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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.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.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 which were 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. [ABSTRACT FROM AUTHOR]

The Suez Canal is the main pathway of introduction of non-indigenous species into the Mediterranean Sea. The successive enlargements of the Suez Canal have raised concern over increasing propagule pressure resulting in continuous introductions of new non-indigenous species and associated degradation and loss of native populations, habitats and ecosystem services. The United Nations Environment Programme (UNEP) through its Barcelona Convention has pledged to protect the biological resources, habitats and ecosystem services of the Mediterranean Sea, and have committed to spatial protection measures. Yet, UNEP shied away from discussing, let alone managing, the influx of tropical non-indigenous biota introduced through the Suez Canal. Surveys, funded by the Regional Activity Centre for Specially Protected Areas (UNEP RAC/SPA), established by the Contracting Parties to the Barcelona Convention, revealed that marine protected areas in the eastern Mediterranean have been inundated by these non-indigenous species, and may in fact function as hubs for their secondary dispersal. We call attention to the failure of an environmental policy that left the entire Mediterranean Sea prone to colonization by highly impacting non-indigenous species, including poisonous and venomous ones. Scientific research has been documenting this bioinvasion for over a century, yet beyond the ambit of marine scientists there is a lack of awareness of the scale of Mediterranean-wide consequences and scant appetite to enact the necessary environmental policies. [ABSTRACT FROM AUTHOR]

Analyses of marine alien species based on national/regional datasets are of paramount importance for the success of regulation on the prevention and management of invasive alien species. Yet in the extant data systems the criteria for the inclusion of records are seldom explicit, and frequently inconsistent in their definitions, spatial and temporal frames and comprehensiveness. Agreed-upon uniform guiding principles, based on solid and transparent scientific criteria, are therefore required in order to provide policy makers with validated and comparable data. Following a meta-analysis on the records of marine alien species in the Mediterranean Sea, we recommend a judicious approach to compiling the data. Here, three categories of uncertainty were identified: species' taxonomic identification, species' actual occurrence in the area, and its status as an alien. In proposing guiding principles to standardize such datasets, we aim to encourage discourse on logical, standardized and transparent criteria to substantiate records of alien species. [ABSTRACT FROM AUTHOR]

The transport of organisms across oceans is an anthropogenic agent of global change that has profoundly affected the natural distribution of littoral biota and altered the makeup of biogeographic regions. The homogenization of marine biotas is a phenomenon especially affecting coastal regions and is spearheaded by a suite of opportunistic species at the expense of native species. Climate change may exacerbate the trend: sea surface temperatures, hydrodynamics, pH and carbonate cycles, already show marked fluctuations compared to the past. Alien invasive species are impacted by the change of marine climate in a variety of ways, which are we have just begun to notice, observe and interpret. A conceptual framework has yet to be conceived that links theories on biological introductions and invasions with the physical aspects of global change. Therefore predicting the scale of invasions or their impact on biodiversity is a daunting task. Integration of biological and environmental information systems, niche models, and climate projections would improve management of aquatic ecosystems under the dual threats of biotic invasions and climate change. The recorded spread of alien species and analysis of patterns of invasions may serve as the starting point for searching connections with climate change descriptors. The Mediterranean Sea is home to an exceptionally large number of alien species, resulting from its exceptional history and multiple vectors. For much of the twentieth century alien thermophilic species, which had entered the Mediterranean through the Suez Canal, have been confined to the Levantine Basin. In recent years climate driven hydrographic changes have coincided with a pronounced expansion of alien thermophilic biota to the central and western basins of the Mediterranean. We discuss some changes in emergent functions and services in Mediterranean ecosystems under the combined effect of invasive species and climate changes. [ABSTRACT FROM AUTHOR]

At 726 the number of recorded multicellular non indigenous species (NIS) in the Mediterranean Sea is far higher than in other European Seas. Of these, 614 have established populations in the sea. 384 are considered Erythraean NIS, the balance are mostly ship and culture-introductions. In order to effectively implement EU Regulation on the prevention and management of the introduction and spread of invasive NIS and the Marine Strategy Framework Directive in the Mediterranean Sea it is crucial that this priority pathway is appropriately managed. Three potential impediments – incomplete and inaccurate data; unknown impacts; policy mismatch – hinder implementation. Current geographical, taxonomical and impact data gaps will be reduced only by instituting harmonized standards and methodologies for monitoring NIS populations in all countries bordering the Mediterranean Sea, prioritizing bridgehead sites and dispersal hubs. The option of implementing European environmental policies concerning marine NIS in member states alone may seem expedient, but piecemeal protection is futile. Since only 9 of the 23 states bordering the Mediterranean are EU member states, the crucial element for an effective strategy for slowing the influx of NIS is policy coordination with the Regional Sea Convention (Barcelona Convention) to ensure consistency in legal rules, standards and institutional structures to address all major vectors/pathways. [ABSTRACT FROM AUTHOR]