Plasma cortisol and sex steroid levels in Great Lakes coho salmon (Oncorhynchus kisutch Walbaum) in relation to fecundity and egg survival.

Plasma 11-ketotestosterone and cortisol levels in spawning male and female coho salmon (Oncorhynchus kisutch Walbaum) collected from a Lake Erie (Pennsylvania) stock were significantly lower (P less than 0.01) than in stocks of coho salmon at a comparable stage of sexual development collected from Lakes Ontario (two stocks) or Michigan. Plasma testosterone levels in female coho salmon from Lake Erie were significantly lower (P less than 0.01) than in females from Lake Ontario or Lake Michigan stocks. There were no significant differences in plasma testosterone levels in the males, or 17 beta-estradiol levels in male or female salmon of the four stocks sampled from the three study lakes. This apparent dysfunction in androgen and cortisol secretion in the Lake Erie stock is correlated with and may account for the low fecundity and poor expression of secondary sexual characteristics in that stock.