Understanding fish assemblage structure using enviro assessment techniques in a Northwestern Himalayan reservoir of Beas River basin in Himachal Pradesh (H.P.), India.

Environmental factors play a fundamental role in shaping fish assemblage in aquatic ecosystems. The present study describes the fish assemblage structure on the spatial scale in Pong Reservoir, which lies in foothills of the Northwestern Himalaya within the river Beas basin. Through sophisticated enviro assessment techniques, using ArcGIS mapping, this study provides valuable insight into how physicochemical factors shape the fish assemblage in the reservoir. In total, 1211 individuals belonging to 8 orders, 10 families, 15 genera, and 19 species were recorded. The order Cypriniformes has the highest number of species. The invasive species Oreochromis niloticus was also documented for the first time in this reservoir. At a spatial scale, diversity indices reveal that the lacustrine zone had the lowest fish diversity. The transitional zone showed more species richness as compared to other riverine and lacustrine. The IUCN conservation status showed that among 19 fish species, two species (Wallago attu and Cyprinus carpio) are under vulnerable and only one species, Tor putitora, is under the endangered category. The majority of recorded water quality parameters fell within the acceptable range. CCA analysis of physiochemical parameters with fish abundance reveals that DO and turbidity were found to positively influence the species abundance. These findings provide a valuable resource for understanding ecology and also lay a solid foundation for the development of effective fisheries management strategies in this reservoir.