Western Ghats is one of the biodiversity hotspots of India with numerous native flora and fauna. Harangi reservoir (12° 29' 30" N 75° 54' 20" E) with a water spread area of 1910 ha at Full reservoir level (FRL) on Cauvery river system in Western Ghats harbours a good number of endemic ichthyofauna. Physico-chemical parameters of reservoir water like temperature, pH, specific conductivity, dissolved oxygen and total hardness ranged from 21.5-31.3 oC, 6.34-8.57, 48-119.5μs/cm, 6.86-9.48 mg/l and 18-50 mg/l, respectively and are within the favourable range for fisheries enhancement. However, better management techniques should be practiced in order to increase the productivity of this reservoir.
A total of 35 species belonging to 10 families and 6 orders were recorded from this reservoir. Limnetic zone of the reservoir reflects more faunal diversity than littoral zone. Based on temporal analysis highest diversity was recorded during post monsoon season followed by pre-monsoon and monsoon with Shannon diversity index values, 1.887, 1.51 and 1.457 respectively. Spatial diversity analysis showed that lotic zone of the reservoir has high diversity (1.745) followed by lentic (1.646) and intermediate (1.576) zones.
Our study indicates that 35% of fishes recorded from this reservoir falls under the threatened category. Recreationally important sport fishes like Tor khudree and Tor putitora, commercially important fishes like Wallgo attu, Ompok pabo, O. bimaculatus and Mystus malabaricus are under the threatened category. Exotic fishes, Oreochromis mossambicus, O. niloticus, Cyprinus carpio and Clarias gariepinus encountered in this reservoir may impact endemic fauna. Ornamental fishes like Chanda nama, Barulius gatensis, Pethia conchonius, P. ticto, Puntius sophore were also recorded from this reservoir. These economically important fishes need to be included suitably for species diversification through aquaculture and culture based fisheries. It is suggested to study the genetic diversity for conservation and stock improvement of this important endemic fishes.