1st Record: Woclawy/Poland/Wista-Vistula River (1931, Grabowski et al. 2004). Polish populations are not self-sustaining. Genetic studies indicate that Polish populations are derived from those breeding in the Elbe River and other North Sea tributaries (Czerniejewski et al. 2012).
Poland-Baltic states/Central Baltic (Panning 1939; Herborg et al. 2003); Woclawy/Poland/Wista-Vistula River (1931, Grabowski et al. 2004; Jablonska-Barna et al. 2013); Hango/Finland/Gulf of Finland-Baltic Sea (2004, Ojaveer et al. 2004); Lithuania/Baltic Sea and Curonian Lagoon (1935, Bacevicius and Gasiunaite 2008, increasing catches, several gravid females)