Capture fisheries has for decades contributed significantly to food security, employment and livelihoods. However, catches trends are indicating a major decline with commercially important indigenous species in the Great lakes fast disappearing. The study investigated the potential of cage aquaculture systems contribution towards the conservation of Lake Victoria native tilapiines. Wild brooders of Orechromis esculentus and Oreochromis variabilis were sourced from colonial dams and satellite lakes along the Lake Victoria basin, Kenya, and domesticated for mass multiplication at KMFRI Kegati Aquaculture Research Center-Kisii. To evaluate the performance, of the F1 generation of the native species, a 3x2x1 factorial l design with three replicates was implemented using cages in Lake Victoria. The stocking fingerlings (5±0.01g) was at a density of 30 fish/m³ and subjected to 40%, 35%, and 30% CP diets over a six-month period. The 40% CP diet, rich in fishmeal and soybean meal, was used in the early phase to support juvenile growth, followed by 35% and 30% CP diets in the mid and late grow-out stages, respectively, to match declining protein requirements and reduce feed costs. This step-down feeding strategy revealed that O. niloticus utilized the diets more efficiently than the native species, likely due to its domestication history and prior selection for aquaculture traits. Further, wild fish biodiversity around the cages was assessed at baseline, mid-term, and at the end of the experiment using gill nets. O. niloticus performed significantly better (185.39±0.27g) compared to O. esculentus (47.26±0.08g) and O. variabilis (46.03±0.12g). Meanwhile there was a signifiacant difference across species on survival with O. niloticus having the highest survival (88.5%) and the best FCR (1.77). The poor performamnce of O. esculentus and O. variabilis is due to adaption challenges under confinement and lack of a selection for aquaculture traits unlike O. niloticus. Therefore, there is an urgent need for continued research on the culture biology of these native species, alongside expanded propagation programs, to enhance their survival and support biodiversity restoration efforts in Lake Victoria.
Keywords: Cage aquaculture, Oreochromis variabilis, Oreochromis esculentus, conservation, Lake Victoria, growth performance, water quality, fish biodiversity, fatty acid profile.