Invasive species <i>Dreissena polymorpha</i> in the Northern Dvina River estuary

The features of distribution of Dreissena polymorpha (Pallas, 1771) in the northeastern part of the range and in the estuary part of the Northern Dvina River are described. Based on the earlier studies of different authors, it was suggested that the population of this mollusk is independent and self-replicating. To prove that, our study provides some population characteristics of D. polymorpha settlements. Mollusk samples were taken in the summer in 2018-2021. The research was conducted in the upper delta and in the lower part of the estuary section in order to evaluate the agglomeration. In total, 1538 individuals were selected from three sites of collection. A set of morphometric measurements was performed. Intra-population diversity was studied, weight and length of D. polymorpha individuals were evaluated. Statistically significant differences were found between the individuals living in the upstream estuary and those living in the Northern Dvina River delta, which is explained by the differences caused by of abiotic factors such as current velocities, availability of suitable substrates, amount of nutrients. There were no significant differences in the presented parameters between the second and third sampling site, due to the relative proximity of the sampling stations. The importance of further study of the biology and ecology of this mollusk in the North Dvina River basin is shown.