The fish community of the Bhadra reservoir in relation to physic-chemical parameters was studied by monthly samples taken from June-2004 to May-2005. This water body is situated at 13o42| N latitude and 75o38| E longitude located near Lakkavalli town of Chikmaglore district, Karnataka and the confluence of the Bhadra River. The water of the reservoir is used for producing electricity, fishery and tourism activities. Fish collections were done with gillnets of standardized dimensions with several mesh sizes. 33 fish fauna identified during the study belongs to Cyprinidae 18 species, Channidae 2 species, Bagridae and Siluridae with 3 species and a species each of Mastacembelidae, Ambassidae, Cichlidae, Claridae, Notopteridae, Cobitidae and Heteropneustidae. Besides identification, relative occurrence and economic importance of fishes are discussed. All fishes are useful as food fishes except Ambassis, Puntius and Gambusia, which are useful as ornamental and larvicidal fishes. The species diversity is peak in post monsoon, coinciding with favorable conditions such as sufficient water and ample food resources. The diversity was low in premonsoon probably due to the shrinkage of the water spread of the reservoir. The high value of dissolved oxygen coupled with low biochemical oxygen demand and other nutrient levels indicate that the water body is moderately oligotrophic in nature. The factors responsible for declining population of fish species is discussed in detail. To save this diversity and to develop a sustainable fishery practices and proper documentation leading to diversity information system is an urgent need.