Identifying the top issues of marine invasive alien species in Europe

Stemming from a recent freshwater invasives conference, Caffrey et al. (2014) identified 'the top 20 issues' that relate to invasive alien species (IAS) management in Europe.With a view to complement and balance the issues highlighted in their account, we offer six important additions that relate to the marine environment.These are: preventive measures, concerns of loss of taxonomic expertise and species identity, gaps in the knowledge of certain taxa and regions, inconsistencies of terminology, need for validation of data and the importance of concentrating on pathways, and their vectors, and levels of certainty associated with these routes.