Plasma 11-oxotestosterone and gonadotrophin in relation to the arrest of spermiation in rainbow trout (Salmo gairdneri).

Plasma gonadotrophin (GTH) and 11-oxotestosterone levels have been studied in relation to sperm production during the last weeks of the spermiation period. The level of 11-oxotestosterone decreased in parallel to sperm production (coefficient of correlation: p = 0.59; P less than 0.01) and reached its lowest values (mean +/- SE = 0.33 +/- 0.19 ng/ml; n = 11) when spermiation was over. No significant variations were found in GTH levels; however, there was a slight positive correlation between sperm production and GtH levels (p = 0.39; P less than 0.05).