Long-Term Influence of Surfagon Injection on the Cytological Condition of the Gonads and Level of Thyroid and Sexual Steroid Hormones in Young Brown Trout Salmo trutta

Abstract

The long-term effect of the injection of a synthetic analogue of gonadotropin releasing hormone—Surfagon—on the reproductive system of juvenile brown trout Salmo trutta has been studied. The concentration of thyroid hormones in the blood, the rate of gametogenesis, and physiological adaptation of individuals to external conditions increased over five months after injection. The changes identified predetermine the formation of a predominantly resident fish of the brown trout population. Based on the patterns found, the interrelation of the hormonal status, puberty, and the formation of life strategies in salmon species has been analyzed.