Next step of invasion: the Asian clam Corbicula fluminea (O. F. Müller, 1774) (Bivalvia: Cyrenidae) colonises smaller sandy rivers in Poland

This contribution presents a new observation of Corbicula fluminea (O. F. Müller) in Poland, found in 2021 in the Nida River, 40 km north of the nearest known locations. No species of the genus Corbicula has been previously recorded in the Nida, continuously explored for freshwater mussels since 2019. Live specimens were found in 20% of the collected sediment samples. The presence of young clams suggests that the population may be expanding rapidly through active movement or passive downstream drift. The clam was most likely introduced to the Nida by anglers as bait, but other possible pathways (e.g. transfer by kayaks or waterfowl, releases by aquarists) and the species’ impact on invaded ecosystems and native bivalves are discussed.