An initial study evaluated the effect of dietary administration of the androgen 17∝-methyltestosterone 40 mg kg<sup>-1</sup> on the growth and survival of Oreochromis niloticus fry, held at high density (1000 m<sup>−2</sup>), in tanks and in nylon, fine-mesh hapas. Treated and control fry were nursed and on-grown in ponds to determine their subsequent growth, survival, sex ratio and recruitment. A second study investigated the effect of increasing stocking density (1000-5000 m<sup>-2</sup>) on the growth, survival and sex ratio of fry, hormone-treated in hapas, with a higher dose of androgen (60 mg kg<sup>-1</sup>). In the first study, the androgen had no significant effect on growth and survival of fry during the treatment period and produced mean sex ratios of 98.4% male in tanks and 95.4% in hapas. Growth was slowest for fry held in tanks, but both these and those held in hapas had significantly lower (P-2) in hapas. Compensatory growth, during 14-day post-treatment nursing and early grow-out in ponds, negated these significant differences. Subsequent grow-out in ponds for 112 days yielded some significant (P-2) of fry, hormone-treated in hapas, increased the efficacy of sex-reversal up to 99.4% male but resulted in decreased growth and survival.
Mair, G.C.; Vera Cruz, E.M. Conditions for effective androgen sex reversal in Oreochromis niloticus (L.). Aquaculture (1994) 122 (2-3) 237-248. [DOI: 10.1016/0044-8486(94)90513-4]