Population dynamics and stock assessment of Oreochromis niloticus (Linnaeus) in the Kaptai Reservoir, Bangladesh

Abstract

Population parameters of Oreochromis niloticus (Linnaeus) was estimated using FiSAT software with length-frequency data collected from Kaptai Reservoir, Bangladesh. The von Bertalanffy growth parameters L and K of the species were 55.59 cm and 0.39/yr respectively. The annual rate of natural (M) and fishing mortality (F) were found to be 0.80 and 0.59 respectively. The estimated values for the exploitation rate (E) using the length converted catch curve and virtual population analysis were 0.42 and 0.258 respectively. Recruitment of this species was continuous with one peak per year. Emax was found to be 0.63. The present investigation clearly showed the under fishing (E<0.50) condition of O.niloticus in the Kaptai Reservoir. The estimated total length-weight relationship for the combined sex was found to be W = 0.0366TL2.844. The estimated annual stock, standing stock and MSY of O. niloticus in the Kaptai Reservoir were recorded as 126.25 MT, 68.47 MT and 47.59 MT respectively. The value of MSY is found to be higher than the annual catch (40.40 MT) indicating below fishing pressure on existing stock in the reservoir and that fishing pressure may be increased by about 16% to get MSY.