Ecology, Environment and Conservation Paper

NICHE HETEROGENEITY IN VULNERABLE HABITAT CONDITIONS MAINTAINS AND AMPLIFIES FISH DIVERSITY IN RIVERS OF SOUTH BENGAL, INDIA

Arpita Rakshit and Sovan Roy

Abstract

One hundred and thirty seven fish species belonging to 12 orders, 39 families and 91 genera have been sampled from non-saline portions of 13 different rivers and associated lentic bodies. Order Cypriniformes contributes 28.467% of total species. Orders Perciformes and Siluriformes contribute to 26.277% and 24.087% respectively. Other orders contribute less than 10% of the total fish species. Beloniformes has contributed to 0.729 % only. Out of 137 species, 36 species, i.e. more than 26% have maximum niche expansion as they are common to all rivers. Altogether 17 alien fish species have established across the rivers. Per cent indices of Diversity, Equitability, Richness and Concentration of Dominance ranged from 26.31 to 54.54, 7.05 to 10.69, 10.39 to 23.86 and 5.12 to 10.53 respectively. Increase in diversity has been ensured by the increase in species richness only, without any significant change in species equitability. This suggests for vulnerable communities with spontaneous adaptive changes plus survival of existing species through heterogeneous niche spaces in face of habitat fragility, as evidenced by many co-existing genera with multiple species, subspecies, varieties, ecotypes etc.