Aquatic Invasions (2007) Volume 2, Issue 3: 243-257 Open Access doi: http://dx.doi.org/10.3391/ai.2007.2.3.9 © 2007 The Author(s). Journal compilation © 2007 REABIC Research Article Alien species in the marine and brackish ecosystem: the situation in Belgian waters Francis Kerckhof 1, Jan Haelters1 and Stephan Gollasch2 1Management Unit of the North Sea Mathematical Models (MUMM), Royal Belgian Institute of Natural Sciences, 3e en 23e Linieregimentsplein, 8400 Oostende, Belgium 2GoConsult, Grosse Brunnenstr. 61, 22763 Hamburg, Germany E-mail:
[email protected] (FK),
[email protected] (SG) Received: 15 August 2007 / Accepted: 9 September 2007 Abstract 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. Key words: Belgium, aquatic species introductions, shipping, aquaculture Introduction some recognized cryptogenics. In our list we opted for a rather conservative approach, i.e. we Worldwide, many species have successfully did not attempt to prepare an exhaustive list of colonised new habitats as an ongoing all species of non-native origin that have ever phenomenon. Coastal waters are heavily exposed been recorded in Belgian marine waters, whether to introductions of alien species as a result of the established or not.