Species diversity of helminths of the digestive system of the bream and roach of the Saratov Reservoir

The data on helminths of the digestive system of the bream Abramis brama Linnaeus, 1758 and the common roach Rutilus rutilus Linnaeus, 1758 (Osteichthyes, Cyprinidae) from the middle part of the Saratov reservoir (Koltsovo-Mordovinskaya floodplain) are given. In 2013-2016, 40 specimens of A. brama and 47 specimens of R. rutilus were studied by standard parasitological methods. Bream has 8 species of worms of different systematic groups, including Cestoda - 2, Trematoda - 1, Chromadorea - 3, Acanthocephala - 2. The community of intestinal and liver parasites of roach includes 5 species: Cestoda - 1, Aspidogastrea - 1, Chromadorea - 2, Acanthocephala - 1. The degree of invasion of fish by helminths circulating through food webs is low. The bream is dominated by the carp-specific nematode Rhabdochona denudata (Dujardin, 1845) Railliet, 1916 (Spirurida, Rhabdochonidae) (invasion intensity 27.5 %, invasion intensity 1-126 ind., abundance index 5.8 ind.). No dominant parasites were found in the common roach, three species (Contracaecum microcephalum (Rudolphi, 1819), Aspidogaster limacoides Diesing, 1835 and Raphidascaris acus (Bloch, 1779)) have the status of subdominants. During the research period, there were significant fluctuations in the qualitative and quantitative indicators of fish invasion (species composition of parasites, their occurrence and average number), which is determined by the feeding characteristics of bream and roach in each specific year.