Effects of mesterolone on growth and sex-ratio of the Nile tilapia (Oreochromis niloticus Linnaeus)

MD Samsul Alam, Mohammad Khorshad Monwar


Mesterolone, an androgenic hormone, was fed to the sexually undifferentiated fry of Nile tilapia Oreochromis niloticus, for a period of 42 days at four different doses such as 50, 100, 150 and 200 mg/kg feed. At the end of the hormone feeding phase, the fry of the treatments fed on 50 and 100 mg/kg mesterolonetreated feed gained significantly higher length and weight than those of the fry fed on 150 and 200 mg hormone/kg feed and the control diet (0 mg/kg). A 100 % sex-reversal was obtained in the group fed on 200 mg mesterolonetreated diet. The sex-ratios of fish of the groups fed on diets containing 150 and 100 mg hormone/kg were found to be skewed towards male and were significantly different from that of the expected sex ratio of 1:1 in a normal population. On the other hand, the frequency of male fish of the group fed on 50 mg/kg mesterolone-treated and the control diet were not different from that of the expected frequency of 50 %. Some intersex fishes were also observed in the groups of fish grown from fry fed on lower doses of hormone (50-150 mg/kg feed).

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