Search   in
between years and
Mortality, exploitation rate and relative yield of Rastrineobola argentea (Pellegrin 1904) in the Winan Gulf of Lake Victoria (Kenya)
J.O. Manyala, E. Vanden Berghe and S. Dadzie

The mortality rates of R. argentea in the Winam Gulf of Lake Victoria were quite high with a range of total mortality coefficient (Z) of 1.766 - 2.860 yr-1 while the fishing mortality coefficient (F) was 0.966 - 1.984 yr-l. Mean Z/K value was 3.749 ± 1.104. Fmax as 0.82 ± 0. 13 yr-1 while F0,1 , was 0.51 l± 0.07 yr-l. The current exploitation rate (ECUR)was 0.551 - 0.653 which was above the maximum sustainable yield (EMSY= 0.460 - 0.483), maximum economic yield (EF0,1= 0.348 - 0.365) and optimum exploitation rate (Eopt = 0.5) by 5.1 - 74%. Two-way analysis of variance (ANOVA) revealed no significant differences between stations nor sexes in 90% of the population parameters. A general reduction in asymptotic length (L) of R. argentea was realized in the Winam Gulf while the stock is currently overexploited. Dagaa fishery in the Winam Gulf of Lake Victoria is commercially important as a source of poultry feed, fish feed, cattle feed and human food. Rational exploitation of this fishery could be possibly achieved through correct management policies including the fisheries cooperative societies, licencing of nets in addition to registration of boats and strict observation of closed seasons.

Keywords: Rastrineobola argentea, Lake Victoria, growth, mortality, exploitation, yield per recruit.
Contents of this volume Sci. Mar. 59(3-4) : 555-563 Back PDF
Please, send comments to
ICM (CSIC) - Passeig Marítim de la Barceloneta, 37-49. E-08003 Barcelona (Spain)