[Diurnal dynamics of thyroid and sex steroid hormones in the blood of yearlings of the resident form of Black Sea trout Salmo trutta labrax].

Abstract

The diurnal dynamics of the content of thyroid and sex steroid hormones is investigated in the blood of the resident form of Black Sea trout in summer. The maximums and minimums of concentration of the investigated hormones do not coincide over 24 h, except for the decrease in the level of T3 and testosterone before dawn. The dynamics of the investigated hormones is controlled to a high extent by the sex of fish in the morning and in the daytime.