Diversity and composition of freshwater fishes in river systems of Central Western Ghats, India

The Western Ghats ( India) is a region of high biological diversity and endemicity of terrestrial fauna, but very little is known about its freshwater species distributions. Four rivers, Sharavati, Aghanashini, Bedti and Kali, of the central Western Ghats were studied for their fish diversity and composition. A total species richness of 92 species ( and an endemicity of 25%) was reported. A comparison of expected species richness (SR) estimates using different statistical estimators was made - these showed the expected SR to be in the range of 92 - 120 species. Many of the species were found to be shared with those belonging to the southern Western Ghats, but the study also unearthed new findings in terms of description of a new species and extension of the known distribution range of some of the species. The study at varying spatial and temporal scales also showed that while the rivers are very similar to each other in terms of the SR values, they do vary with respect to the species composition. Species compositions across upper ( or lower) reaches of these rivers were found to be more similar to one another than the upstream and downstream reaches in the same river. Temporal patterns, with regard to diurnal activity of fishes were studied. These showed that of the 72 species collected at night, 29 were exclusive to night sampling. Though much of the information of the feeding and habitat preferences of the fishes in this region is lacking, it is speculated that the differences in their activity patterns could be related to feeding and predator avoidance.