Environmental conditions and natural food resources for commercial fish production in the valley dams of Mbarara District, Uganda
2010
Kemigabo, C.,UNESCO-IHE Inst. for Water Education, Delft (The Netherlands) | Adamek, Z.,Jihoceska Univ., Ceske Budejovice (Czech Republic). Jihoceske Vyzkumne Centrum Akvakultury a Biodiverzity Hydrocenoz
The Mabira, Kyenshama and Rushozi valley dam reservoirs in the Mbarara District, Uganda, provide suitable environmental conditions for fishery exploitation and controlled fish farming and/or ranching management. Physicochemical characteristics were correlated to primary production in Rushozi and Kyenshama and to altitude and geology in Mabira. All dams were eutrophic with nitrogen likely to be limiting in Mabira and Rushozi and phosphorus in Kyenshama. Phytoplankton abundance (with Chlorophyceae and Cyanobacteria dominance) was significantly higher in Rushozi. Abundance of zooplankton and benthic macroinvertebrates was similar across dams. Oreochromis niloticus and Clarias gariepinus were the dominant and available culture species. Their condition based on length and weight correlation was highest in Rushozi dam (1.86+/-0.18 and 0.63+/-0.07 for tilapia and catfish, respectively) and coincided with the highest oxygen, temperature, feed uptake and phytoplankton abundance and biomass (according to chlorophyll-a concentration). Detritus, plant material, and phytoplankton were the most important diet items for both tilapia and catfish. However, the level of justifiable feed coincidence was very low amounting to 2.9% in phytoplankton. The majority of feed coincidences concerned low valued feed items - detritus (12.7%) and plant material (14.7%).
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