Distribution and Biological Features of Grayling Thymallus thymallus (Thymallidae) in the European North-East of Russia

— The distribution and some ecological features of the European grayling Thymallus thymallus are studied in the extreme European Northeast of Russia. In many water systems of the region the state of the species is close to natural one. A significant ecological and genetic diversity of the populations is found. According to the ratio of genotype frequencies of the polymorphic two allelic system of blood serum transferrins the grayling populations in the Pechora River system can be combined into two clusters, Ural and Timan ones which differ from the groupings of the Kola Peninsula. It is suggested that a wide spectrum of ecological conditions provides a successful existence of all species diversity of European grayling in the northeast of the European part of Russia.