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Not Available1. Three classes of habitat used by groups of fish species classified as conservation andmanagement priorities were developed for the Gerua River (also known as the Girwa River, KarnaliRiver) in the Ganges river basin. This river is large (mean annual discharge ca 1500 m3s1,upto900 m wide), surrounded by protected lands of India and Nepal, and upstream of major diversionsand river alterations. 2. Fish and habitat sampling was conducted at 45 sites from 2000 to 2003. Data were analysed for2172 fish of 14 species. Species and life stages found occupying a statistically distinct subset of theriver habitats were grouped to identify classes of river habitat for conservation. 3. Most species and life-stage groups specialized on specific habitat conditions revealed bymultivariate analyses of variance and a principal component analysis. The most numerous anddiverse group (six species, 15 life stages) was associated with deep depositional habitats with sandysubstrate. Two species covering three life stages were primarily oriented to erosional habitat markedby fast current velocity with pebble and cobble substrate. A third group of three species of adults andjuveniles were intermediate in habitat use. 4.River conservation for fish faunas should maintain both erosional and depositional channel habitats with depths, substrates, and current velocity inclusive of the ranges reported. The erosional and depositional nature of the key habitats requires that rivers be maintained with flows capable of channel-forming functions.Not Availabl