Zoogeographic changes in the composition of the ichthyofauna of large rivers in northern European Russia have been clarified. A characteristic feature of the studied region is a significant number of fish species of the cold-water complex: Salmoninae, Coregoninae, Thymallinae and Osmeridae. The proportion of different fish groups in the ichthyofauna of the river basins changes significantly in the direction from west to east. The proportion of Salmoniformes, representatives of the cold–water complex, increases, while that of Cypriniformes decreases. The number of families from other orders, represented by a much smaller number of species, remains almost unchanged. The Pechora River basin is transboundary, and the interpenetration of the European and Asian ichthyofauna occurs through it. According to the degree of faunal similarity, the basins of the Onega, Northern Divina and Mezen rivers are closer to the Western zoogeographic subdistrict with a predominance of fish of the Baltic complex; Volonga, Pechora and Kara are closer to the Eastern subcircle with a predominance of fish of the Siberian complex. According to the degree of faunal similarity, the basins of the Onega, Northern Divina and Mezen rivers are closer to the Western zoogeographic subdistrict with a predominance of fish of the Baltic complex; the basins of the Volonga, Pechora and Kara rivers are closer to the Eastern subdistrict with a predominance of fish of the Siberian complex. The conditional boundary between the two groups runs along the basin of the Volonga River, in which the proportions of European and Siberian species are the same. In the zoogeographic zoning of the territory of the north of northern European Russia, it is proposed to subdivide the Eastern subdistrict into Severodvinsk and Pechora areas, with Severodvinsk and Mezen subareas in the first, and Pechora and Kara subareas in the second.
A.P. Novoselov (Wed,) studied this question.