The Mediterranean Sea is home to over 2/3 of the world’s charter boat traffic and hosts an estimated 1.5 million recreational boats. Studies elsewhere have demonstrated marinas as important hubs for the stepping-stone transfer of non-indigenous species (NIS), but these unique anthropogenic, and typically artificial habitats have largely gone overlooked in the Mediterranean as sources of NIS hot-spots. From April 2015 to November 2016, 34 marinas were sampled across the following Mediterranean countries: Spain, France, Italy, Malta, Greece, Turkey and Cyprus to investigate the NIS presence and richness in the specialized hard substrate material of these marina habitats. All macroinvertebrate taxa were collected and identified. Additionally, fouling samples were collected from approximately 600 boat-hulls from 25 of these marinas to determine if boats host diverse NIS not present in the marina. Here, we present data revealing that Mediterranean marinas indeed act as major hubs for the transfer of marine NIS, and we also provide evidence that recreational boats act as effective vectors of spread. From this wide-ranging geographical study, we report here numerous new NIS records at the basin, subregional, country and locality level. At the basin level, we report three NIS new to the Mediterranean Sea (Achelia sawayai sensu lato, Aorides longimerus, Cymodoce aff. fuscina), and the re-appearance of two NIS previously known but currently considered extinct in the Mediterranean (Bemlos leptocheirus, Saccostrea glomerata). We also compellingly update the distributions of many NIS in the Mediterranean Sea showing some recent spreading; we provide details for 11 new subregional records for NIS (Watersipora arcuata, Hydroides brachyacantha sensu lato and Saccostrea glomerata now present in the Western Mediterranean; Symplegma brakenhielmi, Stenothoe georgiana, Spirobranchus tertaceros sensu lato, Dendostrea folium sensu lato and Parasmittina egyptiaca now present in the Central Mediterranean, and W. arcuata, Bemlos leptocheirus and Dyspanopeus sayi in the Eastern Mediterranean). We also report 51 new NIS country records from recreational marinas: 12 for Malta, 10 for Cyprus, nine for Greece, six for Spain and France, five for Turkey and three for Italy, representing 32 species. Finally, we report 20 new NIS records (representing 17 species) found on recreational boat-hulls (mobile habitats), not yet found in the same marina, or in most cases, even the country. For each new NIS record, their native origin and global and Mediterranean distributions are provided, along with details of the new record. Additionally, taxonomic characters used for identification and photos of the specimens are also provided. These new NIS records should now be added to the relevant NIS databases compiled by several entities. Records of uncertain identity are also discussed, to assess the probability of valid non-indigenous status.

The role of commercial harbours as sink and source habitats for non-indigenous species (NIS) and the role of recreational boating for their secondary spread were investigated by analysing the fouling community of five Italian harbours and five marinas in the western Mediterranean Sea. It was first hypothesised that NIS assemblages in the recreational marinas were subsets of those occurring in commercial harbours. However, the data did not consistently support this hypothesis: the NIS pools of some marinas significantly diverged from harbours even belonging to the same coastal stretches, including NIS occurring only in marinas. This study confirms harbours as hotspots for marine NIS, but also reveals that numbers of NIS in some marinas is higher than expected, suggesting that recreational vessels effectively facilitate NIS spread. It is recommended that this vector of NIS introduction is taken into account in the future planning of sustainable development of maritime tourism in Europe.

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this bryozoan species was abundant in the La Grande Motte marina on the south coast of France. Several thousand colonies were estimated to be present within this marina attached to the floating pontoon units that supported a floating boardwalk. Of the berthed craft examined, 31% were fouled with this species, and it was occasionally a prominent fouling species. Several macroinvertebrate species were associated with A. verticillata colonies, including some NIS, Para cerceis sculpta, Paranthura japonica and Caprella scaura, that are recorded for the first time from the Mediterranean coast of France. A. verticillata might support their transfer elsewhere by providing a habitat and substrate when attached to vessel hulls.Keywords: introduced species; fouling organisms; associated species; ship hulls; shipping; marinas; pontoons.Los puertos deportivos como centros para la difusión del briozoo pseudoindígeno Amathia verticillata (Delle Chiaje, 1822) y sus asociados Resumen: El briozoo espagueti Amathia verticillata, anteriormente conocido como Zoobotryon verticillatum, fue descrito por primera vez en 1822 en Nápoles, Italia, aunque esta especie ya estaba presente en 1807 en Cádiz, España. Este ctenostomado ha sido considerado por mucho tiempo como una especie nativa del Mar Mediterráneo, pero se ha sugerido recientemente que es originario del Caribe. Es probable que haya sido introducido incrustado en los cascos de los barcos. Esta especie pseudoindígena, es decir, una especie introducida que ha sido percibida como nativa, se ha encontrado en varios puertos comerciales y deportivos del Mar Mediterráneo. En noviembre de 2014, esta especie de briozoo era abundante en el puerto deportivo de La Grande Motte en la costa sur de Francia. Se estimaron varios miles de colonias presentes en este puerto, adhe ridas a las unidades de pontones flotantes que sostienen el paseo marítimo flotante. El treinta y uno por ciento de los barcos atracados, examinados en el puerto deportivo, estaban incrustados con esta especie, cuyo aspecto algunas veces fue una sola incrustación prominente. Varias especies de macroinvertebrados se asociaron con las colonias del A. verticillata, incluyendo algunas especies introducidas que se registran por primera vez en la costa Mediterránea de Francia: Paracerceis sculpta, Paranthura japonica y Caprella scaura. Este briozoo podría ayudar a la transferencia de diferentes macroinvertebrados a otros lugares, pues proporciona un hábitat y un substrato cuando está adherido a los cascos de los barcos.Palabras clave: especies introducidas; organismos incrustantes; especies asociadas; casco del barco; navegación; puertos deportivos; pontones.

1. Despite the Mediterranean being both a hotspot for recreational boating and for non-indigenous species (NIS), no data currently exists on the recreational boating sector's contribution to the spread of NIS in this Sea.2. To improve the basis for management decisions, a wide-scale sampling study on the biofouling communities of recreational vessels and marinas was undertaken.Specifically, we surveyed over 600 boat owners and sampled the same boat hulls for NIS in 25 marinas across the Mediterranean, from France to Cyprus, to determine which factors (i.e. boat characteristics, travel behaviour, home marina) are associated with higher NIS richness on boat hulls.3. Among the surveyed boats, we found recreational vessels to travel considerably, averaging 67 travel days and 7.5 visited marinas per annum. This results in a high potential for spreading NIS, especially as 71% of sampled vessels host at least one (and up to 11) NIS. Boats with high NIS richness strongly correlate with home marinas with high NIS richness. Over half of the vessels were carriers of NIS whichwere not yet present in the marinas they were visiting. The presence of biofouling in niche areas of the hull (i.e. in the cavities and metallic parts) emerges as the best predictor for NIS richness on boats, along with longer times since their last cleaning and antifouling applications. Interestingly, colonization of NIS occurred rapidly, even on boats that had recently had their hulls cleaned professionally. Synthesis and applications.We demonstrate that recreational boating has a very high capacity for the spread of non-indigenous species (NIS) in the Mediterranean, due to both high NIS richness on boats and extensive travel. To counteract the spread of NIS, routine monitoring for new NIS needs to be established for both marinas and vessels, along with frequent pontoon cleaning. Additionally, policy should require preliminary screenings for incoming vessels from new countries, especially those emanating from high-risk marinas. The niche areas of the boat hulls should be checked first for biofouling, which was the best predictor for NIS richness since they often go overlooked with in-water cleanings are rarely have antifouling applied to them. K E Y W O R D S biofouling, connectivity, marinas, Mediterranean Sea, non-indigenous species, recreational boats, Suez Canal, vector | 2621 Journal of Applied Ecology ULMAN et AL. S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section at the end of the article. How to cite this article: Ulman A, Ferrario J, Forcada A, et al. Alien species spreading via biofouling on recreational vessels in the Mediterranean Sea.