Reproduction in Male Salmonids with Special Reference to the Problems and Control of Maturation in Fish Culture
The commercial problems accompanying the sexual maturation of male salmonids include a reduction in growth rate, the appearance of secondary sexual characteristics and changes in body composition. Information is presented on the development and extent of these changes among maturing rainbow trout and the endocrine control system by which such effects are controlled is reviewed. In particular, the roles of the naturally occurring androgens, testosterone and 11l-ketotestosterone, are examined. When administered to immature rainbow trout 11-ketotestosterone was more potent in inducing male secondary sexual characteristics, while testosterone exerted a greater depression of dry matter digestibility. Changes in this latter parameter are suggested to be an important component of the decreased food conversion efficiency observed in mature fish...
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