Status of the invasive brackish water bivalve Mytilopsis leucophaeata (Conrad, 1831) (Dreissenidae) in the Ponto-Caspian region

Since 1996, the invasive Conrad's false mussel Mytilopsis leucophaeata (Conrad) has been recorded in brackish water bodies in the Ponto-Caspian region, which includes the basins of the Black Sea, Azov Sea, and Caspian Sea. In the Azov-Black Sea basin, where the number of records is increasing, its range currently includes the Dniester, Dnieper-Southern Bug, and Don River estuarine systems, and the mouth of the Tuapse River near the town of Tuapse. In the Caspian Sea basin, M. leucophaeata is present in areas near the mouths of the Volga and Ural rivers, and in the south Caspian Sea, near Bandar Anzali town. The present study analyses new records from this region as well as previously published records. All sites in the Azov-Black Sea basin with records of living specimens of M. leucophaeata were characterized by changes in the hydrological regime due to the effect of hydraulic engineering (mostly along deep-water shipping canals or for fish ladders). The most probable vector for long-distance dispersal of M. leucophaeata is transatlantic shipping to the Black Sea basin; while for secondary spread, coastal and inland shipping across adjacent ports is likely. Introduction of this species to the Caspian Sea could have resulted from specimens first present in the Black Sea or from independent long-distance transfer.