Gillnetting for small indigenous cyprinids in a Sri Lankan reservoir where culture-based fisheries are practiced

In Sri Lankan reservoirs, small, indigenous fish species (SIS) are abundant and can be differentially exploited using small mesh (15-38 mm stretched mesh sizes) gillnets without any detrimental effects on the cichlid fisheries. However, in the recent past a paradigm shift in the reservoir fisheries of Sri Lanka is observed from total dependence on exotic cichlids to exploitation of exotic carps, stocked in reservoirs for the development of culture-based fisheries (CBF). As fingerlings of Chinese and Indian major carps and common carp are regularly stocked in reservoirs for the development of CBF, it is essential to investigate the potential impact of the use of small mesh gillnets to catch SIS on stocked fish fingerlings on CBF. In the present study, small mesh gillnets were used to exploit SIS during September 2011 to March 2013 when carp fingerlings were stocked in Chandrika wewa, Sri Lanka. The results revealed that no carp fingerlings (except 2 specimens of Indian carp species) were caught in any of the fishing trials with small mesh gillnets. As juvenile fish and stocked fish fingerlings occur in shallow littoral areas of reservoir, and as small mesh gillnets are laid at the depths ≥ 1.5 m, there is a habitat segregation of these two categories of fish. It is therefore possible to introduce a subsidiary fishery with small mesh gillnets to exploit SIS, which can co-exist with CBF in reservoirs of Sri Lanka.