17α-Methyltestosterone can induce masculinisation and sterilisation in amur carp Cyprinus rubrofuscus Lacepede 1803

Abstract

To find a suitable solution to the problem of early sexual maturation and unwanted reproduction during grow-out, the present study was aimed at production of sterile or monosex population of Amur carp through endocrine manipulation. In this investigation, 24-day-old Amur carp fry were fed with diets containing 17α-methyltestosterone (17α-MT) at dosages of 200-1000 ppm for 30 d. While 17α-MT incorporation at 400 ppmresulted in complete masculinization, 600 ppm induced 100% sterilization. 17α-MT at 200 ppm induced the production of intersex and sterile fish. At 800 ppm, it produced 8.33% male, 8.33% female and 83.34% sterile fish, whereas 1000 ppm yielded 63.63% male, f9.10% female and 27.27% sterile fish. After 168 d post-treatment rearing, increase in fish weight was 16.01- 233.15%, over control. Loss of weight due to evisceration was 8.75-12.43% in control, while it was 7.31-9.78% in sterile fish, indicating the availability of more edible meat in the latter. MT-treated carp showed a slight variation in survival, gonadosomatic index (GSI), hepatosomatic index (HSI), viscerosomatic index (VSI) and condition factor. The histology of gonads revealed normal development of ovary and testis in control fish, but in 17α-MT treated fish the gonadal development was either normal or abnormal in male and slightly suppressed in female. Intersex fish had both ovarian and testicular tissues, while sterile fish possessed mostly connective tissue.