Hormonal content of commercial fish diets and of young coho salmon ( Oncorhynchus kisutch) fed these diets

Abstract

Hormonal content of several varieties of commercial fish diets was determined by radioimmunoassay: Biomoist starter #2, Abernathy 1 8 - inch pellets, and a casein-based diet contained ng/g feed quantities of testosterone, 11-ketotestosterone, androstenedione, progesterone, 17α-hydroxy-20β-dihydroprogesterone, 17β-estradiol, and thyroxine. Biomoist starter #2 contained the largest quantities of steroids, followed by Abernathy and then the casein-based diet. Oregon Moist Pellets ( 3 32 and 1 8 - inch ) also contained ng/g feed quantities of thyroxine. From first exogenous feeding, coho salmon ( Oncorhynchus kisutch) were placed on either the “high” steroid diet (Biomoist) or the “low” steroid diet (casein-based). Although concentrations of sex steroids were significantly higher in fish fed the Biomoist diet than in those fed the casein-based diet, we saw no effect of diet on sex ratios of the fish or on histology of the developing gonads. Sex steroids appeared not to be present in quantities sufficient to affect sexual differentiation.