throughout
the year. The PL collection activities in the river started since 1980s, the
beginning period of PL collection. This river is very significant for PL fishing
because of the availability of shrimp and prawn wild post larvae. The whole
area of this river, as good as, is exploited mainly for PL fishing which provided
financial stability and livelihood for PL collector who lived near coastal area of
the Pasur river. The fisher communities are indiscriminately practicing PL
fishing which obviously threat to the Pasur river biodiversity. They sell their
harvested PL to local PL traders or market. During the peak season they earn
huge money.
This study surveyed the PL fishing and its related activities for one year which
covered one kilometer of the Pasur river adjacent to Mongla port. The main
purpose is to know the present scenario of PL fishing of the Pasur river.
Objectives:
1. To know the present status of shrimp post larvae collection from the
Pasur river ;
2. To assess its impact on the environment (fishes and other aquatic
animals).
5
CHAPTER 2
REVIEW OF LITERATURE
Available published literatures related to the present study have been reviewed.
Some of them are presented below.
Karim (1986) stated that the catching, sorting and transportation method result
in a high degree of mortality of the shrimp fry itself (10– 50%) increasing further
the demand for seeds.
Funegaard (1986) described the gears and methods used in fishing of bagda
shrimp fry in the estuarine and near shore waters and also examined the
sorting procedure of bagda fry. He also made observation on the vulnerability
of bagda fry with simultaneous destruction of zooplankton communities along
the coastal belt of Satkhira based on only 6 weeks observation which is too little
for highlighting the prevailing condition of shrimp fry fishing in Bangladesh.
Larsson (1986) estimated that 20,000-25,000 people were engaged in bagda PL
collection in Satkhira district in 1985 during the peak fry collection season. He
also mentioned the catch of 200 fry/day/gear (all types mixed) in the peak
season in Satkhira district.
Mahmood (1990) paid attention for providing a first-hand assessment on the
quantum of damage caused to zooplankton while collecting of bagda PL during
the period between June, 1982 and July, 1983 in Chakaria, Satkhira and
Khepupara. He also recorded that for fishing a single individual of Penaeus
monodon PL, 1,631 zooplankton was destroyed. It is worthwhile to mention here
that Mahmood used a rectangular net with small mesh size (0.5 mm), whereas
the seed collectors mainly used nylon net with double mesh size (1 mm). So, by
using gear with selective mesh size may help to reduce the destruction of
aquatic organisms.
Alam (1990) studied the indiscriminate exploitation and quantify the loss of
micro and macro aquatic organisms as a by-catch during the collection of P.
monodon PL in the Teknaf and Cox’s Bazar areas. He noted that for each P.
6
monodon PL, about 21 other shrimps, 30 finfishes and 46 zooplankton were
damaged. He also made observation that about 650.5 million P. monodon PL
was harvested in Cox’s Bazar and Teknaf areas during the period between 1988
and 1989.
Paul (1993) reported that fry collection increased rapidly in the greater Khulna,
Patuakahali, and Cox’s Bazar region to meet the increasing demand. He also
estimated that average catch rate of P. monodon larvae was 35 fry/day for PN
(push net) and 70 fry/day for FBN (fixed bag net). Subsequently, approximately
60,000 or more fry collectors were found to be engaged in this activity.
Khan et al. (1994) worked on the effects on shrimps stock in relation to
exploitation manner and did a short survey work on the status of shrimp fry
collectors.
They also reported that about 2,035 million PL were annually
collected by the shrimp seed collectors in the whole coastal region of
Bangladesh and which comprises only about 1% of the total larvae catch. The
rest of the catch which composed of other shrimp species, finfishes and
zooplankton were thrown on the sandy beach to die. They studied that for
indiscriminate killing of other organisms might be affected the food chain in
nature. They stated that during the period of segregation the seed collectors
discarded all other fries except bagda PL. They made observation on the effect
of estuarine set bag net on the marine fisheries of Bangladesh. They found 3
types of gear: push net, drag net and fixed bag net in particular used to collect
shrimp fry and 693,000 gear units were recorded during the study period. They
also mentioned that the activities of tiger shrimp collection damage billion of
other valuable penaeid, non-penaeid shrimps, finfishes and other zooplankton.
Hoq et al. (1995) found that the harvesting of wild PL had emerged as an
important economic activity for the coastal communities.
Anon (1995) reported that total catch of P. monodon PL was 1.06 million in
Rampal and Mongla thana of Bagerhat district and Dacope thana of Khulna
district during the period of January 1995 to June 1995. He also observed
enormous destruction of other shrimp and finfish larvae by-catch and it was
7
estimated about 216 million. He also noted that shrimp fry by-catch comprises a
wide variety of shrimp and finfish species that have some economic importance
and others are important for ecological balance of the estuary. These include:
Penaeidae (Metapenaeus brevicornis, M. ensis), Sergestidae (Acetes indicus),
Palaemonidae (Macrobrachium sp.), Clupeidae (Hilsa spp.), Mugilidae (Mugil
sp.), Engraulidae (Stolephorus sp.), Gobiidae (Glossogobius giuris, Apocryples bata),
Anguilidae (Anguilla spp.), Cynoglossidae (Cynoglossus sp.) Tetraodontidae
(Tetraodon spp.) etc.
Islam et al. (1996) reported that in Satkhira coastal region for collecting each P.
monodon PL, seed collectors killed about 38 other shrimps, 6 finfishes and 56
other macrozooplankton. They also reported that during collection of each P.
monodon post-larva, about 17 larval specimens of other shrimps, larvae of 8
finfishes and 92 other macrozooplankton were destroyed in the Meghna
estuaries of Bhola district and about 15 million of bagda PL was collected
during 1993. They observed that about 45,000-50,000 people were engaged in
fry catching during the peak period (Feb. /March) in Satkhira region and about
0.19 million men were engaged in fry catching in Bhola district.
Primavera (1997) described that the indiscriminate and extensive harvesting of
wild prawn PL has been directly linked to the destruction of important coastal
ecosystems including mangrove forests. However, the mangrove forests and
associated ecosystems have remained a source of livelihood for coastal fisher
folks, providing the population with a direct source of food items including
fish, crustaceans, and mollusks in addition to numerous other economic
activities linked to the mangrove ecosystems.
Rahman et al. (1997) reported that in polder 18/19, 22 and 20 under Paikgacha
upazilla, seed collectors killed 700 different shrimp and finfish larvae during
the collection of each P. monodon PL as a target species. They investigated that
for collection of each bagda PL, about 37 larvae of other shrimp species, 12
finfishes and 10 macrozooplankton were killed during the process of shrimp
seed collection in Barguna coastal region (Baleshwer and Bishkhali river). They
8
also recorded that about 1.3 million P. monodon PL was harvested during the
year 1993. They made observation that for each P. monodon PL collection about
27 other shrimp larvae, 22 finfishes and 23 macrozooplankton were destroyed.
From the same study it has been recorded that about 2.9 million men were
found to be engaged in fry catching and 480 million bagda PL were harvested
during 1993 in the Patuakahali coastal region (Andhermanik river and Kuakata
sea shore). They recorded that about 0.2 million bagda PL collectors were found
in the coastal region of Bangladesh.
Primavera (1998) reported an estimated loss of 475 juvenile shrimp in Malaysia,
15–330 in Philippines, and 47–999 in India for every single PL.
Karim (1999) reported the availability of tiger shrimp fry throughout the coastal
areas of Bangladesh. He also mentioned that shrimp fry were available from
September to May in the adjacent rivers of Sunderbans; December to March in
the tidal rivers of Satkhira district and from April to August in Cox’s Bazar
district.
Kamal (2000) suggested that P. monodon PL constitute at most 1% of the total
collection in Bangladesh, amounting 1–3 billion per year. He also stated that the
remaining 99% would total about 99–297 billion. One recent report shows that
more than 100,000 collectors were engaged in this activity with a total loss of
about 180,000 million of other aquatic organisms in Bangladesh.
Naylor et al. (2000) reported that the magnitude of annual fry by-catch is
estimated at 63 million to 2.6 billion in just three collection centers in West
Bengal, India.
Ahmed (2001) studied the final composition of behundi fishery in a fixed area of
the river Galghasia under Satkhira district. He reported that many marine and
certain freshwater migratory fauna appear in the area during particular season
or time to use the area as nursery ground. The fauna composed of shrimps (4
families), fish (17 families), mantis shrimp (1 family) and crab (1 family) and
most of them are young. He also conducted a taxonomic survey to make a
complete systematic record of the species so far been reported from Bangladesh
9
and recorded other unknown available species of both marine and brackish
water habitats.
Quddus et al. (2001) described 139 species of bony fishes, 15 species of penaeid
shrimps, 2 species of solenocerid shrimps, 10 species of caridean prawns, 3
species of lobsters and 15 species of crabs from fresh to brackish and marine
waters of Bangladesh.
Hoq et al. (2001) reported that 12–551 PL of other shrimps, 5–152 finfish larvae
and 26–1636 macro zooplankton are wasted during the collection of a single P.
monodon PL in major rivers of the mangrove forest in Bangladesh. They also
found that the abundance of P. monodon PL was significantly reduced from 1992
to 1999 and the shrimp fry fishery is responsible for declining other important
fishery such as the hilsa fishery and crab fishery in coastal Bangladesh.
Islam et al. (2001) estimated that about 61.7 million, 6.7 million, 14.3 million,
222.8 million, 13.8 million and 816.7 million of bagda PL were harvested in
Khulna, Satkhira, Bagerhat, Patuakhali, Noakhali and Cox’s Bazar coastal
region respectively. They also found that for collecting each bagda PL, average
of 96 other shrimps, 19 finfishes and 435 zooplankton are killed in Khulna
region; 371 other shrimps, 274 finfishes and 938 of zooplankton in Bagerhat
region; 121 other shrimps, 26 finfishes and 329 of zooplankton in Patuakhali
region; 104 other shrimps, 74 finfishes and 124 zooplankton in Noakhali region;
5 other shrimps, 12 finfishes and 27 zooplankton in Cox’s Bazar region during
the period between 1998 and 2000. They reported that about 0.51 million men in
Khulna, 0.33 million men in Satkhira, 0.27 million men in Bagerhat, 1.8 million
men in Patuakhali, 0.12 million men in Noakhali were found to be engaged in
fry catching during the period between 1998 and 2000.
Paez-Osuna (2001) found that the harvesting of wild PL for seed in the
aquaculture and prawn farming sector is an important feature of aquaculture
ventures and remains a critical point in the prawn farming activities in many
countries worldwide.
10
World Bank et al. (2002) recorded that hatchery produced PL seed is now
available in several countries in Asia and Latin America, wild PL still remains
the significant and often preferred source of seed for the extensive systems
especially among the rural poor population worldwide.
Stanley and Alduvin (2002) reported that some 3000 larva gatherers are
reported to operate in the Gulf of Fonseca, Honduras and the possible loss of
by-catch from this activity is reported as 3–34 for every larva captured.
Begum and Nazmul (2002) stated that the overall survival from the egg stage to
recruitment is highly density dependent; they suggested that if densitydependence occurs after the PL stage, then the harvesting of PL would have
little effect on recruitment and, if density-dependence occurs before the PL
stage, then PL harvesting would have a direct and proportional effect on
recruitment and fishery yield.
Sadek et al. (2002) reported that based on the comparison of growth rate and
corresponding value of the PL between those left in the wild (to be harvested by
capture fisheries) and those collected for aquaculture rearing (6 vs. 0.38 g/PL
and 0.01 vs 0.0025 US$/PL), they concluded that PL harvesting is not
intrinsically irrational or wasteful. However, this conclusion was not based on
practical time-series data on the stock size, recruitment pattern and the level at
which wild shrimp fry can be exploited without affecting the original wild
stock. The authors also ignored the ecological importance of the fishery as well
as the loss of other fishery resources associated with shrimp fry collection. Such
comment is, therefore, may be strongly criticized while shrimp fry fishery itself
is in a steadily declining trend.
Frankenberger (2002) showed that wild prawn PL harvesting remains an
important source of income and livelihoods for the coastal poor and estimates
show that over 40% of the mostly landless households living along the coast are
involved in PL collection.
Paez-Osuna et al. (2003) attributed the declining catches of wild prawns and
fishes in many coastal ecosystems to overexploitation both in terms of
11
harvesting of food fish and shellfish as well as the impacts of the fishing
practices on the aquatic ecosystems. They also noted that the expansion and
intensification of the prawn culture systems has also reduced the agricultural
land available for the farming of the rice which forms the staple food for
majority of the coastal Bangladesh population. They investigated the
livelihoods of many artisanal fisher folks in the marine, coastal and estuarine
fisheries of Bangladesh who are under serious threat due to the continued
destruction of coastal ecosystems and declining fishery yields.
Muir (2003) stated that the coastal ecosystems of Bangladesh serves as a nursery
ground for many prawn, fish and other aquatic species since they provide
physiologically suitable environment with respect to temperature, salinity and
other physico-chemical parameters. Millions of tiny larvae, post larvae and
juveniles are swept into the intertidal areas and associated ecosystems where
they complete crucial stages of their lifecycles. He also reported that majority of
farmers prefer wild PL because of their hardiness, with the survival of wild PL
reportedly higher than hatchery produced PL.
New (2005) monitored that the high demand for PL, low investment for
harvesting of wild PL and the high returns associated with these fishing
ventures encouraged thousands of coastal folks especially girls, poor families
and other vulnerable and low income groups of the society to embrace the
harvesting of wild PL as major source of livelihood. Consequently, there is a
need for socioeconomic and environmental research to understand the state of
current production and harvesting of wild PL and ensure responsible resource
use practices for minimal environmental impact.
Ahmed et al. (2005) reported that the harvesting of wild PL lasting only few
months of the year can contribute a relatively substantial part of the annual
incomes of the poor and vulnerable groups among the coastal communities as
well as to the economy of coastal zones of Bangladesh.
USAID (2006) found that together with trade in prawn PL, both ventures
account for over 60% of the total income of landless poor. The collection of wild
12
PL also makes a significant contribution to the incomes of poor marginal
farmers who are engaged in prawn related activities such as trade in fishing
gear, transport of the harvested PL and other activities. It is difficult to
determine how many people are actually involved in fry collection since some
are engaged in the activity on a full time basis and some as a part time
occupation. However, it was reported that the livelihoods of about 400,000
people including women and children are associated with prawn PL fishing in
coastal Bangladesh and more than 2000 million PL valued at around US$ 30
million are collected from these coastal zones every year.
FAO (2007) recorded that the harvesting of wild prawn PL forms a relatively
good source of income and only lifeline for some of the coastal poor, this
practice has substantial negative impacts on estuarine and marine fishery and
prawn stocks. This is because during the PL collection, many other non-target
fin and shellfish species larvae and juveniles are caught and discarded during
the selection of the target species. This is in contrast to brackish water prawn
culture which involves high value species that are often exported along with
much of their production chain.
Khondaker (2007) recorded that in Bangladesh, there is limited availability of
hatchery produced PL and the current production supplies only about 20% of
total demand, hence the harvesting of wild PL remains the only alternative to
the demand and supply gap in the rapidly expanding prawn farming ventures
in the country.
Iftekhar and Takama (2008) described that the impacts of the ecosystem
degradation, destruction of the mangroves forests and the resultant loss of
wildlife, the increase in flood risks and other natural disasters such as typhoons
and tsunamis which threaten the lives and properties of the wider coastal
populations cannot be over emphasized.
Ahmed et al. (2010) reported that the harvesting of wild PL in the coastal areas
of Bangladesh runs all year around with a peak season during April to June
during spring tides (when the high tides are very high and the low tides are
13
very low) when the numbers of planktonic PL are reportedly high. They also
reported that the crude and indiscriminate harvesting of wild PL involves
removing a large proportion of several species of shellfish, finfish and other
pelagic biota as by-catch. Due to high market demand for the wild PL and low
or zero value of much of the by-catch, the fishers only retain the targeted PL
which obtains the maximum price in the trade. Therefore, after sorting out the
target PL species, the entire by-catch is discarded on the river banks and shores
of the harvested water bodies.
Ahmed et al. (2012) stated that the fishing gears employed in the harvesting of
PL include push/pull nets, drag nets used behind boats and passive set bag
nets. The push/pull nets are primarily used by women and children and are
used along the estuarine riverbanks and intertidal areas and the push/pull net
fishers represent the poorest groups since the gear requires very little capital to
invest and are the cheapest options for the coastal poor. They also reported that
set bag nets are used in the middle of the river as well as also along the coast
and are considered to be the most efficient gears accounting for a greater bulk
of the catch of wild PL as well as by-catch. These types of gears also require
boats, a strong anchor line as well as buoys such as drum or barrels and
therefore calls for a considerable amount of capital. Consequently, set bag net
fishers are considered to belong to the better-off households that have access
higher capital. They stated that the indiscriminate harvesting of PL present a
threat to the fisheries resources on which the coastal fisher folks are dependent
on as well as to the wider ecological biodiversity on which the fisheries are
based.
14
CHAPTER 3
MATERIALS AND METHODS
The present study was conducted following some steps which are presented in
Figure 1.
Selection of the title and objectives of the study
Selection of the study site
Selection of target group
Timing of data collection
Collection of set bag net (Net jal or Behundi jal) and pull net catches
Sorting of PL from other organisms
Counting of PL, juvenile fishes and other shrimps
Data recording
Data analysis
Preparation of tables and figures
Explanation of the results and thesis writing
Figure 1: Design of the research methodology.
15
3.1 Study area
The study was conducted in the Pasur river adjacent to Mongla upazilla under
Bagerhat district, a coastal area of the Bay of Bengal, situated in the southwest
part of Bangladesh (Figure 2). This region is important for shrimp and prawn
post larvae (PL) collection and marketing. The total length of the Pasur river is
about 142 km.
Figure 2: Map of southwest Bangladesh showing the study area of the Pasur
river.
3.2 Study period
The field research was carried out for a period of twelve months from January
to December 2013. Shrimp PL collectors collected PL for 9 months (March to
November). During winter shrimp PL were less available and for that reason
the fishers did not collect PL.
3.3 Target group
Shrimp post larvae (PL) collectors were considered as the target group of the
study in the Pasur river.
16
3.4 Sample size and sampling procedure
In the study area 300 fisher families were present among them 100 fishers were
selected proportionately from 1 kilometer of the Pasur river by using random
sampling. To achieve the objectives of the study a comprehensive interview
schedule of structured questionnaire was used to collect data.
3.5 Preparation of the questionnaire
In order to get a complete picture of the present status of Shrimp PL collection
and to fulfil the objectives of the study, a questionnaire was prepared and pretested. In this pre-testing, attention was paid to incorporate any new
information that was not designated to ask in the draft schedule. Thus,
questionnaire was changed, modified and rearranged according to the
experience gathered in the testing for ensuring the consistency and applicability
in actual field condition. The final schedule was then developed in logical
sequences,
so
that
the
PL
collectors
could
answer
chronologically.
Questionnaire was constructed in English and translated in Bengali (Bangla)
during face-to-face interview.
3.6 Data collection methods
In order to collect relevant information, interview technique was followed. For
the study a combination of questionnaire interviews, participatory rural
appraisal (PRA) tools such as focus group discussion (FGD) and key informants
interviews were used for data collection.
3.6.1 Questionnaire interviews
The PL fishers were interviewed at the fishing sites or river banks. Time
required for each individual interview was about 1 hour. The interviews
focused on shrimp post larvae fishing, duration of fishing time, by-catch rate,
daily income, constraints of fishing, major risks, environmental impacts, and
socioeconomic status etc.
17
A
B
Plate 1 (A-B): Data collection from PL collectors through questionnaire
interview.
3.6.2 Participatory rural appraisal (PRA)
For the present study, the participatory rural appraisal (PRA) tool focus group
discussion (FGD) was conducted with members of coastal fishing communities,
including larvae collectors, fry traders, women, and children. A total of 5 FGD
sessions were conducted with a group size of 4-6 persons; the duration of each
session was approximately 1.30 h. FGD sessions were held on the river bank, at
fisher houses, and at larvae market. FGD was used to get an overview of
qualitative information on larvae fishing and marketing systems, environmental
impacts of larvae fishing, overall constraints of fishers, and their socioeconomic
conditions.
18
A
B
Plate 2 (A-B): Focus group discussion with PL collectors and fry traders.
3.6.3 Cross-check interviews with key informants
Key informants are purposely selected community members who were able to
provide information on a particular topic based on their knowledge, skills or
experience. Selected key informants such as village old man, fry trader, NGO
representative and fisheries officer were interviewed by a semi-structured
questionnaire. Semi-structured interview usually involves a set of guide
questions or discussion points. Key issues came from focus group discussion
was also discussed with the key informants to have more logical explanation.
3.6.4 Data from secondary sources
Secondary data were collected from articles, project reports, journals and maps,
internet and other theses; government institution and research organization like
Department of Fisheries (DoF) and Bangladesh Fisheries Research Institute
(BFRI).
3.7 Editing and tabulation of the data
The collected data were edited, summarized and processed for analysis. These
data were verified to eliminate all possible errors and inconsistencies. Simple
statistical tools like averages and percentages were used for the analysis of data.
19
Finally, the processed data were transferred to MS Excel sheet from which
classified tables were prepared revealing the finding of the study.
3.8 Processing and analysis of information
Mainly tabular analysis was used in this study. Data were presented mostly in
the tabular form, because of the simple collection techniques, widely used and
easy to understand. For processing and analysis purpose, MS Excel and MS
word have been used.
20
CHAPTER 4
RESULTS
4.1 Fishing gears used for shrimp post larvae collection in the Pasur river
A) Stationary gear
Set bag net (locally called Net jal or Behundi jal) is shaped like a small trawl
and is set at a fixed place against current in the Pasur river. When water is
continuously filtered, shrimp post larvae are caught. This gear consists of two
guides with a conical shaped bag net. Around the edges of the opening and
along the edges of the guides a synthetic rope is inserted. The front of the gear
is kept open by 2-4 vertically placed bamboo-sticks.
Plate 3: PL collectors using stationary gear (set bag net) in the Pasur river.
B) Mobile gear
Pull net (locally called Baksho jal) is a rectangular one. It is pulled in knee to
waist-deep water. The nets scrape the bottom and shrimp PL are caught and
concentrated in the end of the net.
21
Plate 4: PL collector using mobile gear (pull net) in the Pasur river.
In the study area, it was found that two types of nets are mainly used for
shrimp post larvae collection in the Pasur river, the pull net and set bag net. The
set bag net accounts for about 60-70% of total catch and represented 95% of the
total nets. The post larvae of shrimp are widely available during full moon
when number of shrimp post larvae in surface layer is the highest.
A series of set bag nets were fixed across the Pasur river. Each net was usually
operated by a single fisher from a boat. Only men were involved in set bag net
fishing due to laborious work. The set bag net was used in the surface layer
against the tidal water in the river. Fishers operated their nets twice a day
during two high tides. Conversely, pull nets were operated once a day during
low tide. A pull net was operated by a single fisher without a boat. Usually
women and children were involved in the pull net fishing. Pull net is pulled in
the surface layer against the tidal water in shallow parts along river banks. The
comparison of shrimp post larvae collection by pull net and set bag net in the
Pasur river is shown in Table 1.
22
Table 1: Comparison of shrimp post larvae collection by pull net and set bag
net in the Pasur river during the study period.
Fishing information
Pull net
Set bag net
Fishing area
Surface layer, shallow Surface
layer,
water
water
Net operation
Without boat
With boat
Length of net (m)
1.5-2
10-15
Width of net (m)
2-2.5
2-4
Mesh size (mm)
2-3
1.5-2.5
Fishing operation
During low tide
During high tide
Net
hauling
interval 40-60
deep
20-25
(min)
For shrimp PL collection in the Pasur river the pull net was found to be very
common. Mainly female and children used pull net because of its low cost.
Again, a large portion of fishers used set bag net (Net jal or Behundi jal) but only
male were involved in this operation. In the study area, it was found that 56%
PL fishers used pull net and 44% PL fishers used set bag net.
The types of net used by PL collectors in the study area of the Pasur river are
presented in Figure 3.
23
Pull net
Set bag net
44%
56%
Figure 3: Net used by the PL fishers of the Pasur river during MarchNovember, 2013.
4.2 Collection of shrimp post larvae (PL)
Shrimp post larvae collection is a very common practice in the Pasur river.
Fishermen collect PL depending on low and high tide. PL moves with the water
current. During high tide PL moves upstream and during low tide,
downstream. Fishermen used set bag net for PL collection during high tide and
pull net during low tide.
4.2.1 Variation of PL caught by set bag net fisher and pull net fisher
There were two main gears used to catch shrimp PL: set bag net and pull net.
The catch of set bag net was higher than pull net. The fishers reported that out
of total catch, 70% was by set bag net and 30% by pull net (Table 2).
24
Table 2: Variation of PL caught by set bag net fisher and pull net fisher in the
Pasur river.
Month
No. of PL
No. of PL
No. of PL
No. of PL
caught by
caught by
caught by
caught by
set bag net
set bag net
pull net
pull net
fisher/day
fisher/month
fisher/day
fisher/month
January
-
-
-
-
February
-
-
-
-
March
133
3990
57
1710
April
143
4305
62
1845
May
169
5061
72
2169
June
211
6321
90
2709
July
195
5838
83
2502
August
165
4935
70
2115
September
130
3885
55
1665
October
115
3444
49
1476
November
99
2982
43
1278
December
-
-
-
-
4.2.2 Catch of shrimp PL and income of a fisher family (3-4 members)
During the study period, the post larvae of shrimp were available for 9 months,
from March to November. The peak period was found during April to August.
The highest catch found in the month of June and the lowest catch in November
(Table 3).
Fishers sold their post larvae to the local fry traders or at the coastal markets in
Mongla; the market chain from fishers to farmers passes through a number of
intermediaries: transporters, suppliers, fry traders, and local agents. In the
study area, it was found that the highest price ( Tk. 3.00) of a single PL was
25
observed in May, which was followed by April and March representing Tk.
2.80, Tk. 2.60 respectively; the lowest price (Tk. 0.90) in November (Table 3).
It was found that the highest income (Tk. 22575) of a fisher family (3-4
members) was in June and the lowest income (Tk. 3834) was in November
(Table 3).
Table 3: Catch of shrimp PL and income of a fisher family (3-4 members).
Month
No. of PL
No. of PL
Total catch
of
PL/month
in the
study area
collected/
collected/
day
month
January
-
-
-
-
-
Income
(Tk.)/
month
of PL fishers
in the study
area
-
February
-
-
-
-
-
-
March
190
5700
1710000
2.60
14820
4446000
April
205
6150
1845000
2.80
17220
5166000
May
241
7230
2169000
3.00
21690
6507000
June
301
9030
2709000
2.50
22575
6772500
July
278
8340
2502000
2.30
19182
5754600
August
235
7050
2115000
1.90
13395
4018500
September
185
5550
1665000
1.30
7215
2164500
October
164
4920
1476000
1.00
4920
1476000
November
142
4260
1278000
0.90
3834
1150200
December
-
-
-
-
-
-
26
Price
Income
(Tk.)/PL
(Tk.)
/month
4.2.3 Timing of shrimp post larvae collection
The PL fishers in the study area of the Pasur river collected post larvae mainly
at day but during peak season some PL fisher also collected at night. It was
found that during peak season 75% PL fishers collected their PL at both day and
night; 25% only at night.
4.3 Impact on the environment
4.3.1 Decreasing trends of shrimp PL availability in the Pasur river
According to PL collectors and local people, the post larvae of shrimp were
abundant in past years and it has been decreased year after year. The present
study observed that various number of factors were responsible for reduced
availability of shrimp PL, for example, over collection of larvae, the use of
habitat-destructive gear, uncontrolled fishing of shrimp broodstock, water
pollution (mainly industrial waste and oil pollution), poison fishing, the
destruction of mangrove forests, river erosion and also violation of fishing rules
over peak season of PL collection.
4.3.2 By-catch species caught during shrimp PL collection in the Pasur river
The most common, commercially important by-catch species discarded from
the harvesting of wild shrimp post larvae in the study area of the Pasur river
are shown in Table 4.
27
Table 4: By-catch species caught for a single shrimp PL during PL collection
in the Pasur river.
Local name
English name
Scientific name
By-catch By-catch
in
in
set bag
Pull net
net
Bagtara chingri
Green tiger prawn
Penaeus semisulcutes
25
10
Chaka chingri
Indian white prawn
P. indicus
18
7
Bagha chingri
Banana prawn
P. merguiensis
14
6
Horina chingri
Speckled shrimp
Metapenaeus
18
7
monoceros
Honni chingri
Yellow shrimp
M. brevicornis
14
6
Chotka icha
Birma river prawn
Macrobrachium
14
6
malcolmsonii
Kathali icha
Riceland prawn
M. lanchesteri
16
6
Dimua icha
Dimua river prawn
M. villosimanus
12
5
Lutia icha
Shortleg river prawn
M. mirabile
11
6
Thengua icha
Freshwater prawn
M. birmanicus
12
5
Goda icha
Hairy river prawn
M. rude
15
6
Kaira icha
Kaira river prawn
M. dayanum
11
4
Vetki
Sea bass
Lates calcarifer
14
6
Chapila
Indian river shad
Gudusia chapra
18
7
Tengra
Stripped dwarf catfish Mystus spp.
25
10
Loitta
Bombay duck
Harpadon nehereus
13
5
Baila
Tank goby
Glossogobius spp.
26
11
Baim
Zig-zag eel
Mastacembelus
25
10
armatus
Boal
Wallago
Wallago attu
5
2
Puti
Puntius barb
Puntius spp.
28
12
28
4.3.3 Amount of by-catch for each shrimp post larva collection in the Pasur
river
The majority of fishers reported that PL collection is not harmful to the
environment. Their argument was that they have been fishing for larvae year
after year. Some other respondents acknowledged that fishing for shrimp larvae
could have a negative impact on the environment mainly due to by-catch.
Discarded by-catch has also been the main argument behind the ban on larvae
collection. During the study, it was found that the by-catch rate was high in
shrimp larvae fishing as very fine mesh (1.5 mm) nets were used (although the
government earlier allowed a minimum 30 mm mesh). As a result, a huge
number of fish and other crustacean larvae and juveniles were caught and later
discarded on land. The set bag net was responsible for higher by-catch than the
pull net. According to the survey, a set bag net fisher caught 334 non-target fry
for each shrimp post larva collection, while this figure was 137 in case of pull
net. Total amount of by-catch for each shrimp post larva collection in the Pasur
river is shown in Table 5.
Table 5: Total amount of by-catch for each shrimp post larva collection in the
Pasur river.
By-catch
By-catch in set bag net
By-catch in pull net
Shrimp and other prawn
180
74
Fishes
154
63
Total
334
137
4.3.4 Decreasing trends of by-catch species during shrimp PL collection
The study revealed that a large number of by-catch species (Table 4) especially
finfish, shrimp and other prawn were abundant in the Pasur river before few
years. But this availability has been narrowed because of indiscriminate
catching of wild shrimp PL with heavyweight by-catch which thrown on dry
land after separating shrimp PL or taken for family consumption. Other reasons
include coastal pollution, overfishing, catching of undersize fish etc.
29
4.4 Socioeconomic status of PL fishers
4.4.1 Training on wild shrimp PL collection
It was found that 55% PL fishers have training on one or more than one related
matter but 45% did not take part in any training programme. In different time,
some NGOs (CARE, BRAC) arranged training programme and provided
necessary PL collection tools. In the training programme, they suggested that
by-catch species have to release in water body after separating targeted shrimp
PL and also raised awareness about probable negative impact on indiscriminate
wild post larvae collection.
4.4.2 Residential migration of shrimp PL collectors
Shrimp post larvae collection is a seasonal activity. During PL collection period,
many fishers family migrated from their residence. The present study found
that 60% were migrated family whereas 40% were local. The migrated were
from Barisal, Khulna, Patuakhali and Bhola.
4.4.3 Experience of PL fishers in the Pasur river
It was found that 58% fishers were involved for 2-5 years, 24% fishers for 6-8
years, 8% fishers for 1 year, 4% fishers for more than 8 years with PL collection
but newly recruited fishers were only 6% (Figure 4).
30
60
% of fishers
50
40
30
20
10
0
1st Year
1 Year
2-5 Years
6-8 Years
8 Years+
Years
Figure 4: Experience of PL fishers in the Pasur river.
4.4.4 Time spent by the PL fishers
84% were full time fishers and 16% were part time fishers (Figure 5).
Full time
Part time
16%
84%
Figure 5: Time spent by the fishers in the Pasur river.
4.4.5 Investment during PL collection period per year
According to PL fishers information, investment is needed mainly for buying
collection tool and also repairing net, boat etc. The present study found that
36% PL fishers invested Tk. 4001-5000, 28% fishers invested Tk. 5001-6000, 16%
31
fishers invested Tk. 3001-4000, 14% fishers invested Tk. 6001-7000 and 6%
fishers invested Tk. 2001-3000 (Figure 6).
40
% of fishers
35
30
25
20
15
10
5
0
2001-3000 3001-4000 4001-5000 5001-6000 6001-7000
Taka
Figure 6: Investment by PL fishers during collection period per year in the
Pasur river.
4.4.6 Types of PL fishers
Fishers were categorized into two groups. They were: i) Professional fishers,
who depend on post larvae fishing almost year round for their livelihood, and
ii) Subsistence fisher, who used to catch PL for part time earnings only. It was
found that 90% fishers were professional and other 10% were subsistence PL
fishers (Figure 7).
32
Professional PL fisher
Subsistence PL fisher
10%
90%
Figure 7: Types of PL fishers of the Pasur river.
4.4.7 Age structure of PL fishers
It appears (Figure 8) that age group of 32 to 42 years was the highest (34%) and
less than 20 years was the lowest (8%). It was found that 26% of the fishermen
were 21 to 31 years group, 22% were 43 to 49 years group and 10% were in
above 50 years age group.
35
% of fishers
30
25
20
15
10
5
0
<20 Years
21-31
Years
32-42
Years
43-49
Years
>50 Years
Age groups
Figure 8: Age structure of PL fishers of the Pasur river.
33
4.4.8 Income of PL fishers other than fishing
20% fishers were involved in agriculture as alternative occupation, 34% fishers
in day labour, 24% van driving, 10% boat driving, 6% fishers in business, 4%
fishers in poultry farming and remained 2% fishers in other occupation (Figure
9).
Agriculture
Labour
Van driving
Boat driving
Business
Poultry farming
Others
2%
6%
4%
20%
10%
24%
34%
Figure 9: Income of PL fishers other than fishing.
34
CHAPTER 5
DISCUSSION
5.1 Fishing gears used for shrimp post larvae collection in the Pasur river
It was found that two types of nets were used for shrimp post larvae collection
in the Pasur river, pull net and set bag net (Net jal or Behundi jal). 56% fishers
were found to be used pull net and 44% set bag net. In the Pasur river, shrimp
post larvae collection was a seasonal activity that takes place from March to
November and the peak period was April to August. During the rest period of
the year, fishers are involved in other types of fishing, including other shrimp,
hilsa and finfish fishing (Ahmed et al., 2013).
During the study, it was found that pull net was operated by a single fisher; the
length of pull net varies from 1.5 to 2 m, and the width varies from 2 to 2.5 m. A
pull net is pulled in the surface layer against the tidal water in shallow areas
along the river banks. A pull net is also used close to the shoreline since it is
fixed to the bottom by a bamboo pole. Usually, fishers operate this net for one
half of the day during low tide. During operation, the net was emptied at 4 to 6
min intervals. Fishers kept all the larvae in aluminum containers, and separate
the shrimp larvae by using white plate and spoon. All other captured species
were discarded during sorting on the shore (Ahmed and Troell 2010).
Another important gear for PL collection in the Pasur river was set bag net.
Series of set bag nets were fixed across the Pasur river, and each net was usually
operated by a single fisher from a boat. The typical size of set bag net was 10–15
m in length and 2–4 m in width. The set bag net had a rectangular mouth, with
an average size of 5 m. The mouth is kept open by a vertical bamboo pole
fastened to the corners of the upper and lower panels. The set bag net tends to
be used in the surface layer against the tidal water in the deeper part of the
river. During operation, the net was emptied at 20 to 25 min intervals. Fishers
operate their nets twice each day during high tide (Dev, 1998).
35
5.2 Shrimp post larvae (PL) harvesting
Almost all PL larvae fishers in the survey expressed concern about declining
larvae catches in the study area. The highest catch (301 PL/day/fisher family)
found in the month of June and the lowest catch (142 PL/day/fisher family) in
November. The catch of shrimp larvae has declined gradually over the last 5
years. It was observed that various number of factors were responsible for
reduced availability of shrimp PL, for example, over collection of larvae, the use
of habitat-destructive gear, uncontrolled fishing of shrimp broodstock, water
pollution (mainly industrial waste and oil pollution), poison fishing, the
destruction of mangrove forests, river erosion and also violation of fishing rules
over peak season of PL collection. This study was similar to the findings of
Ahmed and Troell (2010).
In the study area, it was found that the highest price (Tk. 3.00) of a single PL
was observed in May, which was followed by April and March representing Tk.
2.80, Tk. 2.60 respectively; the lowest price (Tk. 0.90) in November. During
winter season from December to February, shrimp PL were not collected due to
unavailability of shrimp post larvae in the river.
5.3 Impact on the environment
Some of the fishers believed that shrimp post larvae (PL) collection is not
harmful to the environment. Their argument was that they have been fishing
for larvae year after year. Again, most of the fishers acknowledged that fishing
for shrimp larvae could have a negative impact on the environment mainly due
to by-catch. Discarded by catch has also been the main argument behind the
ban on larvae collection (DoF, 2002). The by-catch rate is high in shrimp larvae
fishing as very fine mesh (1.5 mm) nets are used (although the government
earlier allowed a minimum 30 mm mesh). As a result, a huge number of fish
and other crustacean larvae and juveniles are caught and later discarded on
land. Negative environmental impacts from shrimp larvae fishing are mainly
associated with by-catch, which may cause declines in capture fisheries and in
overall biodiversity. Intensive fishing can also result in the physical destruction
36
of nursery grounds, decreased shrimp brood stock, the prevention of fish
migration, and reduced wildlife.
In the present study, it was found that a set bag net fisher catches an average
334 of non-target fry for each shrimp post larvae, while this figure was 137 in
case of pull net. Some studies also reported that in the harvesting of single
shrimp PL, over 1000 non-target fin and shellfish larvae are destroyed in the
process (Ahmed et al., 2010). Further, several studies have shown that the
amount of by-catch from the harvesting of wild shrimp PL is the highest of any
fishery in the world and it was estimated that over 98 billion of larvae and
zooplankton are discarded every year, globally (EJF, 2004; FAO, 2001; Latif et
al., 2002), calculating to about 35,000-50,000 ton of discarded by-catch every
year (DoF, 2002; Islam, 2003). Capture fisheries fishing for shrimp post larvae
results in by-catch of commercially important species groups. The most
common, commercially important by-catch species discarded from the
harvesting of wild shrimp PL in the coastal zones of Bangladesh (especially in
the Pasur river) are: (1) shrimp-white shrimp (Penaeus indicus), shrimp (P.
merguiensis), shrimp (Metapenaeus monoceros); (2) prawn- monsoon river prawn
(Macrobrachium malcolmsonii), freshwater prawn (M. villosimanus), freshwater
prawn (M. mirabilis), freshwater prawn (M. birmanicus), freshwater prawn (M.
rude), freshwater prawn (M. dayanus) and (3) fish- hilsa shad (Tenualosa ilisha),
Indian river shad (Gudusia chapra), sea bass (Lates calcarifer), loita (Harpadon
nehereus), tengra (Mystus spp.), punti (Puntius spp.), baila (Glossogobius spp.),
boal (Wallago attu) etc. Larvae fishers, who are also involved in capture
fisheries, expressed concern over declining catches of prawns, shrimp, and fish.
Furthermore, indiscriminate harvesting of wild shrimp PL presented a critical
threat to endangered or threatened species of the Pasur river, therefore
hampering the global efforts on conservation and maintenance of biodiversity.
During the present study it was observed that not only finfish larvae are
discarded, but different shellfish and crustaceans are also indiscriminately
exploited along with targeted shrimp larvae. Besides the many fish species, the
37
brackish water supports many species of shrimp and prawns with high
ecological and commercial values. The black tiger shrimp (P. monodon) stands
out in terms of its commercial importance and availability. PL fishers reported
that the availability of wild shrimp has gradually declined during the last five
years. The excessive removal of ecologically important species may lead to
serious problems for long-term fisheries development in the Pasur river,
including the Sundarbans.
5.4 Socioeconomic status of PL fishers
In the present study, it was found that two types of shrimp post larvae fishers
were identified in the Pasur river as professional PL fisher and subsistence PL
fisher which was more or less similar to the findings of Shahriar et al. (2009).
The present study revealed that 58% fishers were involved for 2 to 5 years, 24%
fishers for 6 to 8 years, 8% fishers for 1 year, 4% fishers for more than 8 years
with PL fishing but newly recruited fishers were only 6%.
Most of the fishers of the Pasur river were involved in PL fishing as their main
occupation. However some were also engaged in agriculture, day labour, van
driving, boat driving, business and poultry farming as alternative occupation.
This information is similar to the findings of Alam et al. (2009).
The present study showed that the highest income (Tk. 22575) of a fisher family
(3-4 members) was in June and the lowest income (Tk. 3834) was in November.
5.4.1 Children and women involvement in post larvae collection
Poverty necessitates that parents send their children to collect shrimp post
larvae. Although they sometimes start out as a hobby, or fun, it ends up as a
compulsory occupation against their will. Child PL collectors have fairly
flexible working hours. Off-season, these hours are usually short enough to
enable children to also attend school. Often children who collect PL are
prevented from attending school regularly because shrimp PL collection clashes
with school hours. The parents are mostly illiterate and they are not fully aware
38
of the benefits of sending their children to schools. They see only the earnings of
their children, which helps the family survive.
The atmosphere of violence created by shrimp farming has particularly
negative consequences for females. Guards of shrimp farms, usually from
outside the local area, reportedly harass and mistreat women and girls as they
walk along village roads. Women often work at night in the depot or catch
shrimp post larvae when shrimp PL presence is increased by high tides.
Plate 5: Children in PL collection in the Pasur river during the study period.
39
Plate 6: Women in PL collection in the Pasur river during the study period.
40
CHAPTER 6
CONCLUSIONS
The present study was conducted to know the present status and assess the
environmental impact of PL collection on other aquatic species using
questionnaire interview with PL collectors and fry traders in the Pasur river
adjacent to Mongla upazilla under Bagerhat district, a coastal area of the Bay of
Bengal, situated in the southwest part of Bangladesh. The study was conducted
from January 2013 to December 2013. The collected data were summarized,
tabulated and analyzed according to the objectives of the study. The highest
catch (301 PL/day/fisher family) found in the month of June and the lowest
catch (142 PL/day/fisher family) in November. The present study observed
that the practice of fishing wild post larvae had an impact on other finfish or
shrimp resources, as a large number of finfish and lesser valued shrimps
accidentally harvested along with the valuable post larvae of shrimp and prawn
may be subsequently destroyed. The natural stock of post larvae might also be
seriously affected by prawn and shrimp farming itself. There was a huge ‘bycatch’ associated with intensive fishing for PL in the Pasur river. ‘By-catch’ for
a single shrimp PL were about 254 post larvae of shrimp and prawn, 217 post
larvae of fish and many other aquatic animals. The present study showed that
fish and crustacean availability was decreasing due to over fishing of shrimp
PL. To minimize the dependency on wild post larvae collection and to save the
aquatic biodiversity as well as the environment it is recommended that there is
an urgent need to increase hatchery production of prawn and shrimp PL in
South West Bangladesh. More in-depth studies are required on catch
composition and survival rates of ‘by-catch’. Moreover, to conserve the
biological diversity of the aquatic environment, as well as to maintain
sustainable fishery resources, it is also recommended that: immediate measures
be taken to release the entire by-catch back to their habitat after sorting post
larvae of shrimp; a ban on seed collection from July to December be imposed;
41
and dependency on wild seeds be reduced by establishing more shrimp
hatcheries.
During the time of data collection the researcher encountered the following
methodological problems:
i.
Most of the fishers in the area had no concept about research work and it
was therefore, difficult to explain the purpose of this research to
convince them;
ii.
Most of the PL collectors were initially in hesitation to give answer of the
questions;
iii.
Most of the fishers were not interested to give accurate cost, investment
and catch rate;
iv.
The respondents were not maintaining any written records of their
fishing activities;
v.
Sometimes they provided misleading information that caused wide
variation between the collected information and the actual figure. For
overcoming these problems, attention was given during data collection
by using several data collection methods.
42
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