Distribution and current status of non-indigenous mollusc species in Lithuanian inland waters

We present a comprehensive overview of distribution data of non-indigenous mollusc species in Lithuanian inland waters. The data are based on our own observations obtained during 2007-2013 as well as on published and unpublished records from the last 80 years. Four non-indigenous species have been reported to occur in Lithuanian freshwaters: Dreissena polymorpha, Lithoglyphus naticoides, Potamopyrgus antipodarum and Physella acuta. The last species, however, has not been found in Lithuania since the 1950s. D. polymorpha is the most widespread non-indigenous mollusc species in Lithuania. It was observed in 159 out of 226 investigated localities. The other species are less common. L. naticoides was recorded in 43 sites, whereas P. antipodarum was found in 35 localities. In addition to the possible reappearance of P. acuta, four more mollusc species which are currently absent from Lithuanian freshwaters have been reported as non-indigenous from neighbouring countries and thus might potentially invade Lithuanian inland waters in the future.