High occurrence of non-indigenous species on recreational boat hulls in the Mediterranean Sea

A large-scale analysis of fouling assemblages from 367 recreational boat hulls was carried out in 2015-2016 in 20 Mediterranean marinas from France, Italy, Malta, Greece and Turkey. A total of 155 species, including native, cryptogenic and non-indigenous species (NIS), were identified. On the average, 2.5±1.9 NIS were collected from boat hulls, and only 12% of the inspected boats were not carrying any NIS. The maximum number of NIS per single boat was observed in Licata, Sicily (10 NIS). The average percentage of NIS over the total number of species ranged from 11.2% (in Sainte-Maxime, France) to 42.3% (in Ostia Lido, Italy). These results testify that recreational boats travelling across the Mediterranean Sea do carry different invertebrate species on their hulls, including several NIS. The role of recreational boating in the introduction and spread of NIS should urgently be incorporated into regulations aiming to manage this vector responsible of NIS introduction both at the Mediterranean and European levels.