Production of Hormone-induced Supermale of Genetically Improved Farmed Tilapia (GIFTYY) in Bangladesh

A series of experiments were conducted to produce YY-supermale GIFT strain of tilapia in Bangladesh first, through optimization of feminizing hormone, Diethylstilbestrol (DES) to produce 100% female tilapia. The feminized female tilapia (XY) obtained from 150 mg/kg feed treatment were reared, tagged and bred individually. About 36% (4 out of 11 fish) of the treated fish became sex reversed female and it was confirmed by sexing their offspring, produced through crossing with genotypic male (XY), using aceto-carmine gonad squashing method that resulted in 75% male and 25% female. Since the 75% male offspring are supposed to contain 25% YY male, half of the offspring of each sex reversed females were feminized using DES at the same dose (150 mg/kg feed) to produce YY female by reversing the sex of the 25% YY male offspring. The stock that contained 75% male offspring was kept as it contained theoretically 25% YY male. The other half of the same stock (feminized half) that contained 25% YY female was also kept. Then the all of the individual male and female of such stocks were bred individually and identified the individual YY male and YY female by observing the sex ratio of their offspring as YY male or YY female that produced 100% genotypic male offspring in mating with genotypic female and male, respectively. A total of 106 fish from the non-feminized stocks were bred, 15 of them were identified as YY male but only 4 fish produced 100% male and the rest produced 80.12% to 97.18% male. Similarly, 45 fish from the feminized stocks were bred, 8 of them were identified as YY female but 3 of them produced 100% male and the rest produced 93.33% to 97.77% male. Finally the identified YY males and YY females were crossed to produce 100% YY supermales and thus the objectives were achieved.