Condition of Sex Glands in the Young of the Current Year of Rainbow Trout Subjected to Surfagon Injections

Condition of sex glands and thyroid and steroid hormone levels in the blood are assessed in the young of the current year of rainbow trout cultivated in the high-mountain area of South Vietnam and subjected to injections of surfagon (synthetic analogue of gonadotropin-releasing hormone). In the conditions of the trout hatchery (Vietnam), gonads of the young of the current year are characterized by substantial anomalies, including an appearance (in addition to females and males) of hermaphrodite and sterile individuals. A single injection of surfagon 1 month after hatching leads to stabilization of the development of sex glands and decrease of the proportion of sterile individuals (from 41 to 22%). This study is the first attempt of the assessment of the effect of the injection of gonadotropin-releasing hormone analogue on the development of sex glands in the early ontogeny of fishes.