Phenotypic diversity and growth rate of bream Abramis brama (Linnaeus, 1758) in the north-eastern part of the native range

This paper described the main phenotypic characteristics - morphological diversity and growth rate of bream from the Pechora River, which is the extreme north-eastern border of the native range of this species. The area of its distribution in the territory of the European northeast of Russia is shown. It was revealed that the most optimal bream habitats in the Pechora River basin are the subordinate system - numerous ducts and non-cutoff bayou lakes of the lower stream of the river. It was assumed that their favorable temperature regime and well-developed food supply contribute to this, which is confirmed by the analysis of size and weight characteristics of bream. It was shown that there are no statistically significant differences in the average values of meristic parameters of bream samples from the channels of the Pechora and Vychegda rivers. The level of intra-population morphological diversity, established using the Zhivotovsky µ index, also indicates the phenotypic similarity of the studied groups. The stable phenotypic (genotypic) structure of this species was assumed to be the main reason for the low variability. Perhaps an equally important factor is the short isolation time of the studied bream populations.