Fish parasite fauna of the middle reaches of the Lena river and its tributaries under growing man-caused impact

On the middle course of the Lena river there is a large extent of infection of fish with parasites with a complex development cycle. Infection of the pike with plerocercoids of Diphyllobothrium latum is caused by contamination with communal sewage. In the parasitofauna of the fish of the Vilyui river, an increase in the simplest gill trichodinis observed, which is associated with the eutrophication of the reservoir. The fish of the Aldan river showed a greater extent of invasion by myxosporidia than in fish from the middle reaches of the Lena river. The focus of diphyllobothriosis in the middle reaches of the Lena river is facilitated by the contamination of the reservoir with municipal waste from urban sewers and discharges of river vessels during navigation. In general, the epizootic situation in reservoirs, subject to anthropogenic impact, and adjacent territories is not entirely satisfactory. It may be improved with the decreased contamination of the external environment and hence the increased resistance of the fish organism.