Vistula – the biggest river in the Baltic basin

Dikerogammarus villosus (Sowinsky, 1894) has been recorded for the first time in the Vistula River, the biggest river in Poland and in the whole Baltic drainage system. Until now the species has been found in the Bug River that is a tributary of the Vistula. It has migrated there from the Ponto-Caspian basin through the central invasion corridor (namely Pripet-Bug canal). Another population of that species has been found in the Oder River. It came there via the Mittelland Canal from the Rhine River that had been colonised from the Black Sea basin through the southern invasion corridor. In the Vistula River, D. villosus co-occurs only with other Ponto-Caspian gammarids