Variations in Reproductive Characteristics among Oreochromis niloticus Populations of Three Ethiopian Rift Valley Lakes

Megerssa Endebu, Abebe Getahun and Misikire Tessema

Background and Objective: Nile tilapia (Oreochromis niloticus) populations within Ethiopian rift valley lakes are found at different fishery status and the fishes exhibited different phenotypic characters. The current study is aimed at investigating some reproductive characters of O. niloticus in Lakes Chamo, Koka and Ziway with respect to sustainability of their fishery and potential use in aquaculture. Materials and Methods: A total of 1,547 adult O. niloticus were sampled from commercial catches of the three lakes during May, 2018-2020. Length at sexual maturity (L₅₀), breeding seasons, fecundity and the relationship between fecundity and morphometric characters were analyzed. Results: The size at maturity (L₅₀) was high for O. niloticus population of Lake Chamo (23.48 cm), followed by that of Koka (21.91 cm) and Ziway (males 17.49 cm and females 16.00 cm); all the values lower than previous reports. The populations breed year round but peak activity varied among the lakes. The mean absolute fecundity (eggs/female) of O. niloticus populations were 1,321.8±342.9 for Chamo and 1,146.9±115.2 for Koka; both values significantly higher than 450.1±180.8 of Ziway (p = 0.00). The fecundity has positive relationship with total length, total weight and gonad weight. Conclusion: Decreases in size at maturity is sign of fishing pressures and environmental stresses, alarming for the need to implementation of proper management measures. With higher L₅₀ and fecundity value as desired reproductive qualities in aquaculture, populations of Chamo followed by Koka appear to be potentials for further genetic improvement.

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