Introductions of fish and crabs in the Schelde estuary

Since 1991, we have systematically recorded the fish and crab fauna of the Schelde estuary in samples of power plants cooling water and of fyke nets. In this period, we found 71 species of which eight were introduced (table 1). Additionally, one native and three non indigenous crab speices were observed. All non native marine species recorded in the estuary arrived from North America. Probably, their presence is due to transport via the ballast water of ships docking at the port of Antwerp. All non native freshwater species in the estuary arrived from eastern Europe and Asia. The occurrence of these species in the estuary is almost invariably due to deliberate introductions. The most recent observations of non-indigenous species in the Schelde estuary date from October 2001 when two young Vimba vimba and an adult Micropogonias undulatus were caught nearby the Dutch-Belgian border (Stevens et al., submitted). These species have not been recorded yet in Belgium