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Abstract

Distribution of Ponto-Caspian amphipod Pontogammarus robustoides in Latvian waters.

Abstract

Data of the monitoring of inland waters, conducted during 1999-2005, showed that the alien Ponto-Caspian amphipod Pontogammarus robustoides is quite widespread in Latvia. The species was detected at 15 monitoring sites. This non-indigenous amphipod occurs in the lower reaches and mouths of rivers emptying into the Baltic Sea, water reservoirs located on the Daugava River, and nearshore lakes which are connected to the brackish waters of the sea. The spread of P. robustoides in the lower reaches of the Daugava River and its water reservoirs must have originated from the intentional introduction of this amphipod into the Keguma Water Reservoir in the 1960s. Meanwhile, the invasion of this amphipod into the lower reaches of other Latvian rivers and nearshore lakes, including the vicinities of the Baltic Sea ports Ventspils and Liepaja, proceeded from areas already invaded by P. robustoides by migrating through the Baltic Sea waters, probably in hull fouling of ships. The closest source populations, which might have contributed to the dispersal of this aquatic invader, inhabited the Curonian Lagoon and the mouth of the Daugava River.