Aquatic molluscs of the Zemplínská šírava dam reservoir (East Slovakia)

Abstract

The mollusc communities of the Zemplínská Šírava dam reservoir were studied in 2019. The reservoir, built in 1961–1965, is situated in the eastern part of Slovakia near the boundary with Ukraine; with its area of 33 km2 it is the second biggest dam reservoir in Slovakia. Nineteen species (13 gastropods, 6 bivalves) were recorded in the first more detailed inventory of its malacofauna. The mollusc communities in individual sites consisted of 8–14 species. The existence of littoral zone overgrown by macrophytes is important especially for populations of pulmonate snails while unionids were usually found on muddy or sandy bottom. Five non-native species were recorded. The abundant population of non-native D. polymorpha probably has a negative impact on unionids because of the shortage of suitable substrata (rocks, stones) for attachment, and as a result D. polymorpha uses shells of dead or live unionids.