Effects of Different Hormones on Sex Reversal of Rainbow Trout (Oncorhynchus Mykiss Walbaum) and Production of All-Female Populations

Abstract

ABSTRACTThe sex reversion technique in fish is widespread in many countries. The development of these techniques is desirable because rainbow trout males reach their gonad maturity earlier compared to the females. A feeding trial was conducted to examine the supplemental effects of three hormones-17α-Methyltestosteron, 11β-hydroxyandrostenedione, 17α-Ethynyltestosterone on sex reversal and growth performance of rainbow trout. Control groups were fed with commercial diets for rainbow trout without hormones. These sex reversed functional males were reared for brood stock until they attained sexual maturity. Thereafter, normal rainbow trout eggs were fertilized with the sperms taken from sex reversed males for producing all-female populations. Also sex reversal ratio and growth performance were determined in hormone-treated groups.Examination of the results showed that 17α-Methyltestosterone was the most effective hormone treatment. The highest sex reversal ratio with 86.67±6.67% was observed in group treated with 3 mg/kg 17α-Methyltestosterone for 60 days. 11β-hydroxyandrostenedione and 17α-Ethynyltestosterone released lower rates and produced quite equal results. Also highest intersex ratio of 46.67±6.67% was recorded in group treated with 30 mg/kg 17α- Ethynyltestosterone for 40 days but the rate was below 20% nearly in all other groups. Even though 17α-Ethynyltestosterone seemed the best, the individuals with unaltered sex were observed in range of33.33±6.67% in group fed with 3 mg/kg 17α-Methyltestosterone for 30 days. It is very likely that the phenomenon is due to the short feeding period.