In the Baltic Sea, the great sandeel (Hyperoplus lanceolatus), a common fish species that inhabits sandy substrates, is an important element in the diet of marine mammals, sea birds, and piscivorous fish. It can also act as a transmitter of parasites to its predators, but parasitological studies on this species are limited. We sampled great sandeels in April 2016 in two areas of the southern Baltic Sea (SB-south of Bornholm and GG-the Gulf of Gdansk) and found parasitic anisakid nematodes in both locations. The only one species of nematode parasites has been detected: liver worm (Contracaecum osculatum) with average prevalence of infection 8.96%. This is the first study to report on infection of H. lanceolatus with anisakid nematodes in the southern Baltic Sea and our results suggest that the great sandeel may play a role in the transmission of liver worm in the food web of this marine environment.
Keywords: Contracaecum osculatum; Great sandeel; Southern Baltic Sea.