Investigation of sexual maturity and change in gonadosomatic index of sex riversed rainbow trout (Oncorhynchus mykiss) treated by oral 17 alpha methyl testosterone

The study was carried out in the genetics and breeding resaerch canter of yasouj. All eye-stage eggs were used for the experiment using vertical hatching units to complete hatching. A standard commercial granule feed was used in all experimental groups. The experiment consisted of control treatment and one dose of hormone 17α-Methyltestosterone added to the diet at the rate of 3 mg per kg food by dissolving in 200 ml of 95% ethanol per kg feed.The use of oral administration of 17α-methyltestosterone (17MT) at 3 mg 17MT/kg of feed for 70 days following the onset of feeding to sex reverse rainbow trout ( Oncorhynchus mykiss ) to produce XX males is well established. Examination of the results showed that 17α- methyltestosterone was effective in sex riversed of rainbow trout. The results has shown in nearly 100% of the treated animals being males. The GSI index in female and male fish of control group were 0.04±0.1 and 0.07±0.01, respectively (Fig.3) and significantly different ( p ≤5%). But GSI index of 100% sex riversed male fish of MT treated was 0.06±0.01 and hadn,t significantly differene ( p ≥5%) with treated group ( genetically male and female).