Sex Reversal of Black-Chinned Tilapia (Sarotherodon melanotheron) Fry Using 17α-Methyltestosterone

This study was conducted to determine the effective dose of 17α-methyltestosterone (MT) that produces all-male fry of black-chinned tilapia, Sarotherodonmelanotheron. Five concentrations: 0, 30, 60, 90 and 120 mg 17α-methyltestosterone (17α-MT) per kilogram feed were prepared using the ethanol evaporation method,and administered orally to black-chinned tilapia fry for 28 days in triplicate aquarium glass tanks. After the treatment period, triplicates of 60 fry from each treatment were stocked in hapas and further cultured in freshwater ponds. They were fed with commercial fish feed ad libitum. Thesex ratio, growth performance and survival were evaluated after 60 and 180 days.At the end of the 60-day period, the sex ratio of 30 fish from each treatment was determined by using the gonadal squash method. The remaining 30 fish from each treatment were grown further for 180 days and their sex ratio determined using the genital papillae. The results demonstrated that 17α-methyltestosterone was effective in producing phenotypic male in S. melanotheron. However, in both 60-day and 180-day experiments, no treatment gave 100% male population. The 90 mg/kg MT yielded the highest all-male fish of 84.13%, highest survival of 70% and highest final mean body weight of 103.99 ± 7.92 g.