First record of the brackish water dreissenid bivalve Mytilopsis leucophaeata in the northern Baltic Sea

Conrad’s false mussel, Mytilopsis leucophaeata has been found in the central Gulf of Finland, which is the first record of this brackish water dreissenid species in the northern Baltic Sea. In 2003 a strong recruitment of young dreissenid bivalves was observed and in 2004 dense assemblages consisting of adult M. leucophaeata were discovered in an area affected by cooling water discharges from a nuclear power plant. The introduction of the species has obviously taken place via ballast water transport, resulting in a successful establishment in a favourable warm water environment. Based on the wide salinity tolerance, M. leucophaeata might also colonize areas inhabited by functionally similar bivalves if able to survive the cold winter conditions.