Status of Endemic Freshwater Ichthyofauna of Lower Subansiri River Under the Threats of Dam Construction and Anthropogenic Disturbances: An Assessment

Given its unique geographic location and diverse environment, lower Subansiri is a significant hotspot for freshwater ichthyofauna species. Unfortunately, the endemic fish diversity is now threatened by the construction of the large dams in addition to other increasing human anthropogenic activities. Thus, the goal of this chapter is to give the current status of ichthyofaunal diversity and assemblage pattern of Lower Subansiri during retreating monsoon and winter seasons. Investigation was conducted from October 2022 to February 2023. There are already 69 recognized species, spread over 16 families and 43 genera during our survey from 10 selected sampling sites. The collection contains true hill streams as well as semi-torrential fishes. Cyprinids were the most dominant family with 32 species and 17 genera, while Clupeidae, Engraulididae, Balitoridae, Nandidae, and Tetraodontidae represent one species of each. Ompok pabo, Badis badis, Channa gauchua, Systomus sarana, Cirrhinus reba, and Channa marulius were the most dominant species. The lowest Shannon Wiener diversity indices (H′ = 1.83) at the S1 sampling site suggest poor ecological health of the river. Overexploitation coupled with receding in water level due to construction of the dam was discovered to be risky that mostly affected the endemic fish diversity of Lower Subansiri River. The current study will aid in the planning, administration, and preservation of the Lower Subansiri River ecosystem and will also serve as a baseline for upcoming research.