Growth and reproductive development in fall chinook salmon: effects of sex hormones and their antagonists

• Published in: Aquaculture (Netherlands) Vol. 26; no. 3
• Main Authors: Schreck, C.B. (Oregon State Univ., Corvallis (USA). Oregon Cooperative Fishery Research Unit), Fowler, L.G
• Format: Publication
• Language: English
• Published: 01.01.1982

Testosterone, 17alpha-methyltestosterone, testosterone propionate, and diethylstilbesterol (DES) plus clomiphene citrate (an antiestrogen) were evaluated as potential growth promoters in juvenile fall chinook salmon (Oncorhynchus tshawytscha), and antiandrogens cyproterone acetate (1,2alpha-methylene-6-chloro-delta4,6-pregnadiene-17alpha-ol-3,20-dione-17alpha-acetate) and flutamide (4'-nitro-3'-trifluoromethylisobutyranilide) were investigated as possible inhibitors of the androgenic effects of these anabolic steroids. Test compounds were added to the feed of salmon for 22 weeks for the 1976 brood and 16 weeks for the 1977 brood. All androgens and DES plus clomiphene citrate accelerated growth. High levels of methyltestosterone caused precocious male development and subsequent reduced grwoth. Flutamide did not inhibit the androgenic effect of methyltestosterone, but may have moderated the effect of testosterone. Gonadal histology revealed the presence of intersex fish in groups treated with low levels of methyltestosterone or this steroid plus flutamide. Undifferentiated gonads were present in some fish treated with methyltestosterone, testosterone, or cyproterone acetate. Higher levels of testosterone tended to increase the frequency of males with well developed testes; neither antiandrogen inhibited these maturational effects. Testosterone administered at between 5 and 10 mu-g/g feed appears to be the most likely candidate compound for use to promote growth without affecting male sexual development in chinook salmon.