Scientists believe that biological diversity can be best preserved nowadays in wilderness reserves that are practically in natural state. The goal of our project was to study two small lakes, Verkhniy Neris and Nizhniy Neris, connected by a channel and located in northwestern Karelia (30°E and 66°N). They are situated in the Holarctic region, the Circumpolar subregion, the Arctic Sea province, the European district, the White Sea basin and the forest-tundra zone (Berg, 1949). Flowing out of Lake Nizhniy Neris is the Siltajoki River, which empties into the Olanga River. The lakes cover an area of less than 1.0 km² and are up to 15 m deep.
Four fish species live in the lakes: Coregonus lavaretus pidschian (Gmelin), Salvelinus alpinus (L.), Salmo trutta L., Phoxinus phoxinus (L.). The fish fauna of the lakes incorporates a postglacial community of Salmonidae which is seldom encountered not only in Karelia but also in Northwest Europe (Ferguson, 1986). Water bodies inhabited by this fish community are located predominantly in the mountain tundra of Scandinavia and the Kola Peninsula. As the community is easy to destroy, it should be carefully protected.