Helminth Fauna of the Great Cormorant Phalacrocorax carbo in Lake Ladoga, Northwestern Russia

New data on the species composition of parasites of the great cormorant Phalacrocorax carbo from the shores of Lake Ladoga are presented. The parasitic fauna of the great cormorant consists of nine species. Four species have been found in the northwestern part of Russia for the first time: the trematode Metorchis xanthosomus and nematodes Cyathostoma microspiculum, Syncuaria squamata, and Eustrongylides mergorum. P. phalacrocoracis, Syncuaria squamata, and Cyathostoma microspiculum are parasites specific to cormorants. Other parasites identified (Contracaecum rudolphii, Petasiger radiatus, P. phalacrocoracis, Paradilepis scolecina, and Ligula intestinalis) are typical and widespread helminths of fish-eating birds that are ubiquitous in the Palearctic. Some species (M. xanthosomus, E. mergorum, C. rudolphii, and L. intestinalis) are of epizootic importance.