Observations on the fisheries, growth and mortality rate of Oreochromis niloticus (tilapia) in the Nyanza Gulf of Lake Victoria
Oreochromis niloticus forms the third most important commercial fishery in Lake Victoria after Lates niloticus and Rastrineobola argentea. Because of its commercial importance as a cheap source of animal protein, a study of its landing trends, growth and mortality rates was conducted to assess the state of its stock in the lake and recommend guidelines for its exploitation and management. To arrive at the trends, landing data between 1976 and 1989 were analysed. For the estimation of the growth and mortality rates, length frequency data were collected from trawl surveys conducted fortnight between Sseptember, 1989 and August, 1990 in the Nyanza Gulf. The results show increased landings during the study period, with a higher percentage landed in the open waters of the lake. The length-frequency results show that O. niloticus is a slow growing fish which attains a great asymptotic length of 61.3 cm, a growth constant K of 0.35 yr super(-1) and a high growth performance index phi of 3.12. The total, natural and fishing mortality rates were estimated at 1.71 yr super(-1) and 0.72, 0.99 yr super(-1) respectively. It is concluded from these studies that O. niloticus has a high growth performance index attaining larger sizes and if well managed, its fishery may flourish and sustain the protein supply to the people living around the lake.
- Conference Papers