Alien species in the marine and brackish ecosystem: the situation in Belgian waters

In total 61 aquatic alien species (AAS) are known from Belgian marine and brackish waters, eight of which are considered as cryptogenic species. The majority of the Belgian AAS have established self-sustaining populations, although for some species the establishment is uncertain or in need of verification. Prime introduction vectors are shipping, including small recreational craft, and aquaculture. Most AAS originate from the temperate northwest Pacific. The invasion rate has been increasing during the last two decades.