Characteristics of the parasite fauna of brown trout (Salmo trutta morpha lacustris L.) in lakes of Karelia

Brown trout (S. trutta L.) occurs widely in northern Europe coastal waters from Cheshskaya Bay in the north to the Black Sea in the south. The paper relates the results of studies on the parasite fauna of brown trout (S. trutta morpha fario) and lake trout (S. trutta morpha lacustris) in Lake Ladoga, Lake Onega and Lake Pyaozero. Comparative analysis of the parasite faunas in these lakes was carried out, specific parasite species were identified, the most common species were distinguished. Infection intensity and prevalence were determined, distinctions between the parasite faunas were specified. Relying on published and original data, a complete list of parasites currently observed in trout from the lakes in question was compiled, the parasite fauna now comprising 42 species. The parasite species composition was found to be highly diverse. The typological likeness of lakes Ladoga and Onego, and the high similarity of their faunas by no means imply that they are identical. The parasite fauna of trout in Lake Ladoga includes generalist species pertinent to boreal plains. Generally speaking, the highest similarity is demonstrated by the trout parasite faunas of lakes Ladoga and Onego. They have near identical sets of dominant parasite species. The only exception was the acanthocephalan Corynosoma semerme found in trout from Ladoga. This fact indicates that the fish are related not only taxonomically, but also ecologically.