HABITAT CHARACTERISTICS, FORAGING ECOLOGY AND GROWTH PERFORMANCE of Oreochromis niloticus baringoensis IN TURBIDITY-STRESSED LAKE BARINGO, KENYA

The impact of excess sediment loading and turbidity on the population and biodiversity of fish in the aquatic systems in the tropics has received scanty attention. In Lake Baringo, there has been no detailed study on the effect of sediment loading and turbidity on the fish despite the fact that sediment loading is hypothesised to be one of the main causes of reduced fish size, population and species in the Lake. The aim of this study was to analysed the effects of sediment loading and turbidity on the foraging ecology and growth performance of Oreochromis niloticus baringoensis. Samples were collected from the three delineated sites that varied in turbidity levels. The samples were collected monthly from December 2000 up to May 2001. During each sampling bout triplicate samples were collected from each site. Temperature, turbidity, Total Dissolved Solids (TDS), conductivity, dissolved oxygen (DO) concentrations and saturations and pH were measured. Plankton and benthos samples were collected using plankton net and a grab sampler, respectively, for the analysis of species composition while the fish were collected using a gill net for biometrics and the analysis of the gut contents. TDS was significantly different among the three sites (one-way ANOVA, F (2, 105) =26.61, p<0.001). There was a highly significant difference in the water temperature among the three sites (one-way ANOVA, F (2, 105) =7.40, p<0.001). Secchi depth was significantly different among the sampling occasion (one-way ANOVA, F (5, 102) = 6.66, p<0.001). Turbidity was significantly different among the site (one-way ANOVA, F (2, 105) = _ 156.05, p<0.01). DO% saturation was significantly different among the three sites (one-way ANOVA F (2, 105) =20.61, p<0.001). Conductivity was significantly different among the three sites (one-way ANOVA F (2, 105) = 12.79, p<0.001). pH was significantly different among the three sites (one-way ANOVA, F (2, 105) =8.39, p<0.001). Total length of fish was found to be significantly different among the three sites (one-way ANOVA F (2, 136) = 10.20, p<0.001). The fish weight was significantly different among the three sites (one-way ANOVA F -(2, 137) =7.84, p<0.05). Condition factor (k) for the fish was significantly different among the three sites (one-way ANOVA F (2, 136) =6.37, p<0.05). Results of this study bring into focus important aspects of the tropical lakes that are faced with siltation and turbidity. Turbidity has been shown as one of the main drivers of limnological problems. Others include high levels of pH, total dissolved solids, temperature and conductivity, which are all intertwined with levels of turbidity. It is recommended that in order to increase fish production reduction in turbidity is necessary to allow increases primary production. There is urgent need to enhance mitigation strategies that include reforestation of the highland water catchment areas to reduce siltation and sedimentation.