HORMONAL SEX INVERSION IN THE COMMON CARP (CYPRINUS-CARPIO L)

Hormonal sex inversion was induced in genotypic females of the Israeli Dor-70 common carp line and ornamental common carp (koi). All-female progenies produced by either meiotic or mitotic gynogenesis were inves tigated in the experiments. Twenty-seven to 40-day-old fingerlings (me an initial weight of 2.8-14.5 g) were fed with a diet containing 100 p pm methyltestosterone for 40 days. The effectiveness of androgen treat ment depended on fish rearing conditions. The percentage of inverted m ales varied from 46.7 to 96.6% among fish reared in recirculation wate r systems, and from 20.0 to 43.8% among fish reared in tanks with runn ing water. The data obtained suggest that the weight of fish (rather t han their age) may be used as a practical criterion for determining th e appropriate period of androgen treatment.