IMPHAL, Sept 27 - The freshwater fishes in Northeastern States are facing threats from overexploitation, water pollution, flow modification, habitat loss and invasion of exotic species, as well as climate change, according to reports.
North East has been regarded as the country�s future powerhouse. In 2001, the Central Electricity Authority while assessing the hydro-electrical potential of various river basins in the country, found the Brahmaputra basin to rank the highest with capacity for 168 projects and a power production potential of 63,328 MW, according to a scientific report in the journal, Aquatic Ecosystem and Health & Management.
�However, the construction of dams has been found to have a great impact on freshwater biodiversity,� opines Prof W Vishwanath of Manipur University�s Centre for Advanced Studies in Life Science in his report on �Diversity and conservation status of freshwater fishes of the major rivers of Northeast India�.�
�For instance, with the construction of Ithai barrage in Loktak Lake of Manipur, there has been disruption in the migration of fish from the lake and some species have lost their spawning habitats�, he said.
Ithai barrage, a 35 ft high dam and a major component of Loktak Multipurpose Project which was taken up in 1983 to provide regulated storage to generate 104 MW of power and lift irrigation, maintained the water level of Loktak lake at a constant level of 768.9 metre throughout the year.
As a result, it not only adversely affected huge agricultural as well as settlement area on the periphery of the lake, but it changed the entire hydrology of Loktak, the so called largest freshwater lake in NE preventing the natural breeding of Manipur�s State fish � Pengba (Osteobrama belangeri) at Loktak and its connecting major rivers as the fish comes upstream from Myanmar�s Chindwin through Manipur river.
Species such as Syncrossus berdmorei and Raiamas guttatus that were widely found in swamps, streams, and irrigation canals have been lost from these habitats around Loktak lake, Prof Vishwanath added.
North East has a rich freshwater fish diversity which is attributed to past geological history and the Himalayan orogeny which played an important role in the speciation and evolution of groups inhabiting mountain streams.
Stating that NE region is criss-crossed by numerous rivers belonging to the three major drainage systems: Barak-Brahmaputra, Kaladan and Chindwin, the report said. About 100 species of fish have been described from the region.
As many as 40 species of fish are endemic to Chindwin drainage and 22 to Brahmaputra basin. The fish fauna of Kaladan is poorly explored. Of the fish species in the Brahmaputra basin, 34 per cent have not been evaluated for IUCN red list criteria, while in Kaladan, 48.2 per cent have not been evaluated, it added.