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 investigated in the experiments. Twenty-seven to 40-day-old fingerlings (mean initial weight of 2.8-14.5 g) were fed with a diet containing 100 ppm methyltestosterone for 40 days. The effectiveness of androgen treatment depended on fish rearing conditions. The percentage of inverted males varied from 46.7 to 96.6% among fish reared in recirculation water systems, and from 20.0 to 43.8% among fish reared in tanks with running water. The data obtained suggest that the weight of fish (rather than their age) may be used as a practical criterion for determining the appropriate period of androgen treatment.