Md. Giasuddin Khan
Principal Scientific Officer,
Bangladesh possess a typical tropical multi-species fisheries ecosystem. One single operation of any type of fishing gear in any fishing area brings in a number of species of various sizes and ages. It also has the complexity of multigear fisheries system making the situation further complex for management and conservation of the resources for sustainable use.
Increasing pressure on the coastal resources has caused decline of many of the marine fish and shrimp stocks. The general belief that the continental shelf of Bangladesh is a treasure of fish for unlimited exploitation, has led to a production oriented strategy and thus resulted in some cases overexploitation of resources. The management of the EEZ is also very complex.
For last two decades a few surveys were undertaken to give a wide range of estimates. Of these, the report by West (1973), giving 3,73,000 mt of demersal fish stock and 9,000 mt. of penaeid shrimp stock is important for various reasons, although it was an over estimate according to some authors (Saetre 1981; Penn, 1983; White and Khan 1985; Vanzanlinge 1988 and Khan et al. 1989). It created lot of interest and courage for investment in the trawling industry. The MITA-JVA survey (1976–77) further accelerated deep sea fishing interest as it reported the presence of abundant shrimp stock for exploitation.
Based on recent surveys, however, involving R.V. Dr. Fridtj of Nansen (FAO/BGD 1979–80) and R.V. Anusandhani (BGD 1983 and FAO/BGD 1984–86) (Saetre, 1981), (Khan et al., 1983) and (Lamboeuf, 1987) give demersal standing stock estimates between 1,50,000–1,60,00 mt at the exploitation phase. The shrimp stock was reported within 2000–4000 mt by different authors (Penn, 1983; White and Khan, 1985; Mustafa et al. 1985). Khan et al. (1989) have taken the biological parameters into account to estimate an annual 7000–8000 mt harvestable penaeid shrimp stocks.
The pelagic resources survey is yet to take place to give a reliable estimate of the standing stock. Acoustic survey by Dr. Fridtj of Nansen however, gave an estimate of 60,000–1,20,000 mt. According to Saetre (1981) this is under-estimated. Stock assessment studies were undertaken by DOF Marine Survey Wing recently with the technical assistance of FAO/BOBP. The results of these have been reflected in the following chapters.
Fishing Gear Population and Areas of Operation
The number of fishing gears/crafts engaged in different fisheries is furnished (Table 1).
The ESBN fishery is spread throughout the channels, canals, tributaries and estuaries of the country in Brackishwater environment. This gear is operated mostly within 10 m depth line throughout the year. Marine set bagnet is larger than ESBN and is operated at around 20 m depth seasonally in winter at selected areas such as down Sonadia Island, Dubla island and Mohipur (Patuakhali).
Trammel nets are operated at Teknaf -Cox's Bazar Coast only at 5–15 m depth, rarely deeper. Beach seine are operated almost everywhere with 62% at Cox's Bazar region alone. In the estuary they are operated during March-November period.
The shrimp fry collecting gears are widely spread in the estuaries, river mouth and in the sea coast except in Noakhali region. Bottom long line is operated within 30 m depth off Cox's Bazar region. The drift gill nets are operated from all coastal districts within 40 m depth for pelagic species eg. hilsa.
Total production of marine fisheries in terms of landing from all gears/crafts was estimated to be 2,64,000 mt. The drift gill net fishery and estuarine set bagnet fishery take the major bulk of the production, followed by the marine set bagnet fishery and trawl fishery accounting to 1,36,000 mt, 73,000 mt, 26,000 mt and 17,000 mt, respectively.
The major species caught by each gear are as follows: Among the penaeid shrimp, the trawler fleet accounts for 76.9% of brown, 15.7% of tiger, 1.9% of white and 2% of pink and 3.5% of mixed small shrimp (Khan et al., 1989). The trawl production of penaeid shrimp on the basis of commercial data appears to be an underestimate due to under reporting and various others reasons. Actual estimate would be much higher than that. On the other hand, the shrimp trawlers throw away the major part of the white fish as trash which would be in the tune of 35,000–40,000 mt annually (White and Khan, 1985).
Maximum sustainable yield (MSY) and Maximum Economic Yield (MEY)
Surplus production model of Schaelfer (1954) was used to estimate MSY for shrimps based on the catch and effort data from the commercial trawlers. The MSY values obtained for penaeid shrimps were 4000, and 4500 mt and the effort level required to achieve this was estimated to be within 8500 and 9000 standard fishing days. The results indicate that the fishing effort of the Trawl Fishery was above the optimum effort level during 1983–84 and 1984–85 period. The present effort is however the optimum effort for MSY.
Schaeffer type economic yield model was also obtained. The maximum economic yield level and the corresponding effort level were estimated from the plot. The maximum economic yield appears to be realized when the fishing effort is around 7000 boat days which was optimum during 1985–86 to 1988–89 period but had fallen below during that in recent years. The MSY effort level is about 28% greater than the MEY fishing effort. It appears that shrimp trawling has generally been swinging between the MSY and MEY except in recent years.
The Problem of Multispecies and Multigear Fisheries Ecosystem
In the coast of Bangladesh, particularly in the shallow water artisanal and offshore demersal fisheries, different sizes and varieties of species are caught. This makes selective fishing and conservation strategy very much complex. In addition to this a single species of the same stock is caught by a number of gears at different sizes which adds to the management complexity.
Controlling any one fishing gear or craft leaves the others free to overfish the same stock. A coordinated effort needs to be made for the entire fishery, with particular attention to juvenile harvesters.
Status of Exploitation
Due to multispecies problem any fishing gear does not exploit all the species at the same rate or degree, and any single species is not exploited by all the gears at same rate. The rates of exploitation on different species by different gears are very much different. This is mainly for two reasons, one is excessive effort and the other is the age/length at first capture which is area specific.
Brackishwater estuaries are the meeting points of the fauna from three different ecosystems. Brackishwater species live, grow and spawn in the same environment; the marine fauna use the brackishwater area as nursery ground and visit for a short time, some fresh water fauna e.g., M. rosenbergii & P. styliferus visit estuary for either spawning or nursing. Fishing is very intensive in this area and set bagnet is the most extensive capture fishery.
Almost all the marine and fresh water animals are over exploited, majority of them very seriously by the estuarine set bag net, while the brackishwater species are either under exploited or exploited at optimum level.
Dynamics of Population of Selected Species
It has been seen that P. monodon is most exploited by ESBN and push net (Larval fishery). Over two billion post larvae (1–2 cm) are removed annually by the larval fishery. The BOBP estimate indicate that population size at this stage was 33 billion. ESBN takes the largest population (one fourth of larval catch) followed by the trawl fishery while the other gears take relatively negligible numbers.
M. monoceros appears in the larval gears as by catch and the number produced is relatively small. BOBP estimate show that the larval population at this stage (around 1.5 cm) is 3560 million. Larval fishery takes 20% of this population. The size of the population at three cm size entering the ESBN fishery would be around 2190 million.
Larval fishery exploited 10,706 million P. indices (white shrimp) larvae which is almost five times for the catch of the target species. This species appears to have the largest population among the penaeid shrimps at birth but the total production, particularly in the trawl fishery is relatively very low despite of higher effort by trawl. This is because of its poor availability in deep water. They are very much vulnerable to trammel net fishery due to area preference.
Comparison of Yield And Revenue Per Recruit
Beverton and Holt's yield per recruit analysis was attempted to choose the optimum size at first capture for the best yield per recruit keeping the effort level constant but changing the size at first capture, since it is different in each fishery. It was found that, Penaeus monodon for example, the maximum yield was achievable at an Lc size which lies around the exploited size by trammel fishery.
The maximum gain in YPR by trammel net and trawl net over that of ESBN were about 20% and 14% for P. monodon and 37.5% and 31.20% for M. monoceros respectively, but it has been seen that the maximum gain in revenue per recruit were 146% and 128% for P. monodon and 600% and 550% for M. monoceros respectively. It is evident that catching very young animals is not only harmful from the yield point of view, but much more harmful from the revenue concept.
Economic Analysis Pertaining To Sustainable Development
Having found the positive indication in the result of the yield and revenue per recruit, further analysis was carried out with the same set of data with additional information support for analysis of ‘Thompson and Bell’. The concept of the study was to find a comparative economic gain from different fisheries if only one is allowed to operate and all other fisheries are suppressed, or if only ESBN is suppressed and others allowed to stay as it is.
From this study the shrimp seed fishery (pushnet etc) was excluded. Because in the push net catch the range of length of the species under consideration were so small that estimation of mortality was not permitted by the data, which was required for the Thompson and Bell analysis.
It has been seen that even if the larval fishery is allowed to operate at the present rate and if only the trawl fishery is kept and all other interactive fisheries was suppressed there would be substantial gain in weight to give about 300% gain in value of the catch, but about 250% gain in value of the catch if only ESBN fishery is not in operation.
On the other hand trammel net shows an extremely high gain, of about ten times the value of yield when all other fisheries (including trawlers) are suppressed, but a small gain in yield and large gain in value (300% if only ESBN is suppressed). So from different analyses it is evident that withdrawal of ESBN fishery will be necessary for resources conservation as well as for substantial economic benefit of country.
Scope For Expansion of Trammel Net Fishery
At present the trammel net fishery is in operation in the Teknaf-Cox's Bazar coast only. The reason for this is not that this gear is not suitable for other areas, but the fact is that this gear has entered into Bangladesh from Burma through the Teknaf coast and was introduced by the fisherman only on that coast. Expansion of this gear in the western coasts would need feasibility demonstration and extension to the fisherfolk.
Presently, this gear is operated only within 15 meter depth of water hardly beyond that limit. Because they are operated by country row boats and since it is a single day fishing operation they can not go any far. Mechanization of the boats and technological improvement of the gear may help to extend it vertically up to 40 m depth of water, which (at the bottom) is not presently occupied by any type of gear. Some marine behunds however are operated in selected places only and not beyond 30 m depth. But experimentation of the technology and feasibility would be necessary for such expansion. Such a project is going on in India.
Rehabilitation of ESBN Fisherfolk Vis-vis Their Socioeconomic Condition
Very few of the behundi fisherman are familiar with any other profession within or outside fishery sector. These fishermen are very poor and lack education. They have no idea at all about the dynamics of the resources and concept of the management.
About 69% of the behundi fisherfolk are illiterate, and the percentage of illiterate women is still higher. Literacy here only means primary schooling. They live in unhygienic conditions without proper drinking water and sanitation facility. 32% of the households are solely dependant on ESBN, 62% combine other fishery or non fishing activities, and 11% are labour households in the village surveyed. This is a family oriented enterprise, they do not know anything else but to go to set their net irrespective of availability of catch or not.
In the Cox's Bazar area the catch is comparatively high, as much as seven times and 92% fishermen of this area live above the poverty level, having an average income of Tk. 1,00,000 per annum. They also suffer from natural calamities.
These fisherfolk need rehabilitation firstly for conservation of the resources. Secondly, this traditional gear is expensive but not very remunerative. This makes them poorer day by day. Some intervention is necessary to motivate them to shift to other gears or other professions as might be suitable for them as well as for the country. Horizontal and vertical expansion of the trammel net fishery may be one alternative. An extension program followed by credit support for the ESBN fisherfolk deserves consideration.
A limited expansion of the BLL and MSBN may also help initial shifting. It has been found that technological improvement of ESBN and mesh size increase would not enhance income because the gear is operated on the nursery ground only, where and big fishes are not available for harvesting.
Area and Seasonal Restriction of ESBN Fishery
Since the ESBN fishery involves 55,000 fishermen and 1,50,000 dependants, it would not be easy to withdraw the nets at one stroke, leading such a big community to starvation. It appears that area and season closure would help substantially for the time being.
Since 46% of ESBN production comes from one single stratum i.e. Cox's Bazar Zone. Regulation of the fishery in this single stratum itself could contribute to significant impact on conservation of the resources of the major valuable species.
Length modal progression and the peak season for catch rates in ESBN (such as July to September and to a slightly lesser extent during February to April), show that regulating the operation of ESBN during these periods even in the single stratum may be valuable as well as possible. The income of ESBN fishermen in this stratum is at least three times more than in any other strata and they live much above the poverty level. They also have alternate sources of income and they live close to the trammel and bottom long line fishing ares. Many of them are familiar with those methods of fishing. So transferring some of these fisherfolk to trammel netting and long lining would be much easier and feasible than those of the other stratum.
Conflict of Interest in Resource Management
The coastal aquaculture for tiger shrimp has so far used about 1,15,000 hectares of land. Almost the whole industry (99%) is now dependant on the wild source for seed supply. More than 200 crores of tiger shrimp post-larvae and another 20,000 crores of other fauna which have no commercial value at all are harvested to support shrimp farming.
Intensification of culture systems, for will demand at least 10 times the quantity of seed. For this, the farmers have to further depend on the natural source in absence of commercial hatcheries. This requires serious consideration. It is important that the expansion of semi-intensive culture system should be commensurate with the hatchery development. Further intensification of wild seed collection will create very serious adverse effects on biodiversity and on marine and estuarine fish stocks.
Diversification of Interest For Development
Where there is a strong and increasing competition in the demersal and shrimp trawling and coastal aquaculture but the pelagic resources like tunas, skipjacks, sharks etc. have remained untapped. The main reason for this is the lack of technology for exploration and exploitation of these resources. Stock assessment and technological and financial feasibility studies are necessary. The pelagic fishery may be developed with smaller Srilankan type boats. New entry to such endeavours may be limited except the ESBN fisherfolk who need to be encouraged.
Also, gradual change over of the shrimp boats to fin fish boats would help landing of the presently discarded fish.
Awareness Building among the Artisanal Fisherfolk
Only regulations are not effective for management of fisheries. Participation of all stake holders, and the fisherman in particular, is vitally important for an effective “community based management”. For such participation fishermen need be educated and motivated. They need to be aware of the resource dynamics and negative and positive aspects of fishing. For this a detailed extension programme need be undertaken immediately. This will go a long way to help sustain the marine fisheries resource, with active participation of the fishermen.
Anonymous, 1984–85. Survey result of the frame survey of the marine artisanal fisheries. Department of Fisheries, Bangladesh.
Chowdhury, Z.A. 1987. Studies on the year roundBehundi net catch composition in the Moheshkhali Channel. (Dec, 1984-Nov, 1985). Marine Fisheries Survey Management and Development Project, Cox's Bazar. Mimeo. 5pp.
Dutta, k.k. and S.S. Dan, 1988. Comparative efficiency of different type of set bag net (Behundi jal) units of West Bengal. Sea food export journal, August, 1988 issue, pp-5–14.
Edeson, W.R. 1979. Legal & institutional aspects of the management of fisheries in the Bangladesh Exclusive Economic Zone. FAO/UNDP, Indian Ocean Programme. 10P/Tech/79/32 : 54p.
Islam, S. and Khan M.G. 1993. The Trammelnet fishery. Studies of interactive Marine Fisheries of Bangladesh. BOBP/WP/89.
Islam, S., Khan M.G., Quayun, S.A., Sada, N.N.U., and Chowdhury, Z.A. 1993. The Estuarine Set bagnet Fishery. Studies of interactive Marine Fisheries of Bangladesh. BOBP/WP89.
Khan M.G., Mustafa, M.G., Sada, N.N.U. and Chowdhury, Z.A. 1989. Bangladesh off-shore marine fisheries resources studies with special reference to the penaeid shrimp stocks, 1988–89, Marine Fisheries Survey, Management & Dev. Project, Department of fisheries, Government of Bangladesh, Chittagong, October, 1989. 213p.
Khan, M.G. and Haque K.A. 1988. Exploration and Exploitation of the Marine Fishery Resources of Bangladesh. J. NOAMI, Vol.5, No.1 & 2, 1–5 pp.
Khan, M.G. 1987. Some aspects of population dynamics of the brown shrimp Metapaeneus monoceros (Fabricus, 1878) of Bangladesh Coast, Compilation of reports on the marine Fisheries Survey and Research: Marine Fisheries Research, Management and Development Project, Chittagong. 291–297 pp.
Lamboeuf, K. 1987. Bangladesh, Demersal resources of the continental shelf. FAO/BGD Marine Fisheries Research, Management & Dev. Project, FI: DP/BGD/80/015: 26p.
Mustafa, M.G., Khan, M.G. and Humayun, N. 1987. Bangladesh Bay of Bengal penaed shrimp trawl survey results, R.V. Anusandhani, Nov 1985-Jan 1987. UNDP/FAO/GOB. Marine Fisheries Research, Management an Dev Project, Chittagong 15 p.
Mustafa, M.G. and Khan, M.G. 1988. ELEFAN based population studies of the tiger shrimp Penaeus monodon in the continental shelf of Bangladesh. Bangladesh J. Fish ( Revised sub: Ref. BJF/88/17).
Penn, J.W. 1983. Bangladesh, an assessment of potential yields from the offshore demersal fish and shrimp stocks of Bangladesh water. FAD yield doc. FI: DP/BGD/81/034. Rome 22p.
Pauly, D. 1984 Methods of assessing the marine stocks of Burma, with emphasis on the demersal species. Marine Fisheries Resources Survey and Exploratory Fishing Project. FI: DPBUR/77/003. Field Document 6:22p.
Pillay, T.V.R. and K.K. Ghosh 1962: The set bag net fishery of the Hogly-Matlah estuarine system (West Bengal), Indian Journal of Fishery Vol.9 (Part A) p-71–98.
Rahman, A.K.A. 1992 Coastal Fishery Management in Bangladesh Paper presented at the expert consultation on the development of community based Coastal Fishery system for the Asia and Pacific, Kobe, Japan, June 9–12, 1992.
Saetre, R. 1981. Survey on the marine Resources of Bangladesh. Institute of Marine Research, Bergan; 67p.
West, W.O.B. 1973. Fishery Resources of the upper Bay of Bengal. Indian Ocean Programme. FAO/UNDP/IOFC/DEV/73/28: 42p.
White, T.F. and Khan, M.G., 1985. The marine fishery resources of Bangladesh and their potential for commercial development. National Seminar on Fishery Management and Development in Bangladesh, Dhaka. souvenir: 1–4pp.
Table 1. The number of fishing gears/craft engaged in different fisheries
|Type of fishing||Major Species/Groups exploited||Annual Prod. (MT)||Number of Unit||Area/Depth (M) of operation|
|A. INDUSTRIAL Trawl Fishing|
|a. Shrimp Trawler||Metapenaeus monoceros, Penaeus monodon, P. semisulcatus, P. merguiensis etc.||4661||2314||43||-||40–100|
|b. Fish Trawler||Jewfish, Catfish, Indian Salmon, Shark & Rays, Pomfret||232||9686||11||-||40–100|
|a. Drift gill net||Hilsa ilisha||-||-||-||-||Upto 30.0|
|b. Fixed gill net||Hilsa ilisha||-||-||-||-||8–10.0|
|c. Large mesh drift gillnet||Sharks||-||-||-||-||30.0|
|d. Bottom set gill net||Polynemus indicus (Indian Salmon)||-||-||-||-||South Patches|
|e. Mullet gil net||Grey mullet||-||-||-||-||5.10.0|
|2. Set bag net||Shrimp & Fish|
|a. Estuarine Set Bag net||Brown and Pink shrimp, Bombay duck, Jew fish, Anchovies, Clupeids, Hairtail etc (Mostly juveniles)||72786||-||12561||5–20.0|
|b. Marine Set Bag net||Brown and Pink shrimp, Bombay duck, Anchovies, Clupeids, etc.||26111.00||-||3852||10–30.0|
|c. Large mesh set||Lates Clcarifer (Sea Perch)||-||-||-||10–20.0|
|3. Trammel net||White, Tiger & Brownshrimp, Jewfish, Catfish||1753||-||400||8–20.0|
|4. Bottom long line||Jewfish, (Like Johinus sp. Pennahia sp. Protonebia sp. Otolithoides sp. etc.||2853||300||-||10–30.0|
|5. Beach seine||Small brown and pink shrimp, clupeids, Anchovies, jewfish, Hairtail etc.||8090||-||558||8–10.0|
|6. Ghar Pata Jal||Brown, White & Tiger shrimp etc.||-||-||-||Upto 10.0|
|7. Cast net||Brown, White & Tiger shrimp etc.||-||-||-||Upto 10.0|
|8. Push net||Larvae of P. monodon as a target species which constitutes less tean 1% of the catch||1294 million||-||43596||Upto 10.0|
|9. Fixed Bagnet||-do-||741 million||-||149449||Upto 5.0|
|10. Dragnet||-do-||14 million||-||5925||Upto 2.0|
|Exclu. Shrimp seed production|