Ineffectiveness of Steroid Immersion Treatments for Sex Reversal of Brook Trout

Abstract

Immersion applications of androgenic steroids to sac fry of brook trout Salvelinus fontinalis were ineffective in inducing phenotypic sex reversal. Four experiments were conducted to test the effects of paired 2-h immersions in solutions of 17α-methyldihydrotestosterone (MDHT) at 1 or 3 mg/L and applied at times ranging from 1 to 25 d after completion of hatch. In a fifth experiment, similar tests were conducted with 0.4 mg/L solutions of MDHT, 17α-methyltestosterone, and trenbolone acetate. The experimental fish were of two types: normal mixed-sex fish and all-female gynogenetic fish. Phenotypic sex was determined by visual examination of the gonads when fish were sacrificed 6–8 months after initiation of feeding. In no experiment was there a significant increase in the percentage of males or a significant incidence of intersex gonads among treated fish. A generally low level of sterile and partially sterile fish was observed among control fish of both types, and these percentages tended to increase among treated fish.