Recreational boating as a major vector of spread for alien species around the Mediterranean

Marinas are biologically diverse hotspots often constructed out of artificial materials that act as moving island habitats in contrast to neighboring natural habitats. This research presents the results of a wide investigation on the importance of recreational boating as a major vector of spread of alien species around marinas in the Mediterranean. To begin, marinas were chosen based on: frequency of non-resident visiting recreational boat traffic, number of berths, permissions and feasibility. Over 2015 and 2016, 34 marinas were assessed for their presence of alien species from 7 countries (Spain, France, Italy, Malta, Greece, Cyprus and Turkey), representing a west- to east gradient. In 25 of the examined marinas, random surveys were completed with approximately 25 recreational boat captains to determine boat history of travel and hull maintenance and techniques, and then fouling biota were collected from the boat hulls and later identified in the laboratory to species level. Firstly, the marinas of highest risk will be illustrated using the number of alien species present combined with the realized marina connectivity of recreational boaters, and then the similarities between various marinas are compared. Select marinas in the eastern Mediterranean were found to contain the highest amount of alien species (30+) due to the higher number of Indo-Pacific species in the eastern Mediterranean from the proximity of the Suez Canal as the major gateway of invasion in the Mediterranean. Next, several abiotic factors were tested to determine which ones favor alien species settlement and survival in marinas. Thirdly, an analysis of alien species found on the boat hulls will be presented for resident vs. visiting recreational vessels to illustrate how recreational boating is a major vector of spread in comparison to other vectors such as ballast water. This work required many taxonomic expertises (from Europe to Australia) to competently complete the species identification portion of the work. The main taxonomic groups found both in the marinas and on the vessels, as part of the fouling communities, were ascidians, bryozoans, crustaceans, molluscs and polychaetes.