Helminths of three species of White Sea fishes.

Parasitic fauna of the White Sea cod, Gadus morhua marisalbi; the navaga, Eleginus nawaga; and the shorthorn sculpin, Myoxocephalus scorpius, in the White Sea was repeatedly studied, but no large-scale parasitological surveys have been made in the recent three decades. To fill this gap, we conducted a survey of the helminths of these three fish species at the White Sea Biological Station (Karelia, Russia) of the Lomonosov Moscow State University in August 2021. The navaga (50 specimens studied) was found to be infected with 13 species of helminths; the White Sea cod (50 specimens), with 12 species; and the shorthorn sculpin (21 specimens), with 13 species. Plerocercoids of Diphyllobothrium schistochilus and third-stage juveniles of Pseudoterranova bulbosa were recorded in the White Sea for the first time. The helminth infracommunities of the navaga and the White Sea cod were closer in structure to each other than to those of the shorthorn sculpin. In general, the levels of helminth infection of the White Sea cod, the navaga, and shorthorn sculpin have been consistently high over 85 years of observations in the White Sea, but long-term trends in the abundance of some helminth species were multidirectional.