SEASONAL-CHANGES IN FISH BIOMARKERS

Seasonal changes in the detoxification, hormone levels, energy metabol ism and water content were measured injuvenile 2-year-old brown trout held in two environmentally different test conditions. In spite of the different test conditions, the course of seasonal changes in the meas ured biomarkers was quite similar in both test group fish. However, th e measured values of these biomarkers differed significantly between t he groups, and also between sexes. Although the fish were juveniles, s easonal changes similar to adults were observed in male gonadal growth and plasma testosterone concentration. Also, only in males, during th e spawning period, the liver ethoxyresorufin-O-deethylase activity was negatively correlated with the plasma testosterone concentration, whi ch was at its highest at that time. The Liver detoxification activity reached maximum in winter. Plasma osmotic concentration was also highe r in winter than summer. During the entire year, the tissue-water cont ent of the ''laboratory'' fish was significantly higher than that of t he fish farm group. Energy resources of the fish increased during summ er, and were high in autumn and early winter. Between the groups notab le differences were observed only in winter.