|Exotic molluscs in the Mediterranean Basin: current status and perspectives|
Gofas, S.; Zenetos, A. (2003). Exotic molluscs in the Mediterranean Basin: current status and perspectives. Oceanogr. Mar. Biol. Ann. Rev. 41: 237-277
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
Anthropogenic factors; Aquaculture; Ballast; Introduced species; Shipping; Species diversity; Anadara inaequivalvis (Bruguière, 1789) [WoRMS]; Brachidontes pharaonis (P. Fischer, 1870) [WoRMS]; Bursatella leachi [sic] [WoRMS]; Cerithium scabridum Philippi, 1848 [WoRMS]; Musculista senhousia (Benson, 1842) [WoRMS]; Pinctada radiata (Leach, 1814) [WoRMS]; Rapana venosa (Valenciennes, 1846) [WoRMS]; Rhinoclavis kochi (Philippi, 1848) [WoRMS]; Strombus persicus Swainson, 1821 [WoRMS]; Xenostrobus securis (Lamarck, 1819) [WoRMS]; Mediterranean Region [Marine Regions]; Marine
An updated synthesis is presented for the records of introduced Mollusca in the Mediterranean basin. The rationale for taking molluscan records as significant is discussed. The Mediterranean Sea, with some 1800 native species of Mollusca, currently houses 139 exotic species, of which 85 form established populations, 52 are aliens recorded once or twice, and two are questionable. Ten species (the gastropods Cerithium scabridum, Rhinoclavis kochi, Strombus persicus and Bursatella leachi and the bivalves Pinctada radiata and Brachidontes pharaonis in the eastern Mediterranean, the gastropod Rapana venosa and the bivalves Anadara inaequivalvis, Musculista senhousia, and Xenostrobus securis in the northern Adriatic and the western Mediterranean lagoons) are locally invasive. The bulk of the introduced species (118 species, of which 70 are established, 46 aliens, and two questionable) are species of lndo-Pacific origin found mainly in the eastern basin of the Mediterranean. Among these species, some which live in the Suez Canal are most likely to have spread by their own means through this waterway (these are the "lessepsian immigrants" in the most restricted sense). For other species, the intervention of transport by ship hulls or ballast water can be suspected. Only two of these lndo-Pacific immigrants are found, very locally, in the western Mediterranean. The process of immigration has become unprecedented in magnitude since the 1970s and is not slowing down. The remaining introductions of marine species are connected with mariculture and/or shipping. These vectors account for the occurrence or dissemination of only 29 exotic species in the Mediterranean basin, but four of these are invasive. The data regarding the Mollusca do not support any substantial faunal change caused by an influx of subtropical faunal elements through the Straits of Gibraltar. Some local species boundaries may have changed slightly in the past decades but not a single newcomer to the Mediterranean basin by this route could be detected in this survey. The open sea localities of the western Mediterranean remain virtually free of immigrant mollusc species. The areas most severely affected by the occurrence of exotic species (eastern Mediterranean, Adriatic and lagoons in the western Mediterranean) are those where the species richness of the native fauna is low. It is speculated that this low diversity is a crucial contribution to the success of the newcomers. In the affected areas, the impact on the local fauna is considerable in terms of species composition of the assemblages but so far no native Mediterranean species can be reported as endangered as an effect of a biological invasion.