Effects of oral administration of 17α-methyltestosterone and 17β-estradiol on gonadal development in common carp, Cyprinus carpio L.

The effects of oral administration of 17α-methyltestosterone (17α-MT) and 17β-estradiol (17β-E2) on the gonadal development of common carp were investigated during periods of 5 weeks between 3 and 15 weeks after hatching. Administration of 50 ppm 17α-MT in the food between 6 and 11 weeks after hatching resulted in 92.7% males. Earlier or later treatments with 17α-MT at concentrations of 50 and 100 ppm of hormone in the food resulted in high percentages of sterile fish. Administration if 17β-E2 failed to induce female gonads in any of the periods tested and irrespective of the concentrations of hormone used. Gonad weight and gonadosomatic index of both males and females decreased with increasing doses of 17β-E2, indicating that the hormone had been absorbed by the fish. For hormonal sex control in other fish species it is recommended to apply hormone dosages which are related to body weight and not to body weight gain.