Performance of GIFT strain of Oreochromis niloticus in culture-based fisheries in non-perennial reservoirs, Sri Lanka.
W.M.H.K. WIJENAYAKE, U.S. AMARASINGHE* AND S.S DE SILVA
The superiority of Genetically Improved Farmed Tilapia (GIFT) strain of Oreochromis niloticus has been demonstrated under intensive culture conditions in ponds and cages but its performance under extensive culture conditions and interactions with other cultured species, such as in culture-based fisheries, is unknown. In the present study, performance of GIFT strain in culture-based fisheries in reservoirs of Sri Lanka was evaluated on the basis of specific growth rate, survival, species interaction and biological productivity of habitat. Fourteen non-perennial reservoirs were stocked with carps and GIFT strain and fish yield of all species in the 14 reservoirs studied ranged from 53.4 to 1800.7 kg ha-1, which consisted of 0% to 32% of GIFT strain. Yield of GIFT strain varied from 0% to 188.3 kg ha-1 in the 14 reservoirs. Results of the analysis indicated that biological productivity of the non-perennial reservoirs had greater influence on carp yield than on yield of GIFT strain. Also, there was no significant difference (p > 0.05) between mean fish yields of GIFT strain and non-GIFT strain in culture-based fisheries of non-perennial reservoirs. High variability of specific growth rate of GIFT strain is evident in culture-based fisheries in non-perennial reservoirs. The GIFT strain, which requires supplementary feeding for achieving its maximum growth potential, may be incapable of competing with other species for natural food in the non-perennial reservoirs. As such, GIFT strain is not a suitable candidate for the development of culture-based fisheries in non-perennial reservoirs of Sri Lanka.