Diversity of the parasite fauna of cyprinid (Cyprinidae) and percid (Percidae) fishes in the Vistula Lagoon, Poland.

A total of 2398 fish specimens (1091 Percidae and 1307 Cyprinidae) belonging to 16 species (3 Percidae and 13 Cyprinidae), caught in the Polish part of the Vistula Lagoon were examined within December 1994-March 1997. The parasites found were identified as belonging to 63 taxa (61 species as well as Diplostomum spp. flukes and glochidia Unionidae gen. sp. which could not be identified to species) of the Microsporea (1), Protozoa (1), Myxozoa (2), Monogenea (10), Digenea (15), Cestoda (11), Nematoda (11), Acanthocephala (5), Hirudinea (1), Mollusca (1), Copepoda (4), and Branchiura (1). The percids and cyprinids were found to support 37 and 40 parasitic taxa, respectively, the taxon-richest parasite fauna occurring in zander, Sander lucioperca (26 taxa), followed by carp bream, Abramis brama (24), European perch, Perca fluviatilis (24), roach, Rutilus rutilus (19), ruffe, Gymnocephalus cernuus (15), and Prussian carp, Carassius gibelio (11). The remaining fish species hosted less than 10 parasitic species each. Metacercariae of the genus Diplostomumn, found in about 37% of the fish examined, and Tylodelphys clavata, recorded in about 24% of the fish, proved the commonest parasites. The study showed the Vistula Lagoon cyprinid and percid parasite fauna to be dominated by freshwater species, frequencies of their occurrence in the brackishwater lagoon being lower than those in freshwater reservoirs. Frequencies of the 6 marine parasitic species found in the lagoon were, too, lower than those in the sea. It is suggested that some of the parasites (Ancyrocephalus paradoxus, Diplozoon paradoxum of the Monogenea, Diplostomum spp., Tylodelphys clavata of the Digenea, and Achtheres percarum of the Copepoda) prefer brackishwater habitats.