Bay of Bangal Large Marine Ecosystem Bangladesh

Stock assesment

Marine fisheries surveys in the marine waters of Bangladesh dated back to 1857 and the latest survey is about 25 years old. Most surveys were exploratory in nature, looking at fisheries feasibility. Those surveys were undertaken to evaluate abundance (i.e. stock status) and promote marine fishery management in Bangladesh's water. Early surveys were mainly aimed at identifying good fishing grounds to prove that fishing was economical. The later surveys were aimed at predicting the standing stocks and how much of it could be exploited on a sustainable manner. Pelagic fish received little or no attention compared to demersal species, which have been viewed as potential targets for increased trawl fishery production.

Stock assessment in its simplest form involved measuring the abundance and distribution of fishery resources in an attempt to estimate the standing stock or biomass of the resource to provide a guide to what is potentially available for capture- often taken to be some arbitrary proportion of the estimated biomass. More comprehensive forms of stock assessment took into account the size, age and sex distribution of the target population, as well as its dietary, reproductive, migratory and other behavioral characteristics, the location of its feeding and spawning grounds, the current impacts of fishing activities and the effect of environmental variables. These variously allowed the determination of a stock's productive potential and its resilience in the face of exploitation, and permitted establishment of ways to maximize biological or economic productivity in a sustained manner.

Marine fisheries survey

The following marine fisheries surveys in the marine waters of Bangladesh were documented which dated back to 1857.
i . R. V. Novara (1857-1859: Oceanographic and functional in nature), Austria
ii. R. V. Valdivia (1898-1899: Oceanographic and functional in nature), Germany
iii. R. V. Investigator (1865-1902: Oceanographic and functional in nature), UK
iv. R. V. Golden Crown (1908-1909: 1st exploratory trawling), UK
v. R. V. Chosui Maru (1958-1959: 02 months Exploratory trawling), Japan
vi. R. V. Kagawa Maru (1960: 01 year exploratory trawling), Japan
vii. R. V. Kinki maru (1961-62: 02 year trawling in coastal regions), Japan
viii. R. V. Jalwa (1962-1970: 08 years marine biological and oceanographic studies), Pakistan
ix. R. V. Lesnoy (1969-1970: 02 months oceanographic study), USSR
x. R. V. Sagar Sandhani (1965-70: 03 years fisheries research), FAO/Pakistan
xi. R. V. Meen Sandhani (1965-70: 06 months fisheries research), FAO/Pakistan
xii. Lesnoy (November 1969-January 1970, USSR
xiii. R. V. Tamango (June-November 1972: 06 months fisheries research), USSR
xiv. B. N. S. Padma (1974: two trips on 21st and 28th March, 06 days, from Chittagong to St. Martin's Island, marine biological research), Marine Biology Deptt., Chittagong University, Bangladesh
xv. T. V. Kandari (1976: 03 days marine biological research), Marine Biology Deptt., Chittagong University, Bangladesh
xvi. Mitajava (1976-77: 01 year oceanographic research), Japan
xvii. Santamonica and Orion-8 (1976-77), Japan
xviii. R. V. Fisheries (1978-79: 10 days oceanographic research), Thailand
xix. Fishery Research Vessel-II (March 1979), Thailand
xx. R.V. Dr. Fridtjof Nansen (December 1979-May 1980), Norway (FAO/NORAD/BGD) through a joint FAO/ Norway fishery research programme, under which the Norwegian Fishery Research Vessel Dr. Fridtjof Nansen visited all BoB countries except India. The vessel made assessments of mainly demersal and small pelagic finfish resources, based primarily on echo-sounder surveys, fishing trials using pelagic and demersal trawls, and occasional sampling using other fishing gears such as bottom longlines and lobster traps.
xxi. B. N. S. R. Amin (1980: 03 days, 1st expedition of NCEERSO), Bangladesh
xxii. M. V. Hijbul Bahar (1980: 03 days, 2nd expedition of NCEERSO), Bangladesh
xxiii. R. V. Anushandhani (1981-84), Bangladesh (BGD 1983)
xxiv. FAO/BGD marine fisheries survey of 1984-86
xxv. Bangladesh Fisheries Resources Survey, demersal trawling with R.V. Machranga (1988-89), Bangladesh
xxvi. BIMSTEC (The Bay of Bengal Initiative for Multisectoral, Technical and Economic Cooperation) - SEAFDEC survey of the northern part of the Bay of Bengal (Myanmar, India, Bangladesh) during 25 October-21 December, 2007. Only the BIMSTEC survey of 2007 specifically describes the large pelagic species.

Fishing grounds

Following fishing grounds were identified through survey of Sagar Sandhani and Meen Sandhani (1968-71), FAO/Pakistan:
i. South patches, spans 3,400 km2 (towards around 15 km west of Cox's Bazar, 10-40 m depths)
ii. South of south patches spans 2,800 km2 (towards 5 km south west of Teknaf, 10-100 m depths). These two fishing grounds (south patches and south of south patches) lie between 20°50´N to 21°40´N latitude and 91°00´E to 91°50´E longitude
iii. Middle ground, 4,600 km2 (towards 30 km south of Hatiya and Patuakhali, 10-100 m depths). It lies between 20°50´N to 21°20´N latitude and 90°00´E to 91°00´E longitude.
iv. Swatch of no ground, 3,800 km2 (towards 29 km south of Dubla Island, 10-100 m depths). This area lies between 21°00´N to 21°25´N latitude and 89°00´E to 90°00´E longitude (Shahidullah 1983).
v Four different areas in the Middle ground and South patches have been declared as 'Fish sanctuaries' by the Government in the Bay of Bengal-Bangladesh maritime area.
Fishing grounds of the Bay of Bengal, Bangladesh

Stock status

As of 2011-12 a total of 166 industrial trawlers were harvesting only 7.61% (industrial fishery) and about 43,000 non- and mechanized boats (about 51% and 49% respectively) are harvesting 92.39% (artisanal fishery) of the total marine catch of 546,333 t (17.84% of total annual fish production). At present total annual fish production is 3.261 million tons of which inland catch is 26,83,162 t (82.26%) which mainly comes from substantial inland water resources that provide freshwater fish from aquaculture and capture fisheries. While marine catch is 5,78,620 t (17.74%). Historically industrial trawlers' cataches were within the range of only 6.3%-7.61% (mean 7%) of the total annual marine catch during 2000-01 up to 2010-11

The marine capture fisheries of Bangladesh consist of complex, multi-species resources. The stock surveys are of more than two decades old (of 1986-1989) and no recent stock assessment was done since then. FAO-BOBP/WP/36 of 1972-82 reported 380 species of which 215 species are demersal, 65 species are pelagic, 20 species of shrimps and 40 species of cartilaginous (elasmobranchs). Survey of Sagar Sandhani and Meen Sandhani (1968-71), FAO/Pakistan identified four fishing grounds in the BoB-Bangladesh jurisdiction. Surveys of Anushandhani (1981-84) and Bangladesh fishery resources survey, demersal trawling with R.V. Machranga (1988-89) was done to locate and know the exploitable demersal shrimp stocks. West (1973) reported 2,000-5,000 t of shrimp, 150,000-160,000 t of demersal fish and 60,000-120,000 t of pelagic fish stocks within the EEZ of Bangladesh and annual exploitable demersal shrimp stocks are around 7,000-8,000 t and fish stocks are around 40,000-50,000 t. Survey report of Penn (1982) has reveled demersal fish stocks of 264,000-373,000 t in the continental shelf area of Bangladesh of which allowable exploitation is around 175,000 t. It is still a mystery why pelagic stocks were not surveyed at that time.

Catch composition

Industrial trawlers: Trawler catches are recorded in nine sorted groups of which, cat fish, jew fish, Bombay duck, pomfret, shrimps and other fishes (unsorted) are the dominant ones. Comparative catch of 2005-06 and 2010-11 revealed that during these six years catch of cat fish decreased from 10% to 2%, catch of jew fish decreased from 10% to 3%, catch of shrimps decreased from 10% to 7% . While catch of Bombay duck and pomfret remained unchanged. Catch of unsorted other fishes increased from 68% to 86% during these six years. Statistics show total industrial catch gradually increased from 34,084 t in 2005-06 to 41,665 t in 2010-11, it seems that decreased percentages of cat fish, jewfish and shrimps during these six years are simply due to statistical changes of unsorted other fishes. When the total catches (t) of industrial trawlers were plotted year-wise against group-wise for these six years it confirmed the skewed impact of unsorted other fishes on the catch composition. Bulk harvesting of juveniles and immature fishes also reflect overfishing condition.

Mean trawler catch composition (%) in 2005-06 and 2010-11 periods in the marine waters of Bangladesh (Fisheries Statistical Year Book 2005-06 and 2010-11).

Mean trawler catch composition (t) during 2005-06 to 2010-11 periods in the marine waters of Bangladesh (Fisheries Statistical Year Book 2010-11).

Artisanal small-scale fishery is a complex multi-species and multi-gear scenario which include various kinds of gillnets, set-bag-nets (behundi nets), seine nets, push nets, long lines, trammel nets, etc (for detail see gear section). Similarly artisanal catches are recorded in nine sorted groups of hilsa, cat fish, Indian salmon, jew fish, bombay duck, pomfret, elasmobranchs, shrimps and other fishes (unsorted). Statistics show total artisanal catch gradually increased from 445,726 t in 2005-06 to 504,668 t in 2010-11, about 13.22% increment in these six years. During these six years catch percentages of hilsa remained roughly unchanged witting 41-44%, jew and cat fishes and shrimps remained unchanged within 7%, 3-4% and 10-11% respectively. Catch percentages of Bombay duck increased significantly from 7-8% to 11-12%, pomfret also increased significantly from 2.6% to around 8-10% and Indian salmon from 0.2% to 1%. While catch percentages of unsorted other fishes decreased from 23% to 13% and that of elasmobranchs from 1% to 0.8% during these six years. The result obviously reflects good condition of artisanal fishery but only overexploitation of sharks (elasmobranchs).

Mean catch composition (%) of artisanal fisheries during 2005-06 and 2010-11 periods in the marine waters of Bangladesh (Fisheries Statistical Year Book 2010-11).

Excerpt of various reports reveals the most abundant groups are croakers (Sciaenidae) 12.8%, catfishes (Ariidae) 11.6%, threadfin breams (Nemipteridae) 4.4%, jacks and scads (Carangidae) 3.2%, goatfishes (Mullidae) 3%, lizardfishes (Synodontidae) 2.9%, hairtail/ ribbonfishes (Trichiuridae) 2.5%, ponyfishes (Leiognathidae) 2.5%, grunters (Pomadasyidae) 2.1%, sardines and shads (Clupeidae) 1.9% and mackerels and tunas (Scombridae) 1.1%, etc. Commercially important fin-fishes are Jewfishes/croakers (Johnius sp., Otolithus sp.), Pomphrets (Pampus sp.), Mackerels (Scomberomorus sp., Rastrelliger sp.), tunas (Euthynnus affinis), catfish (Ariidae), scads, trevally (Carangidae), sardines (Clupeidae), anchovies (Engraulidae), sharks, skates and rays (elasmobranchs) and shrimps.

Fish species that are presently being exploited consists of mainly demersal fishes of shallow water and mid water. These include around 100 commercial species of which 15 species are highly commercial contributing around 75% of the total demersal harvest. About 20 important fish families in each depth stratum showed that 10 fish families contributed about 56-75% of the biomass in each depth stratum and 20 fish families contributed about 82-87%. The three most important families were Ariidae (catfishes) 11.99%, Sciaenidae (jewfishes) 1.37% and Nemipteridae (threadfin breams) 9.00%.
Important species of fin-fishes that contribute about 75% of the demersal catch in the marine water of Bangladesh

Scientific Name English/common name Local/Bangla name
Pampus argentius Silver pomfret Foli chanda
P. chinensis Chinese pomfret Rup chanda
Pomadasys hasta White grunter Datina
Lutjanus johni Red snapper Ranga koi
Polynemus indicus Indian salmon Lakkha
Lepturacanthus savala Ribbonfish/hair tail Churi
Arius spp. Cat fish Aeir/Kata mach
Johnius belangerii Croaker Rupali poa
Otolithoides argentius Croaker Poa
Namipterus japonicus Japanese threadfin bream Rupban
Upenus sulphurus Goat fish Sonali bata
Saurida tumbil Lizard fish Choukkha, Baro choukkha
Ilisha filigera Big eye ilisha Choukkha phasa
Sphyraena barracuda Great barracuda Darkuta
Muraenesox telabonoides Indian pike conger Kamila