Co-occurrence of Sinanodonta woodiana with native Unionidae in the lower Oder

The Asiatic bivalve Sinanodonta woodiana (Lea, 1834), which is more and more widespread in all parts of Europe, in Poland has been mostly reported from lentic waters, especially fish ponds. In contrast to some other European countries, no data have been published on its presence in rivers of Poland. In 2015, monitoring was carried out in the lower Oder River and in the mouth of the Warta River, as a result of which S. woodiana was recorded there for the first time. This was possible due to prolonged drought, which led to extremely low water levels in most of the inland water bodies and watercourses, so that other research methods could be used. The presented results confirm that the species spreads easily by colonizing waters of various types, which in the future may lead to the formation of large populations.