Introduction

The freshwater fish family, Balitoridae has been divided into two sub-families; Balitorinae and Nemacheilinae. Balitorinae consists of genera Bhavania, Homaloptera, Travancoria and Balitora, whereas Aborichthys, Triplophysa, Acanthocobitis, Yunnanilis, Neonemacheilus, Nemacheilichthys, Oreonectes, Longischistura, Physoschistura, Schistura, Mesonemacheilus and Nemacheilus belong to the Nemacheilinae. Of these, Schistura McClelland, 1838 has the largest assemblage of Nemacheiline species (Jayaram, 1999), which inhabits mainly hill streams, waterfalls and also penetrates into sub-terranean region (Vidthayanon, 2003), having wide distribution throughout South, Southwest and Southeast Asia. Western Ghats of India with a distinct biogeographical regime, has six taxa, namely S. semiarmatus, S. denisoni denisoni, S. nilgiriensis, S. kodaguensis, S. denisoni mukambbikaensis and S. denisoni pambaensis (Jayaram, 1999). Recent discoveries of fish species in Western Ghats conforms Dahanukar et al. (2005) highlight that there are many more unexplored species in the region, which requires detailed field investigations.

Ichthyodiversity and species distribution studies carried out in Sharavathi river basin, Western Ghats (Fig. 1) covering all seasons and microhabitats over a period of 36 months has led to the discovery of two new species of Schistura in ecologically sensitive habitats as well as provided insight into habitat preference of many endemic and rare species.