Gateways to alien invasions in the European seas

The spatial pattern of initial introductions of marine alien species in the European Seas (including the entire Mediterranean) was investigated. Marked geographic patterns depending on the pathway of introduction were revealed, with specific countries acting as gateways to alien invasions. France and Italy were the countries mostly responsible for introductions by aquaculture, while Lessepsian species were first reported (as anticipated) in the countries of the Levantine Sea, especially Israel. Shipping was the most important pathway of introduction, with a widely dispersed geographic pattern of initial introductions, especially near large ports. Certain taxonomic groups were mostly introduced by specific pathways, and hence the taxonomic identity of the introduced alien species in each region was greatly dependent on the dominant maritime activities/interventions and the related pathways of introduction. Our data can be very useful for informing and supporting national policy and management decisions necessary to prevent future introductions of marine alien species.