We investigated the growth of hydromycoflora on the eggs of sea trout (Salmo trutta morpha trutta L.) in river water of different eutrophication levels. The eggs investigated were collected from 42 females caught during their spawning migration in the Parsęta River (west Pomerania), in Świbno on the Vistula River, and from those bred in fresh water in hatcheries at Miastko. The water for the experiments was collected from three different rivers: Biała (most), Krasna (middle) and Supraśl (low eutrophication). Fifty-three species of fungi were identified on the eggs of forty-two females of sea trout. Achlya polyandra, Saprolegnia ferax and Saprolegnia parasitica were found on the eggs of all females. In the water from the Biała we observed 25 zoosporic fungus species on eggs, 34 in water from the Krasna, and 43 in water from the Supraśl.
Forty zoosporic fungus species were found on the eggs of females from Świbno and 34 from Miastko, while only 25 were observed on the eggs of females from Parsęta. The following rare fungi were found: Achlya inflata, Aphanomyces frigidophilus and Saprolegnia salmonis.