First record of Pontogammarus robustoides Sars, 1894 (Crustacea: Amphipoda) in the Gulf of Riga (Baltic Sea).
The paper presents the first record of the Ponto-Caspian amphipod crustacean Pontogammarus robustoides G.O. Sars, 1894, in the Gulf of Riga, Baltic Sea. Eight individuals of this invasive amphipod were found in June 2009, in shallow waters of the gulf near Yurmala city. Most likely this species entered the Gulf of Riga from Latvian rivers emptying into the Baltic Sea, where it was previously found. However, introduction via ships coming from either southern or north-eastern parts of the Baltic Sea is also a possibility.