Abstract

The authors investigated the growth of hydromycobiota on the eggs of rainbow trout (Oncorhynchus mykiss) in waters of different trophicity. Of the O. mykiss eggs that were investigated, 16.6% were found to be infected by mycotal species. Thirty mycotal species were found on eggs obtained from adult female representatives. Achlya polyandra, A. radiosa, Aphanomyces laevis, Leptomitus lacteus, Saprolegnia ferax and Saprolegnia parasitica belonged to the species that were most commonly encountered. Aphanomyces frigidophilus, Candida albicans and Zoopage phanera were rarely found in salmonid fishes. Amino acid, carbohydrate and urease tests were used, and all analyses of species from the Achlya, Aphanomyces, Leptolegnia, Pythium and Saprolegnia genera showed that they assimilate glucose and starch. However, they did not assimilate glycine, leucine, lysine, ornithine, and arabinose. Urease was assimilated only by species from the Leptolegnia, Pythium and Saprolegnia genera.

Key words: Oncorhynchus mykiss, rainbow trout, eggs, mycotal species, infection, hydrochemistry.