The Eastern Himalayan region has been identified as one of the 18 mega-biodiversity 'hotspot' areas of the world (Myers et al. 2000). Arunachal Pradesh constitutes 60.93% of the Eastern Himalayan region. Some documentation exists on the flora, but documentations on faunal aspects are still scanty, with scattered reports, mostly on birds and some large mammals. Although contributions to the fish fauna of the State have also been made, accounts of species compositions of many water bodies still remain undocumented awaiting explorations and studies of such aquatic systems. Descriptions of most faunal works have been added with special emphasis on fishes. The preliminary findings suggest 7 first reports for the district and 3 first reports for the State. Senkhi stream contributed 31.37% of the icthyofaunal families of the district and 29.52% of genera while the species representation was found to be 27.32%. The correlation matrix reveals an interesting fact that Dikrong and Pachin have more common species than Senkhi, which is a hill stream. The striking feature is the even distribution of species under family Badidae, Psilorhynchidae and Olyridae though their contribution of each lotic (Senkhi, Pachin and Dikrong) water body is merely a single species and hence these species will be most vulnerable once a mega dam comes in-between, restricting the migration of already threatened population.
