Seasonal dynamics of ichthyodiversity in a hill stream of the Darjeeling Himalaya, West Bengal, india

Abstract

The small torrential spring-fed hill-stream Relli in the Darjeeling Himalaya of West Bengal was studied from March 2007 to February 2009 to assess seasonal dynamics and diversity of fish populations. The study revealed that the stream sustained 25 rheophilic cold water fish species from 15 genera and five families having ornamental, food and sport value. Seven omnivorous species were abundantly found, and the array of juveniles and sub adults suggests this stream is used as a breeding and nursery ground for some species. The stream harboured fish with unique modifications such as adhesive structures. Analysis of monthly data indicate that abundance and diversity indices increased slightly during April–May and sharply during October–November, indicating significant seasonal variations with the low diversity observed during monsoon months reflecting environmental stresses. Evenness was high in all sampling sites, and inversely related to the dominance index of ichthyofauna. The density and diversity of fish assemblages along the gradient of the stream may be interrupted due to anthropogenic disturbances. Our study provides baseline data which may be helpful for conservation and management of fish species, and in formulating fishery policy.

Keywords

• Catch per unit effort (cpue), hill-stream relli, ichthyodiversity, population size, species diversity index.