Impact of introduction of non- native fishes on indigenous fish fauna in freshwater reservoirs of Tamil Nadu

Abstract

Culture based fisheries has been intensively practiced in Tamil Nadu freshwater reservoirs by stocking seeds of non-native fishes for more than 50 years. Indian major carps, Common carp and Tilapia are the most important fishes regularly being stocked to enhance the fish yield. It was justified that stocking with seeds of non-native fishes fills the vacant niche untapped by native fishes. Many reservoirs an abode of valuable indigenous fishes have lost their fishery wealth consequent to introduction of alien fishes. Survey on fish landings conducted by CIFRI in Mettur reservoir, Tamil Nadu alarmingly revealed the disappearance of precious Cauvery carps. The landings of unstocked fishes declined to 67276 kg in 2002-2003 from 148452 kg recorded in 1993-94. Similar marked decline of native fishes, Wallago attu and Chela chela in Vaigai, Labeo calbasu in Peechiparai and mullets in Krishnagiri reservoir has been observed in Tamil Nadu. An ecological imbalance created by the culture based fisheries system needs to be addressed urgently by taking appropriate measures and framing fishery policies to conserve the biodiversity of natural water bodies. A social entrepreneurship approach should be developed to exploit the fish production potential of reservoirs without destructing the populations of native fishes.