The occurrence of the protected swan mussel Anodonta cygnea (Linnaeus, 1758) and the invasive alien Chinese mussel Sinanodonta woodiana (Lea, 1834) in the fish ponds in the Wisłok River Basin (SE Poland).

The occurrence of the Chinese mussel Sinanodonta woodiana (Lea) was discovered in June and July 2011 in a fish pond located about 15 km north-west of Rzeszow (Subcarpathian region). Thirty six specimens (6 dead and 30 live) of the species were found. The Chinese mussel was absent in two other fish ponds in the same area, however the swan mussel Anodonta cygnea (L.) was found in these ponds (80 individuals: 45 dead and 35 live). At the time when the survey was conducted the ponds had already been drained for 3 to 8 months, so both populations will probably disappear from the locality. Nevertheless the new finding of the Chinese mussel in fish ponds confirms the possibility of occurrence of the species also in the waters with natural thermal regime.