Lake Jipe, straddling the Kenya-Tanzania border, is experiencing significant ecological degradation due to climate change, habitat modification, pollution, and the introduction of non-native species. These factors have critically endangered the endemic Jipe tilapia (Oreochromis jipe), which has a restricted range and declining populations. Notably, the introduction of O. niloticus and O. esculentus has led to the displacement of O. jipe and potential hybridization, threatening its genetic integrity.
This study investigates the hybridization potential of O. jipe with introduced tilapia species under controlled aquaculture conditions. A total of 144 mature brooders (100–120g) were randomly selected and paired in a 1:2 male-to-female ratio across different combinations: O. niloticus (♀) × O. niloticus (♂), O. niloticus (♂) × O. jipe (♀), O. jipe (♂) × O. niloticus (♀), and O. jipe (♂) × O. jipe (♀). Fish were fed a 35% crude protein diet at 5% of their body weight daily, divided into three feeding sessions. After 28 days, fry were counted and reared separately based on their cross type.
Findings revealed that pure lines of O. esculentus, O. niloticus, and O. jipe spawned by day 28, while crosses between O. esculentus and O. niloticus spawned by day 34. Crosses involving O. jipe and O. niloticus took longer to spawn and produced fewer offspring, suggesting that O. jipe may hybridize under stress. Growth performance varied among the different crosses, with no consistent weight gain patterns observed. Morphological differences were noted among fingerlings, but gender identification at this stage was challenging.
The study concludes that O. jipe can hybridize with introduced species under controlled conditions, and the hybrids can survive in aquaculture settings. However, the reproductive viability of these hybrids remains to be ascertained. Understanding these dynamics is crucial for developing conservation strategies, and controlled aquaculture of O. jipe and its hybrids could serve as a conservation tool, provided that measures are taken to prevent unintended genetic mixing in the wild.
Key words. O. jipe, hybridization potential, morphometry, conservation