THE EXTENT OF FISH HARVEST ON THE COMMERCIAL FISHERY OF LAKE HAWASSA, ETHIOPIA
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Abstract
The sustainability of a given fishery is a function of the number of sexually matured fish present. If there is intensive immature fishing, the number of fish reaching at stage of recruitment will decrease, which in turn results in lower yields and biomass. This study was conducted to estimate the extent of immature fishing on the commercial fishery of Lake Hawassa. A random of 962 Oreochromis niloticus and 672 Clarias gariepinus were sampled from the fishermen catch for two weeks from May 15 to 30/2011 which was peak spawning season for both O. niloticus and C. gariepinus. The maturity of the sampled fish was determined by visual examination of developmental stages of gonads based on their sizes and the space they occupy in the body cavity of fish. Results showed that there was heavy immature fishing as high as 77.8% in C. gariepinus, however, slight immature fishing (22.7%) was documented for O. niloticus. Lengths at first sexual maturity of male and female C. gariepinus were 55.4 cm and 53.3 cm, respectively and, 20 cm and 20.8 cm for female and male O. niloticus, respectively. Thus, immature fishing of C. gariepinus should be stopped as soon as possible since only one-fifth of the population has the chance to breed and replenish the stock before it is caught. Widening the currently used minimum mesh size from 8 cm to 10 cm is recommended to avoid immature fishing.
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