Distribution of the Mass Species of Benthic Crustaceans on the Nearshore Slope of Lake Ladoga.

The species composition and distribution of crustaceans in the nearshore zone of Valaam Island (Ladoga Lake) have been investigated by a syringe sampler, a dredge, and video recording. Five species of crustaceans, Asellus aquaticus (Linnaeus, 1758), Monoporeia affinis (Lindström, 1855), Pallaseopsis quadrispinosa (G.O. Sars, 1867), Mysis relicta Lovén, 1862 and Gmelinoides fasciatus (Stebbing, 1899); have been recorded at a depth of 1–25 m. The vertical distribution of naturalized Baikal amphipods G. fasciatus is described and features of their coexistence with native species are characterized. The distribution of the alien species depends significantly on wave intensity, types of sediments, and depth range. The distribution of the most numerous native species, P. quadrispinosa, is influenced by the depth range. The types of sediments do not affect the quantity of all native crustaceans in the nearshore zone. The local species successfully compete with G. fasciatus in all conditions. All these species inhabiting the littoral zone are more resistant to wave action when compared with alien species. Therefore, the open littoral zones serve as natural refugees that preserve the diversity of indigenous species. The data on the spatial distribution of crustaceans make it possible to characterize the benthic communities in the poorly studied parts of the littoral and sublittoral zones and, as a result, the food base of bentophagous fishes. [ABSTRACT FROM AUTHOR]