Finding of the Invasive Amphipod Gmelinoides fasciatus (Stebbing, 1899) in Watercourses of the Lake Onega Basin

The invasive amphipod Gmelinoides fasciatus (Stebbing, 1899) was not previously recorded in the rivers of the Lake Onega basin, although it has spread widely in its littoral in recent years. In 2019 and 2020, this species was found to inhabit the estuarine zones of watercourses (the Rybreka River and the Drugaya River) at a considerable distance from the lacustrine littoral zone (0.5 and 1.7 km, respectively). It was revealed that G. fasciatus is included in the communities of both pools and riffles and in some areas reaches dominant positions in the macrozoobenthos, which indicates the possibility of further expansion of its range owing to the river ecosystems of the region.