EN
Seasonal changes in prevalence and mean intensity of several parasite species representing four systematic classes, and occurring in four herbivorous fish (common, grass, silver and big head carp) in pond culture were analysed. Frequency of metacercariae of Diplostomum sp. appeared not to be dependent on the season of the year. The seasonal occurrence patterns of two cestode species, Khawia sinensis and Bothrio-cephalus acheilognathi, are described with regard to the process of recruitment of larvae by fish, their maturation and removal of old specimens from fish. Two species of Crustacea (Ergasilus sieboldi and Argulus foliaceus) and two species of Hirudinea (Piscicola geometra and P. pojmanskae) appeared to be most frequent on fish in autumn.