EN
In 127 specimens of grayling Thymallus thymallus (LINNAEUS, 1758) originating from three rivers: Łeba, Reda and Radunia and caught between 1992 and 1994, 8694 parasite individuals (apart from Protozoa) were found, belonging to 11 species (including one genus determined). Among them Trichodina sp., Ichtyophthirius multifiliis, Plagioporus stefanskii were first ever revealed in grayling. In Poland it has turn out to be a new host for the following parasites: Trichodina sp., Ichthyophthirius multifiliis, Diplostomum spathaceum, Crepidostomum metoecus, Plagioporus stefanskii, Cucullanus truttae, Pomphorhynchus laevis. Other species, previously noted in Polish graylings, were also found: Cyathocephalus truncatus, Cystidicoloides ephemeridarum, Echinorhynchus truttae, Echinorchynhus borealis. The differentiated parasitofauna of the grayling in Łeba, Reda and Radunia points to the fish isolation in particular biotopes. It also revealed an increased number of parasite species in fish from Radunia occurring due to the operation of Salmon-like Fishes Culture Centre in Rutki near Gdańsk.