Envis Centre, Ministry of Environment & Forest, Govt. of India

Printed Date: Sunday, March 3, 2024

Northeast faces over-exploitation of freshwater biodiversity











Imphal: The freshwater fishes in India’s Northeast states are facing the threats from overexploitation, water pollution, flow modification, habitat loss, and exotic species invasion, as well as an additional factor, climate change, according to reports. 




Northeast India 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 Aquatic Ecosystem and Health & Management journal. 




“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 scientific report on ‘Diversity and conservation status of freshwater fishes of the major rivers of northeast India.’ “For instance, with the construction of the Ithai barrage in the Loktak lake of Manipur, there has been disruption in the migration of fish from the lake and some species have lost their spawning habitats.” 




Ithai barrage, a 35ft 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 768.9m 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 India preventing the natural breeding of Manipur’s state fish-Pengba((Osteobrama belangeri) at Loktak and its connecting major rivers as the fish comes from Myanmar’s Chindwin to upstream 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 the (Loktak) lake, Prof Vishwanath added. 




Northeast India has 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 the (NE) region is criss-crossed by numerous rivers belonging to the three major drainage systems: the Barak–Brahmaputra, the Kaladan and the Chindwin, the report said. 




About 100 species of fish have been described from the region by workers from India, as well as from other countries. 




As many as 40 species of fish are endemic to the Chindwin drainage and 22 to the Brahmaputra basin. The fish fauna of the Kaladan is poorly explored. Of the fish species in the Brahmaputra basin, 34% have not been evaluated for IUCN red list criteria, while in the Kaladan, 48.2% have not been evaluated, it added.










Source: Eastern Mirror