Ecological aspects of the formation of the helminth fauna of Perca fluviatilis (Actinopterygii: Perciformes) of the Usinsky Bay (Kuibyshev Reservoir, Russia)

Abstract

The fauna of the multicellular parasites of European perch Perca fluviatilis (Peciformes) of the Usinsky Bay of the Kuibyshev Reservoir was studied in 2019–2020; nine taxa of helminths were found. The parasite prevalence of most of the intestinal helminth species, associated with the zooplankton community, did not exceed 12–25%. In the fish with a body length of 117–200 mm, fish juveniles and benthos organisms played a significant role in the parasite transmission. The Usinsky Bay was a buffer zone at the margin of the “river-reservoir” system and had a specific hydrological regime. This promoted favorable conditions for the spreading of alien species of aquatic organisms in the ecosystem of the reservoir; in some cases this led to an increase in the invasion of indigenous fish (European perch) by invader parasites. As a result of this process, the invasive species of trematode Apophallus muehlingi became dominant in the helminth fauna of the European perch. High degree of infestation of European perch by this parasite indicated wide distribution of its first intermediate host, the alien mollusk Lithoglyphus naticoides, in the Usinsky Bay. Other species of parasites, associated with this invader, were not found in Perca fluviatilis. Helminths of the European perch can be used as biological markers to identify migratory activity, the vector of the invasion of some alien species, the range of their hosts, the population abundance, and indirect infection by alien hosts in different water bodies of the Volga River basin.