Dynamics of helminth fauna of the digestive tract of Perca fluviatilis (Actinopterygii: Perciformes) and its relationship with zooplankton in the Samarskaya Luka National Park (Russia)

Abstract

In the present paper we studied the helminth fauna of the digestive tract of Perca fluviatilis (Perciformes) of the water bodies in the Samarskaya Luka National Park (Russia) in 1990–2016. In the early 1990s, nine species of intestinal helminths were registered for P. fluviatilis. Life cycles of 78% of them were associated with zooplankton organisms. We found correlations between fish invasion by certain helminth species and the abundance of zooplankton organisms. By 2012–2016, the proportion of parasites associated with zooplankton has decreased to 67%. Of helminths found in P. fluviatilis in 1990–1992, seven species are known there nowadays. Since 1996, we identified 12 new parasites, including two alien species. We found a double change of dominant species in the 1990s. Recently, a new factor has been added to the historical set of factors. It is the introduction, naturalisation and inclusion of alien hydrobiont species into both trophic chains of fish communities and parasitic systems of the studied water bodies. The helminth fauna of P. fluviatilis adequately reflects both features of host's ecology and changes occurring in water bodies during the last 30 years. We identified the tendencies of structural-functional ecosystem restructuring caused by both alien species introduction and, associated, changes in trophic chains of fishes with it. We predict changes in the strategy of fish behaviour, an increase in abundance and more active participation of invasive species (fish, freshwater molluscs, parasites) in trophic chains of water bodies in the Samarskaya Luka National Park connected with the reservoir, and, finally, expanding the range of consumers / hosts of alien parasites.

Keywords

• alien species
• cladocera
• copepoda
• parasites on fishes
• water ecosystem transformation