ASIA

BANGLADESH

THE IMPACT OF SHRIMP TRAWLING FISHERIES ON LIVING MARINE RESOURCES OF BANGLADESH

by Md. Masudur Rahman (Director (Marine) of the Department of Fisheries, Matshya Bhaban, Ramna, Dhaka-1000; Bangladesh; PABX: 9566103-4/02)

PREFACE

A workshop was held in Rome, Italy from 17 to 19 March 1999 for the National Coordinators of different countries of the world on the impact of shrimp trawling fisheries on living marine resources. Designated National Coordinators attended the workshop from 14 countries. The undersigned presented a country paper for Bangladesh entitled Effects of Shrimp Trawling on Living Marine Aquatic Resources". Detailed discussions were held on the relevant subject and an exchange of views and information among the country delegates took place. On the basis of the results from discussions a guideline was presented for preparation of a National Report for each country. The National Coordinators were assigned the responsibility of preparing the national report based on information available on shrimp trawling in their countries. The report when complete was sent to FAO HQ, Rome, Italy at the specified time. The workshop was organized by the Global Environment Facility (GEF) of the United Nations Environment Programme (UNEP) and the Food and Agriculture Organization (FAO). A global project based on the national reports from different countries may be initiated in the near future under the Global Environment Facility (GEF) of UNEP and FAO, on different issues dealing with the conservation and management of the marine fisheries resources.

During preparation of the national report following the guideline provided at the workshop, a serious problem was encountered due to lack of information on the effect of shrimp trawling on living marine resources in our marine waters. No previous data were available in proper form on the issue.

Understanding the situation all the available reports, literature, cruise reports of the departmental research vessel, available commercial trawl data, etc., were examined and analyzed. Some basic information such as the presence of benthic organisms in the sea bottom and probable damaging effects on them due to trawling were not collected systematically and scientifically. To put the available information into order, the commercial trawler owners, skippers and crews of the trawlers were interviewed. The scientific officers, other marine fishery officers including all the crew members of the departmental research vessel, were also interviewed. Details of the nature and operation techniques of the shrimp and fish trawlers, mechanized and non-mechanized boats including the gear used were studied and recorded.

From the studies it was revealed that the marine fisheries living resources in Bangladesh are seriously affected in many ways due to shrimp trawling. There is also some fishing effort in the marine and estuarine area which damages the marine bio-mass severely. The most detrimental fishing gear among these is the shrimp fry collection gear and the estuarine set bagnet. Details of the adverse effects of these fisheries are also focused on in the report. So far it is observed that the catch rates of most of the species from marine sources are declining. The other damaging activities, which have harmful effects on the living resources, include water pollution like industrial discharge and oil pollution. Lack of proper surveillance and management due to institutional weakness are also considered responsible for the adverse effects on the marine fisheries resources. Due to stock depletion and reduction in catches for the artisanal fisheries multiple problems have emerged, including unemployment for a major group of the coastal fisheries communities living along the coast.

The Marine Fisheries Officers from both the Marine Fisheries Resource Unit and the Marine Fisheries Department, Chittagong, extended their help in preparation of the report and I would like to express my gratefulness to them.

(Md. Masudur Rahman)
Director (Marine)
Department of Fisheries
(23.9.99)

1. INTRODUCTION

Bangladesh is situated at the northern end of the Bay of Bengal between latitude 20o34' and 26 o38' north and 88o01' and 92 o41' east. The country is endowed with vast inland water resources in the form of rivers, flood-plains, ponds, etc., and marine water, the Bay of Bengal, having great fisheries potential. The inland water of Bangladesh is over 4 million hectares. The country has a 710 km long coastline and approximately 1 million hectares of territorial waters extending up to 19 km. The nation's economic zone extends 320 km (200 nm) out to the sea from the baseline. The total marine water area of Bangladesh is about 164 000 km² of which more than 24 000 km² is shallower than 10 m. The marine waters of the Bay of Bengal are nutrient rich providing a suitable habitat for fish production. Marine fisheries consist of the industrial fishery using large trawlers and the artisanal fishery using mechanized and non-mechanized boats. The contribution of fisheries to the national economy of Bangladesh is substantial, particularly with reference to food consumption, nutrition, employment and export. The sector contributes 4.7% to the national GDP, 7% to the agricultural GDP and 10% to the export earnings. The average annual growth rate of the fisheries sector over the years is 4.6%. The fisheries sector provides full-time employment to 1.2 million professional fishermen and 11million part-time fisherfolk, the total of which is about 10% of the total population of the country.

The fisheries sector contributes about 78% of the animal protein intake in Bangladesh. However a continuous increase in fish production has not been able to cope with the fast-growing population. The country's fish production has increased from 640 000 metric tonnes (inland 545 000 metric tonnes, marine 95 000 metric tonnes) in 1975-76 to 1 373 000 metric tonnes (inland 1 079 000 metric tonnes, marine 294 000 metric tonnes) in 1996-97. But, at the same time, because of a fast increase in population the per capita fish consumption has declined from 33 to 20 g.

At present the marine fisheries sector contributes only about 22% of the country's total production, despite a sizeable marine and brackish water area within the EEZ. This sector has not been properly developed so far. Because of an unplanned and irrational increase in fishing effort many of the marine fish and shrimp stocks have already declined. As a result, coastal fishing has become non-remunerative and the fisherfolk are getting poorer, thus putting more and more damaging pressure on the resources.

2. DESCRIPTION OF THE MARINE AND COASTAL AREA

As already mentioned above Bangladesh has an Exclusive Economic Zone (EEZ) which extends to 200 nautical miles out to sea covering an area of 164 000 km². The territorial limit is 12 nautical miles out to sea from baseline (at 10 fathom depth counter). A large proportion of the shelf of Bangladesh is shallower than 10 m covering about 24 000 km² area. The whole shelf area of Bangladesh from 10 m depth to the shelf edge, i.e. up to 200 m depth contour, is about 43 440 km². The details of the marine water area are shown below:

AREA OF THE CONTINENTAL SHELF OF BANGLADESH

TOTAL MARINE AREA

WATER QUALITY PARAMETERS OF THE BAY OF BENGAL

Very little is known about the hydrological features of the water bodies of the Bay of Bengal in Bangladesh. The sea is changing and has a moving ecosystem with large varieties of bio-topics, regional geology, substrates, depths, currents and nutrients which differ from place to place. Generally, the inshore waters near the estuaries have very high turbidity due to heavy run-off from the major rivers. On the other hand the offshore waters are more transparent (The maximum Sechi Disc reading was 27 m).

The surface water temperature of the EEZ of the Bay of Bengal varies from 17o to 33oC and salinity from 18 to 37 ppt. The bottom water salinity ranges from 28 to 39 ppt. Waters of the continental shelf areas are relatively rich in plankton and contain high oxygen (4.8 ppm at the surface and 4.0 ppm at 35 depth), nitrates and minerals.

3. MARINE FISHERIES RESOURCES OF BANGLADESH

3.1 Exploited and un-exploited resources

Major fish species exploited

There are 475 species of fish and 36 species of marine shrimp in the marine waters. Among these, 90 species of fish are commercially important. The most common species of fish are as follows:

Major shrimp species exploited

The Bangladesh offshore commercial trawl fishery has been developed on the basis of the valuable exportable Penaeid shrimp resources. The commercial shrimp species are listed here:

Among the shrimp exploited Penaeus monodon is the most valuable and hence is the targeted species. But the highest contribution in the total production, however, is made up by Metapenaeus monoceros, brown shrimp which is about 63%. The major penaeid shrimp and demersal fish are abundantly distributed within the 100 m depth. So far four fishing grounds are identified within the continental shelf (Fig. 1). Distribution of shrimp and fish including other fauna at different depth with their percentages are shown in Tables 1 and 2.

Un-exploited and under-exploited species

Other than the fish species mentioned earlier a number of other important species of fish are available in the marine waters of Bangladesh which are either unexploited or exploited only as by-catch or as incidental catch by the existing trawl or gillnet fisheries. It is worth mentioning in particular the species listed below:

Tuna and Skipjack

Mackerels

The drift gillnetters also catch mackerel as by-catch of the hilsa fishery. Four types of mackerel (e.g. king mackerel, Spanish mackerel, Indian mackerel and short bodied mackerel) were recorded. These species are also found to occur in the trawl catch accidentally:

The others include 4 species of sardines, 3 species of anchovies, 13 species of carangids and 5 species of lobsters which are caught by gillnets, shrimp and bottom fish trawlers, as by-catch.

Non-conventional resources

Some cephalopods are also caught by the bottom fish and shrimp trawlers as by-catch. These are also found in some artisanal fishing gear at their younger stages. Three species of cephalopods (Sepia offininalis,Loligo spp., Octopus sp.) were recorded.

Sharks and rays are exploited by drift gillnets as well as by longlining. The y2859e species recorded were Sphyrna blochii, Stegostoma fasciatum, Chiloscyllium indicum, Scoliodon walbeehmii, S. sorrakowah, Carcharhinus menisorrah, Pristis cuspidatus, P. zijsron, Rhynchobatus djeddensis, Rhinobatos granulatus and Dasyatis uarnak.

3.2 Standing stock

A number of surveys have been conducted since 1958 in the marine waters of Bangladesh. Most of these surveys were exploratory in nature and oriented to studies for fisheries feasibility. Some surveys were conducted to assess the standing stock of the marine resources, particularly the demersal part of it. However, hardly any survey work has been done for a reasonable assessment for the pelagic resources.

Fig. 1 Fishing and Shrimping Grounds in the Continental shelf of Bangladesh

TABLE 1. DISTRIBUTION OF SHRIMP AND FISH INCLUDING OTHER AQUATIC FAUNA
WITH PERCENTAGE BY WEIGHT AT DIFFERENT DEPTHS OF THE BAY OF BENGAL

TABLE 2. DISTRIBUTION OF COMMERCIALLY IMPORTANT SPECIES OF FISHES
AT DIFFERENT DEPTH CONTOURS OF THE BAY OF BENGAL

The demersal fishery resource assessment results are found to vary (West, 1973). Through a desk study West estimated a standing stock of demersal fish of 264 000 to 374 000 metric tonnes and that of shrimp standing stock as 9 000 metric tonnes. His estimation was, however, criticized by many authors. The recent results, i.e. FRIDTJOF NANSEN and ANUSANDHANI surveys before and after 1984 bring out similar results. The standing stock of demersal fish was estimated within a range of 150 000-160 000 metric tonnes by these surveys. At the same time, the standing stock of shrimp was estimated between 2 000 and 4 000 metric tonnes by different authors (Penn, 1983 and White & Khan, 1985).

3.3 Maximum sustainable yield

The results of stock assessment studies have been used to find out the fisheries potential for different resources. At this stage it has been estimated that 40 000 to 55 000 metric tonnes of demersal finfish can be harvested annually from the offshore fishing grounds lying between 10 and 100 m depth zones. The maximum sustainable yield of shrimp has been estimated to be 7 000 to 8 000 metric tonnes annually which also includes resources of shallower water zones. (Khan, et al, 1989).

4. PRESENT EXPLOITATION PATTERNS

4.1 Industrial/Trawl Fishery

The commercial trawl fishery developed in Bangladesh from 1972. At the present there are 45 shrimp trawlers and 14 finfish trawlers in operation. The finfish trawlers also include six trawlers owned by the Bangladesh Fisheries Development Corporation (BFDC) a public sector body. The overall length of shrimp trawlers varies from 20.5 to 44.5 m and that of the finfish trawlers ranges from 28.0 to 30.5 m. The engine power varies from 350 to 1200 HP, but mostly falls within the range of 550-850 HP. The manpower employed in the fish and shrimp trawl fisheries consists in about 23 crew members on board commercial trawlers, 6-10 and 3-15 on board mechanized and non-mechanized boats respectively.

The finfish trawlers mostly carry out single trawling from the stern with high opening bottom trawl nets ith 60 mm mesh size at the codend. The shrimp trawlers use outriggers and operate two to four nets at a time. These trawlers used modern shrimp trawl nets with the codend having a mesh size of 45 mm. The headrope length of the shrimp trawl net ranges in the trawler fleetfrom 15 to 26 m. Almost all the vessels are equipped with modern navigation, communication and fish finding equipment. Though trawl fishing has been restricted to operate within the 40 m depth contour they are found operating even up to a depth of 10 m. The y2859e shrimp and fish species exploited by the trawl nets are Penaeus mondon, P. merguiensis, P. indicus, Metapenaeus monoceros, M. brevicornis, hartail, promfret, goat fish, cat fish, croakers, bombay duck, lizard fish, etc.

Fish landings by the commercial trawler fleets are within the range of 8 000-12 000 metric tonnes which is only 20% of the actual catch while 80%, equivalent to 35-45 000 metric tonnes (White and Khan, 1985) are discarded as low value by-catch at sea.

4.2 Artisanal/Small Scale Fisheries

Artisanal fishing operations in the estuaries and coastal waters used to be carried out by traditional craft until the mid 1960s. Two organizations, namely, the Bangladesh Fisheries Development Corporation (BFDC) and the Bangladesh Jatio Matshyajibi Samabay Samity (BJMSS) started the process of mechanization of fishing boats by importing and introducing marine engines.

These fisheries include different types of fishing gear and craft. Some of the gear are operated by the mechanized/motorized boats and some boats with oars or sails, popularly known as row or sail boats. Some gear are operated without any boat. There are five different types of gillnet (i.e. drift gillnet, fixed gillnet, large mesh gillnet, bottom set gillnet and mullet gillnet), two types of set bagnet (estuarine set bagnet and marine set bagnet). Trammel net, bottom longlines, beach seine and many other nets which are scattered throughout the coast and estuaries. Area of operation of the y2859e fishing gear in the coastal and marine waters of Bangladesh is shown in Fig. 1.

The y2859e species exploited by these gear are Bombay duck, hairtail, croaker, cat fish, lizard fish, etc., and among the marine shrimp species, Penaeus monodon, P. indicus, P. merguiensis, Metapenaeus monoceros, M. brevicornis, Parapenaeopsis stylifera, P. sculptilis, etc. Out of the total marine catch (i.e. 294 000 metric tonnes) the artisanal fisheries alone contribute about 95%, of which 10% by the estuarine set bagnet, 19% by marine set bagnet, 1.5% by trammel net, 4% by bottom longline, 57% by gillnet and 3.5% by other gear.

According to the frame survey which was carried out by the Fisheries Resource Survey System (FRSS) of the Department of Fisheries (DOF) during 1984-85 a total of 17 331 non-mechanized and mechanized boats were found in operation in the marine artisanal fishery sector. Of these 3 317 were reported to be mechanized and 14 014 non-mechanized. According to a survey by the marine wing of the DOF, currently about 6 000 mechanized boats are now in operation of which 4 000 are registered with the Mercantile Marine Department (MMD). However, from another estimate (Nuruzzaman, 1991), the number of traditional and motorized boats in the estuaries and coastal waters of Bangladesh are 20 000 and 12 700 respectively.

The following nets are used in the marine and coastal waters which play an important role in contributing to catches:

i) Estuarine set bagnets (ESBN)

A set bagnet (or stow net) is a conical shaped net, which looks like a bottom trawl net but fixed at the bottom. The net is made up of four panels. The mesh size varies between 20 and 140 mm at the mouth and 5 and 22 mm at the codend. The length of the net varies from 8.5 to 41 m and the height of the mouth opening from 2 to 7 m. About 12 560 set bagnets were estimated to be in operation in the estuaries at depths ranging from 3 to 10 m (BOBP, 1993).

The nets are classified into four, according to size based on the measurements of the mouth opening, as shown below:

A total of about 185 species of finfish and shell fish were identified in the ESBN catches. These included 15 penaeid shrimp, 152 finfish and 18 other fauna. The major shrimp species like tiger shrimp (Penaeus monodon), white shrimp (P. indicus), brown shrimp (Metapenaeus monoceros, M. brevicornis, M. spinulatus), pink shrimp (Parapenaeus sculptilis, P. stylifera), etc., including some other fish species like Bombay duck (Harpadon nehereus), hairtail (Lepturacanthus savala), croaker/jewfish, promfret (Pampus argenteus), grunter (P. hasta), etc., were also caught by the net. The annual average catch rate (kg/haul) of shrimp, finfish and others were 1.50, 3.36 and 12.7 respectively (BOBP 1993).

The annual total production of all the species combined was estimated to be 75 312 metric tonnes from the ESBN fishery. The total production of penaeid shrimp from different coastal districts in the ESBN fishery was estimated to be 7 746 metric tonnes as shown below:

ii) Marine set bagnet (MSBN)

This net is similar to ESBN and the operational procedure is also similar to that of ESBN, but the mesh sizes of MSBN are normally a little bigger compared to ESBN. The length of this net varies from 10 to 40 m and the mesh size at the codend from 12 to 25 mm. This net is operated during the dry season at depths of 10 to 30 m from the island bases. The total number of MSBN found to operate was 3 852. The classification of MSBN according to size is shown below:

* Estuarine year round operation, ** Seasonal operation.

iii) Shrimp seed collection and by-catch (PN)

Fine-mesh push nets, fixed bagnets and dragnets are used along the coastline for harvesting post larvae of Penaeus monodon. The total number of fry collection gear were estimated as 198 770 in 1989-90. Eighty-three types of organisms were identified in the catch composition of the shrimp fry collection gear. Species composition in the by-catch of shrimp fry collection gear are shown in Table 3. The total annual catch of P. monodon fry is approximately 2 034 million. Total number of organisms (except tiger shrimp) caught by the shrimp seed collection gear were estimated to be almost 200 000 million in 1989-90 which were discarded on the bank. According to a survey conducted by DOF/BOBP during November 1989 to October 1990 in the four coastal districts about 300 000 people, including women and children, were involved in the collection of shrimp seeds.

iv) Beach seine (BS)

The beach seine is an encircling net operated from the beach in the shallow water. It is used along the coast, y2859ely concentrated in the Teknaf - Cox's Bazar area. The species caught in these nets are jewfish, anchovies, clupeids and small shrimp. There are about 558 beach seines operated in the coastal area of Bangladesh. The total production by the beach seine fishery in 1988-89 was estimated to be 8 080 metric tonnes. The average total catch rate (kg/day/net) for all species combined is estimated to 84 kg in the estuary and 213 kg along the coast.

v) Gillnets (GN)

Among the five types of gillnets, most are small mesh drift gillnets (SMD). The average mesh size of the gillnet (SMD) is 90 mm which is operated within 15-40 m depths. The principal catch of the net is Hilsa ilisha which contributed 49% to the total marine catch. This net also catches tuna, mackerel, sharks, etc., as by-catch. The annual average catch rate of all the species combined is estimated at 231 kg/day/boat.

The average mesh size of the large mesh drift gillnet (LMD) is 200 mm, which is operated within 15-40 m depths. The targeted species of this net is Indian salmon (Polynemus indicus). This net also catches grunter, shark, tuna, mackerel, etc., as by-catch. The annual average catch rate of all the species combined is estimated at 110 kg/day/boat.

vi) Trammel net (TN)

Trammel nets are three-folded type of gillnets targeting, when drifting on the bottom, penaeid shrimp but also catch valuable finfish species. These nets have recently been introduced in the country and their operation is concentrated along the Cox's Bazar-Teknaf coast. The mesh size at the inner wall of the net is 40-45 mm and made of nylon twine. This gear is operated by row boats within the depth range of 5-15 m. Major species caught by this net are white, tiger and brown shrimp, croakers, Bombay duck, catfish, etc. Adult fish are caught and this net is therefore considered to be harmless to the resource.

vii) Bottom longlines (BLL)

Bottom longlines are operated at the depth of 20-30 m, i.e. 20 km beyond the coastline, y2859ely from the Cox's Bazar base. These are operated by 6-16 HP mechanized boats. The targeted species are jewfish and croakers, but other species like salmon, catfish, threadfin bream, etc., are also caught. The species of fish caught by this gear are mostly at the adult stage and so the gear has no adverse affect on the resources.

viii) Other gear

There are several other fishing gear used in the estuaries of Bangladesh such as cast net, trap, harpoon, etc., for subsistence fishing and a few for part-time fishing by the fisherfolk living along the sea coast.

5. HISTORY OF THE TRAWL INDUSTRY IN BANGLADESH

Just after independence of the country the Bangladesh Fisheries Development Corporation (BFDC) initiated deep sea trawling commercially in 1972 with 10 trawler fleets received as a grant from the then Soviet Union. Different survey works revealed the satisfactory level of stocks of shrimp and fish in the EEZ of Bangladesh. Both local and foreign investors became interested in investing in fishing in the marine sector from the mid-1970s. During 1976-86, 114 trawlers were imported for local private ownership or joint ventures with Thailand including on the "Pay as you Earn" (PAYE) scheme against the 250 imported trawlers permitted by the Government. At that time the trawler fishery was declared as an "Open Industry" by the Government and a large number of trawlers were permitted to fish in the EEZ of Bangladesh. In that situation many unauthorized trawlers came to Bangladesh's territorial waters and started fishing. This resulted in heavy pressure on the marine fisheries resources. To face this negative situation and for the sake of conservation of marine resources the Government promulgated "The Marine Fisheries Ordinance"and "Marine Fisheries Rules"in 1983 and also some administrative orders (Appendixes IV-VIII). Upon implementation of the ordinance and rules the trawlers, which were engaged in illegal fishing, fled from the Bangladesh waters and the situation came under control. In 1985, the Government constituted a high power committee to investigate the total number of trawlers in operation, 73 trawlers were found at that time. On the basis of expert opinion, the committee recommended that the 73 trawlers be allowed to operated in the EEZ of Bangladesh. Since then no new trawlers have been permitted to fish. At present 68 trawlers are engaged in fishing of which 45 trawlers are shrimp and the rest are fish or mixed trawlers.

TABLE 3. Species composition in shrimp fry collecting gear;
Push net and fixed Bagnet (% of numbers)

6. PRODUCTION OF FISH FROM DIFFERENT SOURCES IN BANGLADESH

Production of fish from different sources during the years 1993-94 to 1996-97 are given below:

Species composition and percentage of total marine fish catch are shown below:

Annual total catch by different marine fisheries are shown in Table 4.

7. SHRIMP CATCH, BYCATCH, AND CATCH EFFORT DATA FROM SHRIMP TRAWLERS

The catch and effort data of the shrimp trawlers are regularly collected in a prescribed manner developed with the help of the UNDP/FAO project BGD/80/025 (Appendixes II and III). The trawl operators provide information according to the log sheets which are collected by the inspectors of the Marine Fisheries Office. This information allows to determine the catch per unit of effort. The table below shows the catch rate by the commercial trawlers during the years 1992-93 to 1998-99.

Among the commercial shrimp, important groups like the white and brown show a definite declining trend and the tiger, although not yet recovered to the 1992-93 level, showed signs of improvement during 1996-97, but declined again in 1997-98.

TABLE 4. Annual Total Catch of Marine Fisheries, 1996-97 and 1997-98

The percentage composition of different commercial shrimp for the last 6 years are given below:

8. ESTIMATION OF CATCH COMPOSITION AND CATCH RATES OF TRAWL FISHERY FOR THE YEAR 1998-90 AS CASE STUDY

There is no recent study which can be used to elaborate the catch composition, by-catch, production trends by the trawl fishery. Data from one study during 1991-92 and from trawl surveys in 1988-89 (by R.V. ANUSANDHANI and R.V. MACHHRANGA research vessels of the Department of Fisheries) were used to estimate catch and size compositions for the respective trawl nets: by fishing grounds, depth ranges and seasons covered by the commercial shrimp and finfish trawlers. Catch data from the commercial fleets up to 1990-91 were compiled for routine catch estimates and were used along with the detailed percentage of catch compositions from the survey data to estimate catch rate and production of individual species. The situation has changed considerably during the last few years as many of the fish or invertebrates like cuttlefish, squid, octopus, etc., became commercially important due to market expansion and there has been an increasing acceptability of marine fish. However, the study can still be used to understand the trawl fishery of Bangladesh. Percentage of catch composition of shrimp and fish including monthly and yearly catch data for the years 1992 to January 1999 are shown in Tables 5 and 6.

TABLE 5. Statement showing the percentage composition
of different species of shrimp by the commercial double rigger shrimp trawlers

· All shrimp are in Head-on
· Weight are in kg

Catch composition of shrimp trawl net

Eleven species of shrimp including spiny lobsters were found in the shrimp trawl catches, 15 species of commercially valuable finfish, 38 species classified as by-catch, 28 species classified as trash fish and about 8 small size other commercially important species which were usually discarded.

Major species of penaeid shrimp were brown shrimp, tiger shrimp, Indian white shrimp and banana shrimp. Noteworthy commercially high-valued finfish were tigertooth croaker, blotched croaker, Bombay duck, lizard fish, goat fish and ilisha shad. Pony fish, small size lizard fish, goat fish, croakers, tripod fish, puffer fish, squilla, swimming crab and small molluscs and flatfish were considered as trash fish. Cuttlefish, squid octopus, shark and ray are also discarded as by-catch.

The number of species or groups of species (No.) of the above mentioned categories with their percentage by weight caught by the shrimp trawl net at different depth ranges are shown below.

From the catch records a noticeable decline in the relative proportion of white shrimp and an increase in the proportion of brown and tiger shrimp were found in the 30-80 m depth ranges compared to those in the depth range below 30 m. Among the commercially valuable finfish species, an increase in the relative proportion of hairtail, mackerel and silver pomfret were evident in the depth range 30-80 m. Croaker continues to y2859etain a relatively high proportion both in the < 30 m and 30-80 m depth range. Among the by-catch species, threadfin bream and tongue soles were significantly more in the 30-80 m depth ranges compared to <30m depth. The proportion of trash fish was also found to increase in the catch. Ponyfish and silver bidders were conspicuous among the trash fish. Occurrence of catch of 'other'species discarded were more or less similar at different depth ranges.

Catch composition of fish trawl net

All species caught by the shrimp trawl in the 30-80 m depth ranges were also observed in the finfish trawl catches. Smaller penaeid shrimps (Metapenaeus spp. and Parapenaeopsis spp.) were caught at relatively higher proportions in <30 m depth. In the 30-80 m depth range, tiger and brown shrimp were relatively more abundant. Though most of the penaeid shrimp were also caught in the fish trawl, their percentage of catch were much less compared to that of shrimp trawl catches.

Among the commercial fish catches, croaker occurre occasionally, unlike in the shrimp trawl catches, but Indian salmon, grouper, grunter, pomfret and ribbonfish catches were relatively higher even in the shallow waters (<30 m). In the 30-80 m depth, ribbonfish formed a very significant portion in the catch. The by-catch category included species which also increased with the fishing depth: Indian mackerel and false trevally in the <30m depth and seabream in the 30-80 m depth were significant additions in the fish trawl catches.

The percentage of trash fish in the catch in depth less than 30 m was significantly higher than in greater depth. Approximate number of categories caught by trawl net at different depths and percentages are shown below:

Catch rates of shrimp by shrimp trawl net

In the shrimp grounds of <30 m depth, the annual mean catch rate was estimated to be 5.7 kg/hour and it was 7.5 kg/hour in the 30-80 m depth. The peak months for different varieties of shrimp at different depth are shown below:

Catch rates of fish by shrimp trawl net

The annual mean catch rates of different categories of fish in the shrimp trawl catches, peak months and y2859e contributors to the peak catches at different depths are summarized below:

Catch rates of shrimp by fish trawl net

Penaeid shrimp catches were extremely low in the finfish trawls operated in <30 m depth (0.7 kg/30 min) and >30 m depth (1.3 kg/hour). With such trawls there is no record of shrimp catch in most of the year

Catch rates of fish by fish trawl net

The mean annual catch rates for different categories of finfish by the trawlers and the peak months of the catch rates at different depths are summarized below:

The predominant finfish variations at different depth ranges are as follows:

Annual variation in the catch rate of the penaeid shrimp

The annual variation in the catch rate of the commercial categories of penaeid shrimp (tiger, white, brown and others) from the shrimp trawl catches was recorded for the period 1981-82 to 1990-91 and are shown in Fig. 2.

The annual catch rate for all the penaeid shrimp combined shows year to year fluctuations, but an increasing trend was observed in the years 1981-82 to 1990-91. Annual catch rate of tiger shrimp showed less fluctuations, but a declining trend was evident with an average of 4.5 kg/hour until 1984-85 and a catch of 3.7 kg/hour thereafter, approximately 17% decline between the years 1981-82 and 1990-91. The white shrimp and the banana shrimp showed a slight increase in the annual average catch rate until the mid 1980s (1.5 kg/hour), but exhibited an noticeable decline (0.7 kg/hour) in the later years, approximately 50%, decline between 1981-82 and 1990-91. The brown shrimp had the highest catch rate with wide annual fluctuations and significantly increasing trend from 1980 (13.5 kg/hour) to 1990-91 (31 kg/hour), approximately a 130% gain. The small mixed or other shrimps (other Metapenaeus spp and non-penaeids such as Solenocera spp.) had a peak catch during the year 1984-85, which declined significantly thereafter but rey2859eed higher than the catch rates recorded between 1981-82 and 1983-84. These changes also indicate a significant change in the catch composition of penaeid shrimp in the trawl catches as shown below. Brown shrimp has become more important in the overall penaeid shrimp catch.

Fig. 2 Annual variations in the catch rate (kg/hr) for the commercial penaeid shrimp during 1981-82

The shrimp catch by the standardized fishing efforts for the last decade are given below:

* Efforts reduced due to loss/damage of trawlers during the cyclone in April 1991

Production including discarded bycatch with percentage composition

Using the catch data of the commercially important shrimp and finfish caught by the shrimp trawlers during the year 1989-90, the annual catch of the commercial categories of shrimp and fish were estimated to be 56 226.8 metric tonnes. Of which 2 714.8 metric tonnes (4.82%) was penaeid shrimp, 70.9 metric tonnes (0.13%) lobster, 6 898 metric tonnes (12.27%) high-value finfish, 26 568 metric tonnes (47.25%) low value by-catch, 14 534.9 metric tonnes (25.86%) trash fish and 5 439.4 metric tonnes (9.67%) other species. Among the total catches, Penaeid shrimp, lobster and high value finfish species, amounting to about 18% are retained and the rest of the catch which is low value by-catch, trash fish and other species amounting to about 82% are discarded at sea.

Utilization of trash fish

At present about 5-7% by-catch (low value small fish and other discards) of the total catch are landed. Some of these (about 2%) are exported by a few private companies after some value addition. The rey2859eder is sold at the local markets.

9. ANALYSIS OF CATCH DATA INCLUDING BY-CATCH AND SIZE COMPOSITION OF CATCHES FROM THE SHRIMP TRAWLERS

Analysis of 1 hour haul

There is no detailed study and analysis for the catch of commercial shrimp trawls to indicate type and size composition of different species caught including by-catch. However to give an idea of what may occur in a commercial shrimp trawl, the detailed composition of the catch from one haul during a survey cruise (by the research vessel R.V. ANUSANDHANI) in the year 1997 is given in Table 7). The catch included two species of commercial shrimp, 1 species of lobster, 11 species of commercially valuable finfish including other shell fish. In addition to that 12 species of juveniles of commercially valuable fish and 15 species of adult small size fish were also caught and considered as trash. Two other fish species, T. potoca and trigger fish are also considered as true trash. Low value species and trashfish are generally discarded by the commercial shrimp trawlers (Table 8).

The catch which is analysed in reference also includes some macrobenthos species such as sponges, jelly fish, sand dollars, star fish, sea urchin, sea turtle, octopus, molluscs, sea anemone, sea cucumber, sea snake, sea weeds, coral, etc. These are commonly caught by the commercial fish and shrimp trawlers and are discarded as by-catch. The percentage composition and catch per unit of effort of these species were not studied in detail. Most of the above mentioned species, except the turtles and snakes, were somehow affected due to contact with the trawl net. The turtles and sea snakes can escape damage because of their strong exoskeleton and skin respectively.

10. IMPACT ON BIO-DIVERSITY AND ON ECOLOGICALLY SENSITIVE AREAS OF THE MARINE ECOSYSTEM

10.1 Impact of shrimp trawling on shrimp resources

Exploitation of marine shrimp resources in Bangladesh comprises y2859ely of five species of Penaeus, three species of Metapenaeus and two species of Parapenaeopsis genus. Among these, all of the genus, Penaeus in general and particularly P. monodon and P. indicus, are the most targeted species due to their higher market demand. Present shrimp trawling in marine waters is significantly concentrated for harvesting tiger shrimp (Penaeus monodon). Harvesting regimes of this species comprise three major stages, i.e. offshore trawling, inshore artisanal fishing and post-larval shrimp collection from the coastal waters. This multi-sectoral exploitation pressure, particularly on this species, has created a continuous declining trend over time which is shown in the table below. Depleted catches of this species is a sign that the stock may collapse in the near future.

It is noted that the offshore waters of Bangladesh possess the largest shrimping grounds among the South Asian nations but competition in commercial tiger shrimp trawling is definitively leading to a decreasing standing stock of shrimp.

Table below shows percentage of species composition of shrimp caught in the shrimp trawling:

Source: Marine Fisheries Department, Chittagong.

10.2 Impact of trawling on marine living aquatic resources

No extensive work has been done to evaluate the effects of shrimp trawling on other marine aquatic resources and habitat, but some observation during the past two decades has shown that shrimp trawling has a negative impact on the marine fisheries resources. The most extensive damage is the wastage of resources when discarding by-catches. Extensive catch without consideration of breeding seasons effects the breeding cycles of fish and shrimp. Habitat destruction of the benthic flora and fauna was also noticed, as the trickler chains of the shrimp trawl nets are continuously dragging on the bottom of the sea. These effects of trawling on the marine resources are described below in more detail:

i) Wastage of fisheries resources

It is estimated that 80% of the fish caught by shrimp trawlers is discarded at sea. The amount of by-catch discarded was estimated to be 35 000-40 000 metric tonnes. This wastage is alarming in a country like Bangladesh where there is a serious scarcity of fish to meet the national demand. Reasons for by-catch discards are identified as follows:

Technical:

- Limited chilling or cold storage capacity, especially in smaller trawlers.
- Possibility of heat shock damage to high value shrimp by retention of large volumes of fish, and
- Difficulties related to transfer to other vessels at sea.

Financial:

- Low price of landed by-catch vis a vis shrimp;
- Lack of market development for value added product options, and
- Lack of marketing infrastructure

Institutional:

- Trawler owners are entirely motivated by high returns from shrimp and are not interested in landing by-catch.

There is a lack of policy regarding the discard issue and a systematic observation and research programme on the subject should be initiated.

The major reason for discarding is size rather than species. Discards of under-sized fish of commercial fish species have a particularly negative impact on the resources. There is no system in Bangladesh to assess the discard amounts.

Non-commercial, non-edible, species have obviously little access to markets and are therefore wasted most of the time.

Years of experience from similar fisheries around the world has clearly demonstrated that the production of certain fish products, such as frozen minces are not perceived as fish by the prospective consumer.

When the net is hauled and the catch spills on the deck, it is immediately sorted by the crews with priorities in mind. Recovery of the shrimp is the first consideration; second is the selection of large high value fish. During every part of the voyage, it is most likely that all other components of the catch will be thrown back to sea. This includes genuine trash, which cannot be utilized (for example seaweed, molluscs, non-penaeid crustaceans and small inedible fishes) and also smaller (but often larger than 15 cm) low value species of fish, like croakers (Sciaenbidae), cat fish and jack fish (Carangidae). Only toward the end of a voyage, when the available storage space is easier to predict, attempts are made to retain the miscellaneous by-catch. The BOBP and NRI studies on shrimp by-catch during 1990-91 indicated that no solution has been found to utilize the by-catch.

ii) Detrimental effect of shrimp trawling on the resources

There are no currently published analysed data which prove that shrimp trawling in the Bay of Bengal has had a significant detrimental effect on the demersal finfish fishery. However, the composition of the catches is not exclusively small species but also many fish at first maturity. It follows that apart from the sheer waste of a protein resource, there exists the unproved possibility that the shrimp industry is adversely affecting stocks of finfish which could be harvested by other fishermen. The abundance and diversity of coastal fishery resources have supported vibrant small scale fisheries for centuries. A feature of these coastal fishery resources is that many species increase in size with depth. This highlights the significance of the near shore as nursery grounds for many shrimp and finfish and concentrated small and large scale fishing on these areas causes serious damage to the resources at the nursery stage. The abundance of many valuable shrimp in near-shore waters and the concentration of finfish in areas of less than 40 m depth has encouraged the incursion of trawlers on shallow grounds. Fishing in these shallow nursery areas has resulted in many juveniles being killed before they get the chance to mature and add substantially to production. The gear used by the small-scale fishery has no adverse effect on the bottom of the near shore areas, but there is serious damage to the bottom communities by shrimp trawling in these areas.

iii) Reduction of recruitment due to killing of spawners

The trawler fleet at present has no restriction on fishing activities in respect of seasons. They harvest all sizes of fish and shrimp, some of which could spawn if not caught, thereby hampering recruitment. The existing rules for the closed season to facilitate the breeding of shrimp and other species are not in force. The result is indiscriminate trawling throughout almost the whole year leading to depletion of the spawners.

iv) Effect on benthic communities

The shrimp trawlers are fishing with two to four trawl nets at a time. In this kind of trawling, heavy chains called trickler chains are attached to the bottom line of the mouth of the trawl net which is dragged over the sea bed to drive shrimp into the trawl nets, destroying other shellfish, worms, sea urchins and all other bottom dwelling creatures. The whole benthic habitat including nests of many benthic organisms are being destroyed by trawling activities. The whole shrimping ground of Bangladesh is criss-crossed by the shrimp trawlers. In comparison to a field being ploughed over and over again, the intensive dragging of trawls kills and prevents the benthic organisms to settle.

There are no extensive sea grass beds in the Bangladesh marine waters except a few patches of seaweed and some reefs which are also being destroyed by shrimp trawling.

The benthic organisms are supposedly the most essential part in the food chain of the oceanographic environment. From the estimate made so far on the destruction of benthic fauna and their habitats by the shrimp trawling activities, the situation is alarming. There is a continuous destruction of the benthic habitats and organisms by the shrimp trawl nets which will lead on shrimp fishing grounds to the extinction of most of the benthic fauna and ultimately break the food chain seriously affecting the marine ecosystem.

Trawling profoundly disturbs the sea bed, churns and resuspends sediments. A shrimp trawler with 4 nets, 15 m in width towing 5.55 km per hour (3 knots) scrapes about 1 km² of seabed in 3 hours. Trawling affects benthic communities both directly and indirectly. Direct effects include damage (and often death) of target and non-target species due to contact with the trawl nets and physical alteration of the seabed. Indirect effects include the resuspension of sediment particles, toxic chemicals, and nutrients, as well as discarding of by-catch, which affects food chains.

The sea floor is not covered by homogeneous, featureless, accumulations of sediments, but is sandy and muddy with a complex structure made up from non-living objects (rocks, shells, worm-tubes, etc.), living organisms (seaweeds, sponges, bryozoans, molluscs) and most of all, the results of biological activities such as burrowing.

Bottom trawling affects the benthos when churned-up sediments resettle. Suspended particles in the water increase an average of 1 000% shortly after trawling. In addition to burying benthic organisms, resuspended sediments can diminish photosynthesis in the water column inhibiting feeding and raising the metabolic rate of clearing sediment particles in suspension-feeding organisms. As a result, frequent resuspension can change the dominant species in the benthic community from suspension feeders to deposit-feeders (WRI, et al, 1922).

Extent of damage on the benthic communities by the shrimp trawl net

In Bangladesh at present there are 45 shrimp trawlers ranging in length from 20.5 to 44.5 m in operation. Out of the 45 trawlers, 32 use 2 trawl nets and 13 use 4 trawl nets during fishing operations. For trawlers using 2 nets the mouth opening of each net during operation ranges from 21 to 26 m (average 23.5) and for trawlers using 4 nets, the mouth opening of each net varies from 13 to 15 m (average 14 m). The surface of the sea bottom affected by the shrimp trawl nets is shown in Fig. 3.

Each of the shrimp trawlers using two nets operate 160-176 days (average (168) per year and 20-22 days (average 21) per month. Duration of each haul ranges from 3-3.5 hours (average 3.25). The four net users operate 220-250 days (average 235) per year and 22 to 25 days (average 23.5) per month. Duration of each haul ranges from 4 to 5 hours (average 4.5). Trawlers with two trawl nets operate 4.92 hauls per day, i.e. (168 x 4.92) = 826.56 hauls per year and (3.25 x 826.56) = 2 686.32 hours per year. Trawlers with four trawl nets operate 3.55 hauls per day, i.e. (235 x 3.55) = 834.25 hauls per year, i.e. (834.25 x 4.5 hours) = 3 754.13 hours per year.

To calculate the sea bottom affected by shrimp trawling the following methods were used:

Area covered per hour = width x speed of the trawler

(Trawler using 2 trawl nets):

Speed 3 nautical miles (5.55 km)
Head rope length or width of one trawl net = 23.5 m
Total width of 2 nets = 23.5 x 2 = 47 m           47    =  0.047 km
                                                                   ——
                                                                   1000
Therefore, the area covered per hour per trawler = 0.047 km x 5.55 km = 0.26 km

Area used for one haul per trawler using 2 nets = 3.25 hours x 0.26 km² = 0.845 km²

Each trawler operates 4.92 hauls per day

in 168 days (per year) = (4.92 x 168) = 826.56 haul/trawler/year

Therefore 32 trawlers operate (32 x 826.56) = 26 449.92 hauls/year

A. Bottom area covered in one year by 32 shrimp trawlers operating two trawl nets at the same time:

26 449.92 hauls x 0.845 km² = 22 350.18 km²

(Trawlers using 4 trawl nets):

Speed 3 nautical miles (5.55 km)

Head rope length or width of one trawl net = 14 m

Total width of 4 nets =14 m x 4 = 56 m          56    =  0.056 km
                                                                   ——
                                                                   1000
Therefore area covered per hour per trawler = 0.056 km x 5.55 km = 0.31 km²

Area used for one haul per trawler using 4 nets = 4.5 hours x 0.31 km² = 1.40 km²

Each trawler operates 3.55 hauls per day

In 235 days (per year) = (3.55 x 235) = 834.25 hauls/trawler/year

Therefore 13 trawlers operate (13 x 834.25) = 10 845.25 hauls/year

B. Bottom area covered in one year by 13 shrimp trawlers operating four trawlnets at the same time :

10 845.25 hauls x 1.40 km² = 15 183.35 km²

Total area covered by the nets of (32 + 13) = 45 shrimp trawlers in the continental shelf of Bangladesh is (22 350.18 km² + 15 183.35 km²) = 37 533.53 km².

From the above estimate it is seen that 45 shrimp trawlers operating in the marine waters of Bangladesh damage severely the benthic communities and the habitats of the benthos covering an area of about 37 533 km² at least (almost a quarter of the total EEZ) for 168 to 235 days in the year.

v) Changes in species composition

The increased intensity of exploitation of resources by trawling has induced achange in prey-predator relationships. Consequently, changes in catch composition have been observed. The high value demersal fish like red snappers, groupers and large croakers are declining. There is an increase in low value threadfin breams, red fish and small catfish and jewfish. The large demersal finfish have declined partly because these species are long living, implying slow replenishment, and partly because shrimp trawlers are catching large quantities of juveniles. Due to decline in some of the large predators of cuttle fish and squid egges being ignored by the trawl fishermen, a significant increase of these high export value species was observed in the catch.

Fig.3 Surface of the sea bottom affected by shrimp trawl nets.

In general, the decline in the finfish and shrimp trawl catch rates has driven the trawlers towards the shallow water zones.

As an example, the change in the percentage composition was found evident by comparing the catch from a fish trawler ("F.V. MITALI") in 1991 and 1998 as given below:

vi) Depletion of resources

The rapid expansion of shrimp trawling has resulted in catches with large quantities of small fish and juveniles of finfish which are regularly discarded each year. At the same time, introduction of large vessels with high efficiency for shrimp trawling has resulted in excessive fishing effort in the depths of 20-70 m, which has made the penaeid shrimp stocks as well as other finfish vulnerable to overfishing.

It is in general agreed that the Bay of Bengal requires significant reduction in fishing effort.

10.3 Impact of trawling on environment

The quality of the sea water from the chemical point of view and biological productivity are affectedby the degree of discards from the trawl net and different discharges from the trawlers. Almost all the trawlers discharge the shipborne pollutants directly into the sea. Besides, about 35 000 metric tonnes of trash fish are discarded directly from the trawlers. In a relatively small fishing area, this sort of discard poses a serious environmental hazard by:

- polluting the environment;
- increasing animals of prey (shark) in the fishing ground
- decreasing dissolve oxygen
- increasing BOD (Bio-chemical oxygen demand)
- increase of pathogens
- incremental situation of disease outbreak, etc.

10.4 Interaction on other fisheries due to by-catch discards

The shrimp trawl fishery discards the juveniles of commercially important fish and shellfish which results in growth overfishing. This prevents the maturing of juveniles of important fish and shellfish. In addition, this fishery hinders the recruitment of sciaenids to the bottom longling (BLL) fishery due to catching the juveniles and pre-adults of this group. The shrimp trawl fishery also discards the small adult fish and other true trash which pollute the water when it is decomposed and hence affects the fishing ground. The dead fish attracts sharks which chase the other fish and disturb the fishing ground. Hence trawl fisheries are deprived of catching sufficient quantities of fish and shrimp. If the small adult fish were not caught and discarded by the shrimp trawlers these could also be exploited by the small-scale fisherfolk.

10.5 Impact of artisanal fishing activities on living aquatic resources

Artisanal fisheries include a number of different types of fishing gear and craft as described before. According to the recent survey reports about 55% of the artisanal production is contributed by the drift gillnetters (y2859ely composed of hilsa) and 30% is contributed by the estuarine set bagnet (most of the catches being juveniles and post juveniles of marine fauna). Catch records for some of the fishing gear used for artisanal fishing are described below:

i) Estuarine set bagnet fishery (ESBN)

The penaeid shrimp are mostly caught by this gear within the size of 2-15 cm except P. monodon which rangesfrom 5 to 20 cm showing peak at the size of 8 cm. The predominant length of brown shrimp (M. monoceros) was 5-7 cm but some were smaller. Most of the species caught are juvenile or at the immature stage. It is mentioned here that tiger, white and brown shrimp are considered to be mature at the sizes of 18 cm, 12 cm and 10 cm respectively. The size range of most of the finfish which were caught below 20 cm having the predominant size ranging from 5 to 10 cm indicating that the gear ESBN was y2859ely catching juveniles.

From a year round study (BOBP 1993) it was found that most of the marine shrimp and fish species, such as P. monodon, P. indicus, M. monoceros, M. brevicornis, M. spinulatus, P. sculptilis, H. nehereus, L. savala, S. domina, are overfished. This may have been influenced by the predominant catch of very small sizes of marine fauna by ESBN on the other hand very poor catch of the large sizes. But the estuarine species such as Acetes indicus and Setipinna taty are underfished, although some of the estuarine (non-marine) species are either over-exploited or fished at the optimum level, Palaemon styliferus, M. rosenbergii, S. sihama, S. tri, E. tetradactylum and P. paradiseus. The estuarine set bagnets are therefore considered to be destructive since it catches juveniles of a large variety of shrimp and finfish species of commercial value.

ii) Marine set bagnet (MSBN)

The species caught by this net is similar to that of the catches of ESBN excepting the catch at the pre-adult and adult stages. There is not sufficient indication of overfishing with the use of marine set bagnets.

iii) Beach seine (BS)

The beach seine also catches the juveniles of jewfish, anchovies, clupeids and small shrimp. It was observed from a year-round study (BOBP 1993) that most of the fish and shrimp species usually caught by this net are juveniles or fish at immature stages. During fishing large size turtle are also caught and left dead on the beach. By this gear a large number of non-conventional animals are also caught and discarded. This gear is considered destructive for the resources.

iv) Shrimp post larvae fishery (PN)

The coastal aquaculture industry in Bangladesh for culture of penaeid shrimp has developed and is mostly dependent on the supply of wild seed. Harvesting of tiger shrimp along with the larvae and post larvae of almost all fish, other shrimp including catch of the early stages of other marine fauna, are increasing day by day. According to the recent survey report (BOBP 1993) more than two billion larvae of Penaeus monodon are caught by the seed collectors annually along the coastline. Exploitation of penaeid shrimp by different gear at different stages of the life cycle is shown in Fig. 4.

This two billion tiger shrimp larvae is only less than two percent of the total catch of the seed collected, the rest of which (more than 98%, i.e. other penaeid shrimp 11%, caridean prawn 13%, finfish larvae 12%, zooplankton including other organisms 62%) is just discarded dead which includes larvae of other shrimp, fish and zooplankton.

On the other hand out of the total number of P. monodon removed from the sea and estuary by different fisheries, the shrimp seed fishery alone takes 99.568%, while the ESBN and trawl fishery take 0.215% and 0.215% respectively. But when the percentage of harvest is calculated in terms of weight the impact is just the reverse, i.e. the trawl fishery takes 61.27% and the shrimp seed fishery takes only 3.08% while ESBN 35.65%.

Fig. 4 Exploration of Penaeid Shrimp by Different Gears at Different Stages of Life Cycle

A considerable part of the two billion larvae of tiger shrimp (and also other fish and shrimp larvae) would have the chance to go back to sea to grow to adult size to make a substantial increase in the catch and catch rate of shrimp and fish by the offshore fishing gear, if not caught in the estuaries and along the coastline.

v) Gillnet fishery (GN)

The various species caught by drift gillnets (small and large mesh) are at the adult stages. There is therefore no damageto the resource. There is no evidence of damage from fixed gillnet, bottom set gillnet and mullet gillnet. However, fishing on hilsa spawner and jatka (juveniles of hilsa) in the riverine ecosystem affects the hilsa population of marine waters.

10.6 Impact of trawling on the national economy

Although the offshore trawling industry contributes to the national economy through export earnings, employment opportunities and industrial development, it sometimes also has an indirect detrimental effect on the economy by causing over-exploitation and environmental degradation. Over capitalization within the fishing industry leads to less return of revenues and the decrease of profits generates conflicts between fishermen competing for limited resources. In Bangladesh it is common for the offshore trawlers to exploit fishing areas of artisanal fisheries when there is a shortage of fish in their designated depths. This always creates social conflict between the trawlers and the artisanal fishermen.

It is evident that if the fishing industry continues to expand at the present rate more and more coastal fisherfolk will be driven to poverty level due to a loss of livelihood.

11. EXISTING RULES AND REGULATIONS FOR MANAGEMENT OF MARINE FISHERIES RESOURCES

The Government of Bangladesh promulgated the Marine Fisheries Ordinance for the management and conservation of marine fisheries resources. Under the provision of the Ordinance the Government framed the Marine Fisheries Rules. The Ordinance and the Rules are the y2859e regulatory legal framework for the management of the marine fisheries resources of Bangladesh. For the management of the trawl fisheries the Government has limited the number of trawlers to 73 which are allowed to operate in the EEZ of Bangladesh. The number of shrimp trawlers has been limited based on the previous survey results. At present the Government has a proposal. based on advice from various experts, to reduce the number of the existing 45 shrimp trawlers which are to be replaced by fish trawlers. The reasons behind this is that it is already proved that the shrimp trawlers are responsible for the wastage of resources by discarding the by-catch and also for damaging the marine ecosystems. The present management measures under the Marine Fisheries Ordinance has a provision to protect the fisheries resources. Some of the important provisions in the Ordinance are as follows:

i) Limiting the fishing days

The shrimp trawlers are permitted to fish for 30 days and the catch for each trip must have a least 30% fish in the total catch. This measure was enforced in order to limit the discard of by-catch.

ii) Facilitating escape of by-catch and small size fish and shrimp

Mandatory 45 mm mesh size at the codend for the shrimp trawl nets is being enforced to facilitate the escape of small size fish, shrimp and the juveniles of larger fish. However, during the towing operation, the codend of nets are stretched and as such the mesh opening tends to become smaller restricting the escape of small fish. So the effectiveness of this system needs to be evaluated.

iii) Depth zone restriction of 40 m

There are provisions for restricting the shrimp and fish trawling within a 40 m depth zone. This measure at present is not in force due to a High Court injunction against it. This measure although initially designed to establish the rights of the artisanal fisherfolk is also to protect the nursery grounds of marine fish and shrimp including the smaller groups of fish and shrimp in the area. The survey results indicate that about half of the marine fish stock lives within the 40 m depth zone.

iv) Turtle excluder device (TED)

The use of the Turtle Excluder Device (Fig. 5) has been made mandatory to save turtles from being caught by the trawl nets. However, this order, again, is not in force due to a High Court injunction against it.

12. UTILIZATION AND EFFICIENCY OF TECHNICAL DEVICES BY THE TRAWL OPERATORS

Provision for the present management measures which were designed in order to reduce the amount of catch wasted by the shrimp trawl fisheries. The measures are to be implemented by the Marine Fisheries Office under the Department of Fisheries. The use of a prescribed mesh size is being ensured by random inspection of the trawlers before and after every fishing trip. Shrimp trawlers are not allowed to fish for more than 30 days and are encouraged to keep the bycatch on boardas far as possible. The mandatory provision of landing at least 30% fish of the total catch is also monitored. The Bangladesh Navy also takes part in regulating the trawlers activities.

The effectiveness of mesh size regulations in decreasing the amount of by-catch by the shrimp trawl nets in the tropical waters of the Bay of Bengal has not yet been studied. But from the assumption based on the studies in other parts of the world it was found that the mesh size regulation of the coded is not very effective in facilitating the escape of small or juvenile fish. Studies in this regard are essential to validate this assumption. Other measures such as the limitation of fishing to 30 days and the mandatory provision for landing certain quantities of fish, no doubt may help to bring some positive effects. These measures can be made more effective if, based on studies, the fishing days were further reduced. Preventing the shrimp trawlers from operating within the 40 m depth contour would help to bring down the quantity of by-catch discards as more than 50% of the fish stock, y2859ely the smaller groups of fish and shrimp, live within this depth zone.

The use of a Turtle Excluder Device (TED) to reduce catches of turtles is not popular with the trawler owners as they argue that it would also allow large size commercial fish to escape from the net. This is not totally unfounded as the design proposed for the TED has vertical bars, which would prevent the large size commercial fish from entering the codend. More studies on the effectiveness of BRDs and TEDs in reducing by-catch is necessary. The Government of Bangladesh made the use of the Turtle Excluder Device (TED) mandatory for shrimp trawlers to save the sea turtles. However, this is not in force as the trawler owners filed a petition in the High Court against it on the plea that this would result in catch reduction. The Court has put an injunction against this until further orders.

The by-catch reduction devices (BRD) used in other countries of the world have not been tested in Bangladesh yet. There are several designs of BRDs and experiments must be conducted to select the most effective ones for the tropical multi-species fisheries of the Bay of Bengal.

Modifying the codend of the net can facilitate the by-catch reduction. As the trawl net during the towing operation stretches longitudinally, the mesh opening in the codend tends to be smaller thereby reducing the escape of small fish. By using bridles or square shape mesh instead of diamond size mesh in the codend, the mesh rey2859es open thereby facilitating the escapement of small fish.

As far as the economic aspect of by-catch utilization is concerned, it has so far not been very profitable for the shrimp trawl owners to bring the by-catch back to land. In a country like Bangladesh where there are widespread food prejudices, with the majority of the people taking a negative approach to seafood, it is very difficult to market sea fish. However, the consumption of sea fish is increasing day by day due to short supply of fresh water fish in the markets and the trawler owners are landing more and more species of fish/bycatch. Shrimp is still the targeted species and when there is a better shrimp catch, the by-catch is usually discarded.

Fig. 5 Turtle Excluder Device (TED)

13. PERCEPTION OF SHRIMP TRAWLER OPERATORS ON ENVIRONMENTAL AND BY-CATCH ISSUES

The shrimp trawl operators are often very suspicious of the Government agencies and are of the opinion that the Government is imposing too many restrictions which are hampering their normal fishing operations. By this time several cases have been filed in the Court against some sections of the Marine Fisheries Ordinance. The restriction of shrimp trawling within 40 m depth zone, the closed season regime and the mandatory use of the turtle excluder device are under court injunctions. Communications with trawl operators and managers indicated that they do not perceive that shrimp trawling has a bad impact on the marine resources. The problem of low catches, according to them, is due to other destructive fisheries, such as shrimp seed collection and the estuarine set bag net fisheries which they feel are responsible for the destruction of the marine fisheries resources. They feel that the elimination of these harmful fisheries will help to increase bio-mass. There are also discussionsabout the quantity of by-catch which is discarded; the shrimp trawling operators claim that the known statistics regarding the quantities of by-catch discards are over-estimated. According to them the amount of discards has decreased in recent years as more and more fish species can now be marketed profitably: Non-conventional fish species are now being accepted by the people.

14. PERCEPTION OF THE OPERATORS OF THE TECHNOLOGICAL AND SOCIO-ECONOMIC CHANGES IN FISHING PRACTICES

The shrimp trawler operators seem to lack information about by-catch reduction devices (BRD) and many are of the opinion that introduction of any device would reduce their catch of shrimp and valuable commercial fish. The operators are not well aware of the use of square mesh and bridles at the codend to reduce by-catch. More effort is needed to inform the shrimp trawl owners and the operators on by-catch and its detrimental effect on the fisheries resources as well as on bio-diversity. The overall constraints preventing the widespread use of technologies designed to reduce by-catch in the shrimp trawl fisheries have to be further explored. Through limited communication with shrimp trawl owners and operators, it is clear that education and adviceon the use of by-catch reduction technologies are necessary.

15. TECHNICAL AND ECONOMICAL CONSTRAINTS FOR ADOPTION OF APPROPRIATE TRAWLING TECHNOLOGY

The trawler owners/operators are subject to various constraints. The constraints affecting perception and decision of the shrimp trawler owners/operators concerning the adoption of environmentally friendly techniques have not been fully analysed so far. The following assumptions have been made based on limited communication with industry people:

i) Lack of trust in Government agencies

The shrimp trawl owners seldom trusts Government initiatives regarding management of marine fisheries resources and sustainable fishing. They feel that the Government agencies are pressing them with regulations which have not been tested effectively in conserving the resources or are not based on scientific facts or arguments. The common perception is that, in many cases, the Government arbitrarily imposes restrictions which stem from the bureaucratic culture of keeping the private parties under strict control, the measures will not help conservation of resources and the scientific basis for the decision is weak.

ii) Ignorance about eco-friendly techniques

As already mentioned above the trawler owners/operators are, in general, not well aware of the different technologies being used worldwide to reduce the by-catch in shrimp trawling and there is often a firm belief that any devices being suggested will reduce the catch rate of shrimp and other commercial fish (while, in reality, there are devices which by reducing the by-catch prevent the target shrimp from being crushed by a large amount of it in the codend. When asked about the use of square mesh in the codend instead of diamond size mesh to keep the mesh open to facilitate the escape of small fish, the shrimp trawl operators seemed totally unaware of such an existing method. Similarly they were not even aware of the use of short selvage ropes along the codend. The design, effectiveness and potential benefit of using by-catch reduction devices (BRD) are not very clear to the fisheries management authorities and shrimp trawler owners/operators. No standard device for use in the tropical waters of the Bay of Bengal has so far been demonstrated or tested.

iii) Economic reasons

The various devices used to reduce by-catch in the trawl fishery are anyway perceived by the trawl operators as potentially reducing the catch of some fish species that are of good economic value. The trawl owners do not want to lose these catches as they supplement their incomes. If the shrimp catch declines the trawl operators will face the risk of losing profits. The underutilized fishhold space and the rise in price of the non-traditional species will encourage them to bring in more and more species and small sizes of different species which were discarded before. Awareness building to motivate the trawl operators towards the beneficial effect of conservation of resources is essential.

iv) Social reasons

Due to socio-religious reasons many species of marine origin are not eaten by the people of Bangladesh; while being treated as trash in the country, some of these species have a potentially very high value on the international markets.

16. ONGOING AND PLANNED RESEARCH AND STUDIES FOR PROPER MANAGEMENT OF MARINE FISHERIES RESOURCES

There has not been much research so far on shrimp fisheries in general and on shrimp trawling in particular. Valid scientific information in this regard is still lacking. No estimate of the type and amount of by-catch has ever been made so far. Likewise, there has not been any serious study on to what extent shrimp trawling is effecting the aquatic resources, bio-diversity and the ecologically sensitive environment. Research on different aspects of marine fisheries resources and also on resource utilization is needed. Only stock assessment programmes on a very limited scale havebeen madein the marine sector by the Department of Fisheries.

17. AVAILABILITY OF DATA AND INFORMATION, RESEARCH ACHIEVEMENTS AND NETWORKING CAPABILITIES

As already mentioned above, there is a lack of information. The data being collected from the commercial shrimp trawlers normally concern shrimp with commercial value only. There is nothing about other species of shrimp and fish including by-catch species. Information on the catches of shrimp from commercial shrimp trawlersare regularly reportedto assess the production of shrimp, trends of catch, etc. However, shrimp trawlers provide very little information on the fish catches which they land, although it is required by law that commercial trawlers keep detailed records of catch and provide the information to the Department of Fisheries. No attempt has ever been made to analyze and interpret the information collected so far to estimate the stocks of fish and shrimp. Very recently the cruise data for stock assessment performed by the Departmental research vessel in the EEZ of Bangladesh is being reported through a Regional Technical Assistance (RETA) project (ADB-RETA-5766) sponsored by ICLARM. Under the provision of the project the analyzed data will be disseminated through the internet to other countries associated with the project.

18. REQUIREMENT FOR STUDY AND RESEARCH AT THE NATIONAL AND REGIONAL LEVEL

There is definitely a serious need for more research on various aspects concerning shrimp fisheries, including fish/shrimp stocks, production trends, type and amount of by-catch, any detrimental effect on other fisheries, and , the socio-economical aspects.

From the review concerning the existing characteristics of shrimp harvest practices by different fisheries, it is clear that the present situation is very complex and shows a considerable threat to the coastal and marine aquatic living resources in terms of resource and conservation of bio-diversity. Moreover, the present fleet size of shrimp trawlers somehow depletes the standing stock while some over capitalization is leading to reduced economic benefits. It is very unfortunate that, until now, no precautionary approach or code of conduct has been applied to preserve coastal and marine habitats and the eco-system, to conserve the endangered species, to y2859etain generic and species bio-diversity of indigenous resources and to assess the potential impact of gear and fishery which are very essential for designing a proper fishery management system. In this context, the following research proposals are suggested aiming toward sustainable shrimp fishery management and policy through participation of all stakeholders, institutions, policy makers, fishery communities, etc., including also study of the impact of trawling on the benthic fauna, the potential damages in order to find out the measures to prevent it:

- to study different types of BRDs in shrimp and fish trawl nets,
- to study advantages and disadvantages of using diamond mesh in the codend of shrimp/fish trawl nets,
- to study the stock and MSY of the pelagic fishery resources in the Bay of Bengal and recommend an appropriate method of exploitation,
- to study the stock and MSY of other resources such as lobster, squid and cuttle fish and to find an appropriate method of their exploitation and utilization,
- to study the stock and MSY of shrimp resources,
- to study the proper utilization of by-catch,
- to study the benthic fauna as well as damage caused by shrimp trawling with protection measures,
- to study the conservation and propagation of seaweed,
- to establish data base management system through computer networking for the industrial and artisanal sectors should be established,
- to conduct socio-economic studies on trawler fishery, and
- to evaluate extension and motivation programmes which should be undertaken for the industrial as well as artisanal stakeholders.

19. CONCLUSION

The people of Bangladesh prefer to eat freshwater fish rather than marine fish and this explains why so far so much attention has been paid to the inland fisheries. However, with the increase in population, the demand for fish is increasing. At the same time the fish production from freshwater sources has declined for many reasons.

Marine fisheries are gradually becoming more popular with the people of Bangladesh. The coastal fisheries of Bangladesh are considered to be very important as about 95% of the total catch from marine sources comes from artisanal fisheries. The 5% catch comes from the commercial shrimp and fish trawlers from the off-shore waters. Total production of shrimp would be 118 734 metric tonnes of which the shrimp taken by commercial shrimp trawlers is only 3 508 metric tonnes (head on). However, these trawlers severely damage the marine fisheries resources. In addition, the pollution from discarding chemical products, y2859ely oil from the merchant navy may seriously affect fish populations and marine fauna, in general. In addition, it is estimated that there are about 1 252 industrial plants settled in the coastal region of Bangladesh (chemical, food, medicine industries, other). These industries have increased in number and their effluents going out to sea also affect the living resources and marine habitats.

At present there is no effective mechanism through which collection of information and monitoring of activities of both the artisanal and commercial fisheries sectors can be done. Implementation of all the provisions in the existing marine fisheries ordinance and rules at field level is very inadequate. Very few studies have been carried out so far on stock assessment of commercial marine shrimp and fish; there is a lack of information on different parameters of oceanography and socio-economics condition of the fishery sector. All these elements would be essential for proper management of the resources and their exploitation. Related studies and research are necessary.

The marine section of the Department of Fisheries in Bangladesh seriously lacks manpower and facilities (As already mentioned, since independence almost all efforts and inputs in the fishery were dedicated to the freshwater sector). Considering these limitations, exchange of information and experience and intensive cooperation among countries of the world are essential.

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