Fish assemblage structure and habitat use of the snow fed stream Assiganga - a major tributary of river Bhagirathi in Central Himalaya (India)

Assiganga stream is an important tributary of Bhagirathi River in central Himalaya (India). The stream is characterized by heterogeneity in habitat and substratum features harboring diverse fish fauna. At present this stream is facing threat of being fragmented by the construction of two hydro-electric projects. Present study aimed to study fish diversity and their habitat use in Assiganga stream. This study reports fifteen species (14 indigenous and 1 exotic) belonging to 8 genera, 4 families and 3 orders. Snow trout, Schizothorax richardsonii (Cyprinidae family) and Salmo trutta (Salmonidae family) were the dominant species (> 65% of total fish catch) throughout the entire length of stream. The presence of rich benthic food, clear water, low turbidity (01-05 NTU), high DO (8.75-10.75 mg-l), and high water velocity (1.10-1.40 m-s) with characteristic rapids and cascades in upper reaches provides ideal habitat for the existence of native snow trout and exotic trout species. Few cat fishes, loaches, Tor spp. and lesser barils also have been reported during the study.