Changes in the distribution of amphipods in the Daugava River, Latvia

Scientific information on amphipods and other peracaridan crustaceans in Latvian inland waters is insufficient. Therefore investigations of these animals are indispensable, especially because of the ongoing biological invasions of Ponto-Caspian amphipods causing changes in macroinvertebrate assemblages. Our recent investigation revealed that the alien amphipod Gammarus varsoviensis dominates amphipods in the upper courses of the Daugava River, whereas the other alien amphipod Pontogammarus robustoides prevails in the lower reaches of the river. Both these Ponto-Caspian amphipods were found co-occurring with the indigenous Gammarus pulex in the middle course of the Daugava River upstream from the Pļaviņas Reservoir. We predict that in the future the indigenous G. pulex will be fully exterminated by alien amphipods in the Latvian part of the Daugava River.