EN
A total of 233 perch, Perca fluviatilis L. specimens caught within April 1995?June 1997 at two sites in the Gulf of Gdansk were examined. The fish were found to host flukes (metacercariae of Tylodelphys clavata, Diplostomum spp. and adult Bunodera luciopercae), cestodes (plerocerkoids of Eubothrium crassum and Triaenophorus nodulosus, and adult Proteocephalus percae), nematodes (Camallanus lacustris, C. truncatus, Hysterothylacium aduncum L3 and adult), and acanthocephalans (Acanthocephalus lucii, A. clavula). Most prevalent were A. lucii (33.9%) and T. clavata (28.8%). Most of the parasites were found in the perch caught off the Vistula mouth and the level of infection was higher there than elsewhere in the Gulf, which indicates that ecological and hydrological conditions in the area enhance parasitism.