Fish, one of the most important protein sources for human, is also an important vertebrate member of aquatic medium. Fisheries sector also contributes a major amount of the total economy of India. Fish diversity, an important indicator of the ecological status of any aquatic ecosystem (both lotic and lentic), is estimated by the use of different statistical approaches. Determination of relative abundance, habitat orientation score and trophic level score of the available fish species and also use of biotic index in any aquatic system depict the ichthyofaunal status with a clear indication of the vulnerability of the ecosystem. Owing to this, a study was conducted from January, 2012 to December, 2014 on River Churni, a major source of the surface water of Nadia district of West Bengal to measure the present status of species diversity and seasonal variation of assemblage of fish fauna. Data have been collected throughout the total span of investigation from major catchment sites of different parts (i.e., up stream, mid-stream, downstream) of the river. Studies have revealed that a total of 38 species of 7 orders and 17 families of fishes are there in the river. The number of available fish species has been found to be variable according to the season and part of the river. Trophic level score has revealed that omnivore fishes (34.78%) are predominant in upper stretch of the river and are followed by carnivore (30.43%), planktivore (26.08%) and benthic feeder (8.69%). In mid-stream, the trophic level score is found to be oriented in the following manner i.e., PL (33.33%)> OM (30.55%) > CA (22.22) > BE (8.69%). Apart from this, the values of Shannon- Weiner index (2.62 3.49), Simpson’s index (0.034-0.077) have indicated the more stable condition in downstream of the river than the upper parts. As, the river has been cited to have degrading ecological condition by many authors, results from this investigation will be helpful for the implementation of conservation ideas of the fish fauna in the river.

Keywords: Fish; River Churni; Ichthyofauna; Statistical Approaches; Biotic Index.