The marine aliens phenomenon

Abstract

Many eyebrows were raised when EU Commissioner for the Environment, Maritime Affairs and Fisheries Karmenu Vella recently raised the issue of invasive alien species during one of his speeches. The term ‘alien species’ is no longer challenging for many, but is the phenomenon of the introduction of such species so bad? Of the estimated 1,000 marine non-indigenous species (also known as exotic, alien, non-native or allochthonous species) recorded to date in the Mediterranean, more than half are considered to be established or spreading. Among them, the highest number are crustaceans, followed by molluscs and fish. The entry point for almost 500 of the newcomers is the Suez Canal so they are called ‘Lessepsian’ migrants. Ferdinand de Lesseps was the French diplomat who steered through plans to build the canal in the 19th century. The other 500 come from warm regions of the eastern Atlantic, and are thus expanding their native range by moving into the Mediterranean through the Straits of Gibraltar.