Freshwater mussels (Mollusca, Bivalvia, Unionidae) of the Danube river basin of Ukraine

Abstract

Despite the ongoing environmental problems, the basin of the Danube river is the least disturbed on the territory of Ukraine. Thus, its malacofauna is a nominal standard for the southern water systems of Central Europe. Particular attention is paid to freshwater mussels, which are indicator species and most of which are subject to special protection. During 2009-2011, 50 points of the Danube river basin were surveyed. In 23 of them, seven species of Unionidae were recorded: U. pictorum, U. tumidus, U. crassus s. lato, A. anatina, A. cygnea, P. сomplanatа and S. woodiana, which is an invasive species. The index of occurrence of freshwater mussels in general was 100% in the Lower Danube river (5 study areas), 42% in Tisa river (31 study areas), 33.3% in Seret river (3 study areas), 36% in Prut river (11 study areas). The index of occurrence of species was rather low: 24% of A. anatina, 22% of U. tumidus, 22% of U. crassus, 16% of U. pictorum, 14% of P. complanata, 14% of S. woodiana, and 2% of A. cygnea. U. crassus was not found in the Lower Danube river, while A. cygnea was found only there outside the main watercourse. The invasive species S. woodiana occurred in the Lower Danube river and in the sub-basin of Tisa river (with 83% and 20% frequency, respectively. The mean values of population densities ranged from 1.00 (A. cygnea) to 6.14 ind./m2 (S. woodiana), and the mean biomass varied from 1.14 (P. сomplanatа) to 797.54 g/m2 (S. woodiana). In general, the composition of aboriginal malacofauna was stable, with a tendency to decreasing population densities

Keywords

• unionidae
• danube river basin
• species composition
• frequency of occurrence
• population density
• biomass