Risk screening of the potential invasiveness of non-native marine crustacean decapods and barnacles in the Mediterranean Sea

Non-native marine crustaceans can exert detrimental impacts on native marine communities by altering habitat and ecosystem function. The Mediterranean Sea is particularly vulnerable to introductions of non-native crustaceans, as evidenced by their remarkably high establishment success. In this study, 20 species of non-native marine crustacean decapods and barnacles of which eleven extant and nine ‘horizon’ were screened for their potential invasiveness in the Mediterranean Sea. Using the Aquatic Species Invasiveness Screening Kit and including an additional nine native species to increase accuracy, calibrated risk thresholds of 3.5 for the BRA (Basic Risk Assessment) and 8.5 for the BRA + CCA (BRA + Climate Change Assessment) were obtained that distinguished reliably between invasive and non-invasive species. All 20 non-native species were classified as carrying a high risk of invasiveness for the Mediterranean Sea, both for the BRA and the BRA + CCA. Chinese mitten crab Eriocheir sinensis was by far the highest risk species, followed by Harris mud crab Rhithropanopeus harrisii, Asian shore crab Hemigrapsus sanguineus, bay barnacle, Amphibalanus improvisus, and lesser swimming crab Charybdis (Goniohellenus) longicollis. The findings of this study will provide management and control directions for non-native marine crustaceans in the Mediterranean Sea, with special emphasis on regulations regarding ballast waters, which represent one of the main introduction pathways for these aquatic organisms.