Diversity and conservation status of freshwater fishes of the major rivers of northeast India

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. The region is criss-crossed by numerous rivers belonging to the three major drainage systems: the Barak–Brahmaputra, the Kaladan and the Chindwin. About 100 species of fish have been described from the region by workers from India, as well as from other countries. Fish survey tours have been organized in the past 30 years in the different river systems of the region. Our survey resulted in the description of more than 50 new species of fish. 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.