|Freshwater||246||59||No||260||55||Rahman, A.K.A., 1989|
|Conservation||Bangladesh faces a multitude of environmental problems, including limited access to potable water, various water-borne diseases, the overuse of commercial pesticides, intermittent water shortages, soil degradation, deforestation, and severe overpopulation. The country is experimenting with integrated pest control programs, such as the use of natural predators, and is a signatory of several international agreements related to, among other matters, ozone-layer protection, hazardous waste, and environmental modification. Though there is a list of freshwater fishes of Bangladesh, there is little information on the status of species within the country. The following information is to be sought: - Existence of conservation plans; - Current major threats to species; - Future potential threats to species; - Contact(s) for further information.|
|Geography and Climate||
The greater part of Bangladesh consists of alluvial plains and deltas of the Ganges and Brahmaputra Rivers and is less than 10 m above sea level. At it's eastern and south-eastern margin are the low-elevation Lusai and Garo Hills. The main tributaries of the Ganges are the Mathabanga, Ichamati, Bhairab, Kumar, Chitra, Nabaganga, Garai-Madhumati and Arial Khan. East of the Garai-Madhumati is an active area of the delta where rapid sedimentation is occurring. The Sunderbans in the extreme south form an area of mangrove forests and swamps that extend for about 165 km from east to west. The eastern hills rise to a maximum elevation of 600 m. The main rivers of this area are the Surma, Karnafuli, Halda, Kassalong, Sangu and Muhari. The northern part of Bangladesh is noted for its torrential streams, including the Mahananda, Korotoa, Jabuneswari, Teesta, Kangsha and Someswari. In the monsoon these streams carry large amounts of silt from the mountains to the plains below.
Bangladesh has a humid climate with warm summers and cool winters. The monsoon is the most important climatic factor. About 80 percent of the annual rainfall typically occurs during the summer monsoon period, which lasts from late May to mid-October. April is the hottest month, averaging about 28°C (about 82°F). The coldest month is January, with an average temperature of 18°C (64°F). Mean annual precipitation ranges from about 1,400 millimetres (about 55 inches) along the country’s east central border, to more than 5,080 millimetres (more than 200 inches) in the far northeast. Besides the normal monsoon-type rainfall, Bangladesh is subject to devastating cyclones in the months of April and May, and again from September to November.
Ref. Microsoft, 1996
Bangladesh has vast areas of freshwater. The inland water areas comprise the following:
rivers, canals, estuaries: 1,003,000 ha
natural depressions: 114,161 ha
ponds and tanks: 161,943 ha
ox-bows: 5,488 ha
Karnafauli Reservoir: 68,800 ha
flood plains: 2,800,000 ha
brackish water: 87,300 ha
Rivers, canals and estuaries
Rivers and canals cover roughly 5.8% of the total area of the country. Annual flooding of the rivers innundates about 70% of the total land surface. During the rainy season, rivers carry a heavy silt load. The southern portion of the Gangetic delta bordering the Bay of Bengal includes rivers with high tidal action and areas of mangroves. During high tide salt water enters freshwater rivers. In 1986-7 rivers and estuaries provided an estimated 195,117 tonnes of fish.
The minnows and carps (Family Cyprinidae) and catfishes from 11 families and 30 genera are the most important riverine species. Important commercial species include the major carps, the Ayre, the chital and the boal. The river shad is anadramous and forms the largest single species fishery in inland water. Hill streams in the north of the country are swift flowing and clear.
Bangladesh has a very extensive floodplain. The area is seasonally inundated by overspill from adjacent rivers, lakes and natural depressions. During the dry season there is an accumulation of animal dung, rotting vegetation and other materials. This material rapidly dissolves during early stages of flooding and results in an increase in productivity that provides essential conditions for reproduction, feeding and growth of many fish species. The floodplain produced 183,796 tonnes of fish in 1986-7.
Beels, Haors and Baors
'Beels' and 'haors' are natural depressions situated mainly in the northern half of the country with the largest concentration in old Sylhet and Mymensingh districts. The term 'haor' denotes depressions which are larger in size and resemble inland seas during the monsoon. The term 'beel' denotes natural depressions of smaller size. These areas produced an estimated 42,007 tonnes of fish in 1986-7.
'Baors' are also natural depressions usually formed by a change of course of rivers. Most baors are located in Jessore, Kushtia and Faridpur districts. Total estimated fish production from baors was estimated to be 1,174 tonnes in 1986-7.
Ponds, Tanks and Dighis
There are thought to be between 1.3 and 1.7 million ponds in Bangladesh, varying in size from 0.1 acres to about 75 acres. Estimated fish production from ponds was 142,876 tonnes in 1986-7, which is approximately 17% of the total fish production for the country. The main species in aquaculture are various native and introduced carp species. Ponds are frequently found in Comilla, Noakhali and Faridpur districts.
Many of the flood plains and also the hillstreams on the Bangladesh-Myanmar border are sites of exceptional biodiversity interest (Ref. 12217).
Ref. Rahman, A.K.A., 1989