Bay of Bengal large marine ecosystem

Source: NOAA


caption Location of the Bay of Bengal Large Marine Ecosystem (Source: NOAA)

This Large Marine Ecosystem (LME) is characterized by its tropical climate. It is situated in the monsoon belt and receives high rainfall. Bangladesh, India, Indonesia, Malaysia, Maldives, Myanmar, Sri Lanka, and Thailand are the countries bordering the LME. Intensive fishing is the primary force driving the LME, with climate as the secondary driving force. The Global Environment Facility (GEF) is supporting a fisheries project, now in the preparation stage, to address critical threats to the coastal and marine environment, and to promote ecosystem-based management of coastal and marine resources. LME book chapters and articles pertaining to the Bay of Bengal LME include Dwivedi, 1993, and Aziz Ahmad et al, 1998.


For a description of the Bay of Bengal as a shared ecosystem, see Aziz Ahmad et al, 1998. The LME is affected by monsoons, storm surges, and cyclones but has no seasonal upwelling. However, in nearshore areas, the mixing of nutrient rich bottom waters and warm surface waters creates conditions similar to upwelling (see Dwivedi and Choubey, 1998). The number and intensity of cyclones in the northern part of the Bay of Bengal are likely to increase due to global warming. For more on the southwest monsoon, see Desai and Bhargava, 1998. Major rivers such as the Brahmaputra and Ganges discharge large quantities of fresh water into the Bay of Bengal (see Dwivedi and Choubey, 1998). For a map of freshwater drainage of the Northern Bay of Bengal, see Dwivedi, 1993, p. 45. This input of freshwater and silt impacts the salinity of the coastal and estuarine waters as well as coastal circulation patterns. It influences and governs LME dynamics during the southwest monsoon. For more information on hydrography and productivity, see Dwivedi, 1993. Wetlands, marshes, and mangroves play an important role in the overall productivity. The Bay of Bengal LME is considered a Class II, moderately productive (150-300 grams of carbon per square meter per year) ecosystem based on SeaWiFS global primary productivity estimates. Changing environmental conditions are influencing currents, productivity and coastal pollution. Lakes connected to the Bay of Bengal LME are changing. Some coastal areas serving as nursery grounds for commercially valuable species of prawns are polluted. For a map of distribution of zooplankton biomass in the Bay of Bengal LME, see Desai and Bhargava, 1998, p. 303. For more information on biological production and fishery potentials in India’s EEZ, see Desai and Bhargava, 1998. For benthic biomass production in the shelf region of the Bay of Bengal, see Parulekar et al, 1982. A graph is reproduced on page 303 of Desai and Bhargava, 1998. Six areas of critical biological diversity are: the Sundarbans, one of the world’s most extensive mangrove systems, Palk Bay, the Gulf of Mannar, the Marine (Wandur) National Park in the Andaman and Nicobar Islands, the Maldives Atolls, Mu Ko Similan National Park and Mu Ko Surin National Park in Thailand.

Fish and Fisheries

caption LME: Bay of Bengal (Source: NOAA)

The Food and Agriculture Organization (FAO) 10-year trend shows a steady increase in catch from 1.4 million tons in 1990 to 2.2 million tons in 1999 (see FAO, 2003). The average catch is 2 million tons. This tropical region has a relatively great marine biodiversity that is reflected in the catch composition. There is a high catch percentage for miscellaneous coastal fishes and pelagic fishes (tuna, yellowfin, big eye and skipjack). Herrings, sardines and anchovies represent more than 15% of the catch. The crustacean catch (shrimp is the major export earner) is just below 15% of the total catch (see FAO, 2003). Catch trends are quite diverse and it is difficult to identify a pattern due to the fact there is inadequate information on the status of the fisheries resources and their exploitation. For more information on the major fisheries in this LME, see Dwivedi, 1993. Despite a steady rise in total landings since the 1950s, there are signs that the harvest levels may not be sustainable, especially with regard to tuna fishing in the Maldives, Malaysia, Thailand’s Andaman coast and Sri Lanka. Ecological changes in the estuaries and coastal areas have not yet affected total production trends (see Dwivedi, 1993). The GEF-supported project is examining the issue of sustainable fisheries and food security. Heavy fishing through open access and the unauthorized incursions of foreign fleets is a comparatively recent phenomenon. There is an increase of competition and conflicts between artisanal and large-scale fisherman. There is an alarming increase in cyanide fishing in this LME’s coral reefs for the lucrative live food fish markets in Hong Kong and Singapore. Mangroves and estuaries--critical fish spawning and nursery areas-are also under stress or threatened by pollution, sedimentation, dams for flood control (as in Bangladesh), and intensive coastal aquaculture. In most of the countries surrounding the Bay of Bengal, clear policies, appropriate strategies and measures for the sustainable management of the fishery resources are weak. There is a need to establish a systematic data collection system in order to prepare a regional strategy. The University of British Columbia has detailed fish catch statistics for this LME. The FAO data can be seen in the graph "LME: Bay of Bengal," above.

Pollution and Ecosystem Health

caption (Source: NOAA)

The ecosystem stresses experienced are connected to the size of the coastal populations bordering the LME (see Aziz Ahmad et al, 1998). Issues of ecosystem health that are common throughout the region are: environmental stresses on the Bay of Bengal’s water quality; the degradation of many of the coral, mangrove, wetland and seagrass bed habitats that support fisheries; and the use of fishing gear that may affect the long-term sustainability of the fisheries resource. For more information on anthropogenic changes, see Dwivedi, 1993. The major rivers bring in large concentrations of pollutants from agricultural pesticides and industrial waste that damage fish spawning and nursery areas, cause fish kills and lead to possible changes in trophic structure. High levels of pesticides can be found along the coast, especially near cities and ports (see Dwivedi, 1993). A major part of Bangladesh consists of a delta plain positioned below the confluence of the Ganga, Brahmaputra and Meghna Rivers. Environmental refugees regularly flee the flooded plain, and many deaths occur with the floods. For a map of the effect of sea-level rise on low-lying Bangladesh, see Dwivedi, 1993, p. 51. Sediment loading in the Ganga-Brahmaputra watershed caused by accelerated soil erosion in the Himalayas is considered to be one of the main factors contributing to downstream flooding. In some regions of the Bay of Bengal, a change in composition of plankton species has been observed (see The Bay of Bengal Programme, 1994). There is heavy oil tanker traffic between Japan and the Middle East, with the main shipping route passing South of Sri Lanka before entering the Straits of Malacca via a passage below the Nicobar Islands. For this reason, oil spills are a major concern. In 1993, India approved a national oil spill contingency plan. There is inadequate information on pollution and sedimentation loads entering the Bay of Bengal, on coastal habitats and endangered species. This information is necessary in order to understand the functioning of the ecosystem and its reaction to stress over time.

Socio-economic Conditions

caption (Source: NOAA)

A quarter of the world's population resides in the countries bordering the Bay of Bengal Large Marine Ecosystem (see Aziz Ahmad et al, 1998). The high population depends on coastal resources for food and livelihood security. India will soon reach a population of 1 billion. It will require millions of tons of fish to meet minimum protein needs. This puts significant pressure on marine resources. There is an urgent need for long term planning for the conservation and management of the LME. Millions of tons of fish must come from aquaculture. Of the 400 million people living in the LME's catchment area, many subsist at or below the poverty level. For more information on artisanal fisheries, see Dwivedi, 1993. There are conflicts between large scale and small-scale fishermen. Poverty, unsustainable fishing practices and a decline in income from fisheries are contributing to a crisis. Addressing this crisis requires the coordinated effort of the 8 countries bordering the LME. Other economic activities in the LME are tourism (for instance in the Maldives), and the mining of coral and sand for construction. The Global Environment Facility is supporting a project to protect the Bay of Bengal’s marine environment. The initiative is mobilizing national and regional efforts to improve the food and livelihood security of the region’s coastal populations.


Bangladesh, India, Indonesia, Malaysia, Maldives, Myanmar, Sri Lanka, and Thailand are the countries bordering the LME. A Project Description for The Bay of Bengal Programme is available. For a map showing EEZs in the Bay of Bengal, see Desai and Bhargava, p. 298. There are numerous stakeholder groups involved in the fisheries of the Bay of Bengal (see Aziz Ahmad et al, 1998). For more information on policy frameworks in India, Sri Lanka, Indonesia, the Maldives and Malasia, and on the success of a community-based aquaculture enterprise in West Bengal, India, see Aziz Ahmad et al, 1998. A multitude of international, regional and sub-regional institutions operate in the Bay of Bengal, many of which have similar mandates, resulting in overlap and duplication. Fisheries organizations include the Indian Ocean Fisheries Commission (IOFC), the Indian Ocean Tuna Commission (IOTC), the International Forum for the Indian Ocean (IFIOR), the Indian Ocean Rim Initiative, the Asia-Pacific Fishery Commission (APFIC), and the Network of Aquaculture Centres for Asia (NACA). The Bay of Bengal Program (BOBP) is a regional fisheries project executed by FAO. It became operational in 1979 and involves all the countries bordering the Bay of Bengal with the exception of Myanmar. For more information on fisheries management and regulation, see the FAO web site. Other transboundary areas are oil spill planning, legal and institutional review, and pollution control measures. On the whole, the region lacks enforcement capabilities. Major organizations of the area include the Association of South East Asian Nations (ASEAN), the South Asian Association for Regional Co-operation (SAARC), the United Nations Economic and Social Commission for Asia and the Pacific (ESCAP), the South Asian Co-operative Environment Programme (SACEP), the UNEP Regional Co-ordinating Unit for East Asian Seas, and the Indian Ocean Marine Affairs Co-operation (IOMAC).


Articles and LME Volumes

  • Aziz Ahmad, H.B., Luqueman, A., Atapattu, A., Chullasorn, S., et al, 1998. Regional stewardship for sustainable marine resources management in the Bay of Bengal. In: K. Sherman, E. Okemwa and M. Ntiba (eds), “Large Marine Ecosystems of the Indian Ocan: Assessment, Sustainability, and Management.” Blackwell Science. ISBN: 0632043180.
  • Desai, B.N. and R.M.S. Bhargava, 1998. Biologic production and fishery potential of the Exclusive Economic Zone of India. In: K. Sherman, E. Okemwa and M. Ntiba (eds), “Large Marine Ecosystems of the Indian Ocan: Assessment, Sustainability, and Management.” Blackwell Science. ISBN: 0632043180.
  • Dwivedi, S.N. 1993. "Long-Term Variability in the Food Chains, Biomass Yield, and Ocenaography of the Bay of Bengal Ecosystem," in Kenneth Sherman, et al. (eds.), Large Marine Ecosystems: Stress, Mitigation, and Sustainability (Washington, D.C.: American Association for the Advancement of Science, 1993) pp. 43-52. ISBN: 087168506X.
  • Dwivedi, S.N and A.K. Choubey, 1998. Indian Ocean large marine ecosystems: need for national and regional framework for conservation and sustainable development. In: K. Sherman, E. Okemwa and M. Ntiba (eds), “Large Marine Ecosystems of the Indian Ocan: Assessment, Sustainability, and Management.” Blackwell Science. ISBN: 0632043180.
  • FAO, 2003. Trends in oceanic captures and clustering of large marine ecosystems—2 studies based on the FAO capture database. FAO fisheries technical paper 435. 71 pages.

Other References

  • Buku Tahunan Statistik Perikanan (Fishery Yearbook). DINAS PERIKANAN. Denpasar, Indonesia (various years).
  • Murty, V.S.N. et al. 1990. Report of the physical oceanographic characteristics of the Bay of Bengal during southwest monsoons. Technical Report. NIO/TR-8/90, National Institute of Oceanography, Goa, India.
  • Parulekar, AH, Harkantra SN, Ansari ZA., 1982. Benthic production and assessment of demersal fishery resources of the Indian Seas. Ind J Mar Sci 11:107-114.
  • Sastry, J.S., Rao, D.P., Murty, V.S.N., Sarma, Y.V.B. Suryanarayana, A. and Baby, M.T., 1985. Watermass structure in the Bay of Bengal. Mahasagar 18(2):153-162.
  • Sivasubramanian, K, 1985. Marine Fishery resources of the Bay of Bengal, BOBP/WP36 (RAS/91/051). Marine Fishery Resources Management, Sri Lanka. 66 pages.
  • Suryanarayana, A. 1988. Effect of wind and freshwater discharge on hydrography and circulation of the western Bay of Bengal. Ph.D. diss., Andhara University, Waltair, India. 91pp.

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the National Oceanic and Atmospheric Administration (NOAA). Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the National Oceanic and Atmospheric Administration (NOAA) should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.



(2008). Bay of Bengal large marine ecosystem. Retrieved from

1 Comment

To add a comment, please Log In.

Jack Grove wrote: 11-14-2010 12:16:39

In January 2010 I will be traveling across the Bay of Bengal from Singapore to SE India aboard ship. I will be lecturing on marine biodiversity, marine conservation and ocean currents. Periodically I will refer to this site and welcome any comments or questions. or