EFFECTS OF DIETARY ESTRADIOL-17-BETA ON FEMINIZATION, GROWTH AND BODY-COMPOSITION IN THE JAPANESE EEL (ANGUILLA-JAPONICA)

1. Juvenile Japanese eels (Anguilla japonica) were fed on a diet suppl emented with estradiol-17beta (E2) at doses of 25, 50 and 75 mg/kg. Th e effects on growth, sex distribution and body composition were invest igated in two groups of gonadally undifferentiated stages (early and l ater juvenile stages). 2. Feminization (95-100%) was observed in all E 2-treated groups. 3. The growth rate of fish treated with 25 and 50 mg /kg E2 diet at the early juvenile stage was significantly increased. 4 . The amount of protein in muscle decreased and that of fat increased in the E2-treated groups except in the early juvenile stage fed with 2 5 mg/kg E2.