Geographic Variability in Morphological Traits of Lower Amur Grayling Thymallus tugarinae (Salmonidae: Thymallinae)

The analysis results for morphological variability in the Lower Amur grayling Thymallus tugarinae, one of the five species of grayling fish (Thymallinae) inhabiting the Amur River basin has been reported. Overall, 16 samples of juvenile specimens of the same size class, collected in different parts of the habitat area, are analyzed. A discriminant analysis revealed high-level morphological speciation in grayling fish from different rivers, based on the classification accuracy comprising, on average, 96%. The hiatus in a range of morphological traits was revealed, when comparing certain samples. Clustering classified the grayling fish into groups considered morphologically different because of the variable habitat conditions. The fish from the rivers of the Amur River estuary area were well differed from each other by the morphotype, despite the similarity of the rivers conformed to the same comparatively small region. The graylings inhabiting different sections of a large river were more morphologically distinct, than the fish of small rivers isolated from each other. In addition, increases or shift in the limits of variations of the values of the morphological diagnostic traits of the species were revealed.