The Garhwal region of the Central Himalaya (in the Uttar Pradesh, India) offers an unique physio-topographic, climatic and environmental features. The glacial-snow-fed and non-glacial-fed or spring-fed rivers of the area makes the upper basin of the Ganga River system of North India (being characterized by low water temperature steep gradient fast water current, high turbulence etc.). There are 65 fish species (belonging to 9 families of teleosts) reported so far. Various biotic communities (planktonic, benthic, nektonic and neustonic), detritus, debris, sand particles are being used as food matters by herbi-, herbiomni-, carnivomni-, carni-, larvi- and piscivorous fishes. During recent years, hillstream environment has deteriorated owing to excessive deforestation, multipurpose river valley projects, over grazing, forest fires, modern tourism, over exploitation of natural resources.