Metazoic parasites of Siberian roach Rutilus rutilus lacustris (Pallas) in the Tobol river

The article describes the problems of the Ob-Irtysh basin (the Tyumen region), which is a natural focus of opisthorchosis. Localized in the bile ducts of the liver, the pathogen of opisthorchosis poses a risk to the human body. Parasitic community of Siberian roach inhabiting the Tobol Riverwas studied in the autumn period of its life cycle. There were examined 24 fish species of different sexes at the age of 0+ to 4+. There was registered the roach invasion by 9 species of para-sites belonging to 6 systematic groups: Monogenea - 2, Cestoda - 1, Trematoda - 4, Nematoda - 1, Bivalvia - 1, Copepoda - 1. Parasitization of gills by monogeny Dactylogyrus crucifer with inva-sive extensiveness of 83.3% and Paradiplozoon homoion homoion with invasive extensiveness of 16.7% has been stated. Diplostomum chromatophorum parasitizes in the lens of the eye, in total 18 of the examined fish are invaded. Opisthorchis felineus was found in muscles with invasive exten-siveness of 29.2%. Immature specimens of Sphaerostoma bramae were found in the intestines of nine fish examined. Mesentery of 4 fish species and liver of 1fish species examined are affected by Raphidascaris acus at a larval stage. The dominant parasite in the study is Rhipidocotyle campanula. Trematode at the metacercaria stage was found on the gills and fins, the overall infection rate comes to 70.8%. Also, Ergasilus sieboldi parasitizes on the gills and fins of the examined roach species. Depletion of the species composition of parasites is observed in the autumn period of the roach life cycle.