EN
Eighty individuals of migratory brown trout (Salmo trutta trutta) from the River Słupia (Central Pomerania) during spawning were studied. The liver, muscles, and heart from 13 healthy males and 26 healthy females (control group) as well as from 23 males and 18 females with ulcerative dermal necrosis (UDN; study group) were collected directly after catch of the fish. Our investigations showed that UDN coincides with the functioning of antioxidative system defences. The pathophysiological mechanism of UDN impact is connected with a decrease in the most important antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) and total antioxidant activity of muscles, liver, and heart. Increases in oxidative stress markers and intensity of lipid peroxidation level caused by UDN are suggested.