Distribution and recent status of freshwater mussels of family Unionidae (Bivalvia) in the Czech Republic

This study is devoted mainly to the distribution and its changes, inhabited and preferable habitats of bivalves from family Unionidae in the territory of the Czech Republic and the discussion of major threats and conservation measures. Altogether 6 autochthonous (Unio crassus, Unio pictorum, Unio tumidus, Anodonta anatina, Anodonta cygnea, Pseudanodonta complanata) and 1 allochthonous species (Sinanodonta woodiana) has been known in the Czech Republic. All these species occurred in all three river basins (Labe, Odra, Danube) and watersheds (North, Baltic and Black seas). A. anatina is the most widespread and common unionid while P. complanata is an autochthonous bivalve with the most restricted area of distribution. U. crassus has been a significantly disappearing species. As in most European countries, pollution and habitat loss including fragmentation and degradation, together with other factors such as water abstraction, invasive species and loss of fish hosts are the main threats affecting their populations.