Some Factors Affecting Contribution of Cichlid Species Etroplus suratensis and Tilapia rendalli to the Gill-net Catches of a Man-made Lake in Sri Lanka

Abstract

In the gill-net fishery of Pakakrama Samudra, a man-made lake in Sri Lanka, some factors affecting species composition of the commercial landings were studied from February 1985 to February 1986, with particular reference to the cichlid species, Etroplus suratensis and Tilapia rendalli. The proportions on the catches of a water beating technique, a modified gill-net fishing method, were found to be significantly different from that of normal gill netting. These differences in the catches of E. surantensis and T. rendalli are suggested to be due to their restricted movements, associated with reproductive behavior. The increase of catches of two cichlid species with elevation of water level may have been brought about by their aggregation in recently inundated peripheral areas of the lake to feed on macrophytes. The importance of stratifying data according to fishing method and mesh size of gill net in order to determine species composition in discussed. Using this method of analysis, annual fish yield in Parakrama Samudra in 1985 was estimated to be about 46 kg?ha-1.