Diversity, distribution and assemblage structure of fishes in streams of southern Western Ghats, India.

Diversity, distribution and assemblage structure of fishes were studied in 10 selected streams of southern Western Ghats. The sampling was performed between April 2001 and March 2002. Sixty species of primary freshwater fishes belonging to four orders, 13 families and 27 genera were recorded from the study area. Cyprinids were the most dominant assemblage members in all study streams. Maximum number of species, number of individuals and cyprinids were recorded from Thalayanai stream. More specialized forms Homaloptera santhamparaiensis, Glyptothorax madraspatanum, Noemacheilus guentheri, N. keralensis, N. semiarmatus and N. triangularis were recorded in Panniyar stream. High diversity was observed in Achankoil stream. Evenness index of similarity was uniform in all study streams. Similarity cluster analysis showed streams from nearby basins had similar faunal assemblages. Principal Component Analysis was performed to study the similarity of fish assemblages between the study streams. The analysis described clear pattern of segregation between Thalayanai and Karaiyar (east flowing) and Kallar and Achankoil (west flowing) streams. Thirty-nine Western Ghats endemic fishes were recorded from the study area. Current distribution and threats to endemic fishes are discussed.