PRODUCTION OF NATURAL “XY” FEMALE OF NILE TILAPIA “OREOCHROMIS NILOTICUS” BY THERMAL MANIPULATION IN EGYPT

Nile tilapia (Oreochromis niloticus), a crucial freshwater fish for aquaculture, requires mono-sex culturing to prevent unwanted reproduction during grow-out, making sex control a crucial issue in aquaculture. The hormone 17-α-methyltestosterone is typically employed to generate phenotypic males in the mass production of all-male fingerlings. The extensive use of substantial amounts of sex reversal hormones in hatcheries may present health hazards to workers and ecological risks to adjacent areas. This study illustrates breeding strategies to produce genetically all-male tilapia without the use of sex hormones. This study examines the intricate sex determination system of Nile tilapia, influenced by genetic factors and temperature interactions in domestic populations. Sex reversal can occur due to feminizing temperatures experienced by fry during their sex differentiation period in shallow waters, and/or due to the impact of minor genetic variables. The 3-day post-fertilization Nile tilapia fry was reared in Agromar farm at 17-20 °C for 60 days to induce XY female sex reversal, after which the tail fin (n=21) was harvested for genotyping and cytogenetic investigation. Results indicated that there 30% of Tilapia were reversed to XY females. The present study may provide an important unique foundation for developing genetic male tilapia XY females by natural sex reversal in Egypt.