摘要：Dikerogammarus villosus is a pontogammarid species that has rapidly extended its range in Europe starting from the Ponto-Caspian basin. In the 1990s it moved from the Hungarian to Austrian section of the River Danube, and then (after the opening of the Main-Danube canal) invaded German inland waterways. Using the canals joining the different river systems, the species has reached the River Odra. There it quickly spread both up- and downstream, reaching for the first time the Baltic Sea coastal waters (the Szczecin Lagoon) by 2002, extending the list of alien species that can be found in the Baltic. Based on samples taken in 2002-2004, D. villosus occurrence in the Szczecin Lagoon and adjacent coastal waters were identified. A mass occurrence of the species was found in some places already in 2002. Owing to the fact that an important (both for open sea and inland traffic) shipping route crosses the lagoon, populated by the new species, it is very probable that the area can act as a stepping stone in dispersal of D. villosus to other oligohaline Baltic Sea coastal waters.
