The study is based on work done in a part of the Western Ghats, located along the southwestern coastline of the Indian subcontinent. This region, though being part of a biodiversity hotspot has been entirely neglected with regards to studies on the freshwater fauna of the region. Four of the west flowing rivers (Kali, Aghanashini, Bedti and Sharavati) were chosen to study the diversity, distribution and ecology of the freshwater fish communities of these rivers. The main objectives of the thesis were - 1)To study the diversity and compositions of the fish species found in these four rivers 2) The distribution patterns of species, the status of these species in terms of their rarity, endemicity, or being endangered and their relation to environmental gradients 3) To understand the correlation between morphological features with the habitat and feeding ecology of some of these species and 4)To study the kinds of human disturbances that might be affecting fish communities and the changes in species compositions caused due to these disturbances.
Fish sampling and data on physical and chemical parameters were done over a period of two years (December 1996 – April 1999) where 24 sites pre-selected for sampling on a regular basis were chosen and were sampled at different times of the year, and during both day as well as night.
A total of 10,771 individuals belonging to 92 species were identified. 25 species from this collection (27.2 %) are endemic to the Western Ghats. Out of a total of 25 families, the Cyprinidae is the most dominant group, represented by 45 species. A new species of catfish, Batasio sharavatiensis, was also recorded (Bhat 2001; Bhat 2003; Bhat, 2004). Bedti and Aghanashini are the most similar in terms of their species composition, while Sharavati is the least similar to the other three rivers. Comparisons of species composition at the regional scale show that similar regions on different rivers are closer to each other in their fish species composition as compared to different regions on the same river (Bhat, 2003).Changes in species richness as well as composition are found, along the upstream to downstream gradient in rivers, with downstream regions showing higher species richness than the upstream regions. These are associated with changes in stream habitat and stream physical characteristics (Bhat, in press).The Index of Biotic Integrity, a method used for ranking sites according to the extent of human disturbances and their effect on fish community richness and composition, was used to score and rank 16 sites located on these rivers. The results of this study confirm that some of the sites on the most polluted spots on Kali (e.g. Dandeli and Bommanahalli) are the most affected by disturbances, while study sites on Aghanashini as well as Bedti seem to be fairly undisturbed in terms of their fish community composition. Thus, this method can be used as a preliminary study for preparing conservation plans for a region, using fish communities as indicators of disturbance. (Bhat, in preparation).
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References:
Anuradha Bhat (2001). New report of the species, Horabagrus brachysoma in the Uttara Kannada District of Karnataka. Journal of the Bombay Natural History Society, Vol. 98 (2): 294-296.
Anuradha Bhat and K.C. Jayaram (2004). A new species of the genus Batasio Blyth (Siluriformes:Bagridae) from Sharavati River, Uttara Kannada, Karnataka State. Zoos' Print Journal, 19 (2): 1339 - 1342.
Anuradha Bhat (2003). Diversity and composition of freshwater fishes in streams of Central Western Ghats, India. Environmental Biology of Fishes, 68: 25-38.
Neelesh Dahanukar, Rupesh Raut and Anuradha Bhat (2004). Distribution, endemism and threat status of freshwater fishes in the Western Ghats of India. Journal of Biogeography, 31: 123-136.
Anuradha Bhat (2004). Patterns in the distribution of freshwater fishes in rivers of Central Western Ghats, India and their associations with environmental gradients. (Hydrobiologia, in press)