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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]

Abstract: Since the 1960''s, the Pacific oyster Crassostrea gigas has been introduced for mariculture at several locations within NW Europe. The oyster established itself everywhere and expanded rapidly throughout the receiving ecosystems, forming extensive and dense reef structures. It became clear that the Pacific oyster induced major changes in NW European estuaries. This paper reviews the causes of the Pacific oyster''s remarkably successful establishment and spread in The Netherlands and neighbouring countries, and includes a comprehensive review of consequences for the receiving communities. Ecosystem engineering by C. gigas and a relative lack of natural enemies in receiving ecosystems are identified as the most important characteristics facilitating the invader''s successful establishment and expansion. The Pacific oyster''s large filtration capacity and eco-engineering characteristics induced many changes in receiving ecosystems. Different estuaries are affected differently; in the Dutch Oosterschelde estuary expanding stocks saturate the carrying capacity whereas in the Wadden Sea no such problems exist. In general, the Pacific oyster seems to fit well within continental NW European estuarine ecosystems and there is no evidence that the invader outcompetes native bivalves. C. gigas induces changes in plankton composition, habitat heterogeneity and biodiversity, carrying capacity, food webs and parasite life cycles. The case of the Pacific oyster in NW European estuaries is only one example in an increasing series of biological invasions mediated by human activities. This case-study will contribute to further elucidating general mechanisms in marine invasions; invasions that sometimes appear a threat, but can also contribute to ecological complexity. [Copyright &y& Elsevier]

Aim Limnomysis benedeni Czerniavsky, 1882 is a mysid crustacean native to the Ponto-Caspian (Black and Caspian Sea) rivers and estuaries, and has recently spread across Europe through intentional and unintentional introductions. We explored the structuring of genetic variation in native and non-native populations with an aim to trace the sources of the invasions, and to infer whether the spread has occurred through a single or multiple invasion waves. Location Native estuaries in the Ponto-Caspian basin (Volga, Don, Dnieper, Dniester, Danube) and the recently colonized range along the Danube–Rhine river systems and Lithuania. Methods A fragment of the mitochondrial COI gene was sequenced to assess genetic affinities and diversity in native and recently established populations. Results The genetic diversity in the native regions is organized into several strongly diverged haplotype groups or lineages, partly allopatric, partly sympatric. All these lineages have also spread beyond the native range. Even the recent rapid dispersal across Europe along the Danube–Rhine system towards the North Sea basin involved several lineages from the Danube delta sector. The structuring of genetic diversity among invaded sites suggests multiple invasion events to the Danube–Rhine drainage. This contrasts with data from some other Ponto-Caspian species, where a single haplotype seems to have occupied most invaded areas. There is no evidence that intentionally stocked reservoirs in the Baltic Sea basin would have contributed to further unintentional spread of L. benedeni. Main conclusions Limnomysis benedeni is spreading across Europe using the southern invasion corridor. The invasion most likely involved several waves from differentiated sources in the native Danube delta area. [ABSTRACT FROM AUTHOR]

Over the past century, the potential for aquatic species to expand their ranges in Europe has been enhanced both as a result of the construction of new canals and because of increased international trade. A complex network of inland waterways now connects some previously isolated catchments in southern (Caspian, Azov, Black, Mediterranean seas) and northern (Baltic, North, Wadden, White seas) Europe, and these waterways act as corridors for nonnative species invasions. We have developed a conceptual risk assessment model for invasive alien species introductions via European inland waterways, with specific protocols that focus on the development of environmental indicators within the socioeconomic context of the driving forces-pressures-state-impact-response framework. The risk assessment protocols and water quality indicators on alien species were tested for selected ecosystems within 3 main European invasion corridors, and these can be recommended for application as part of the Common Implementation Strategy of the European Commission Water Framework Directive, which aims to provide a holistic risk-based management of European river basins. The conceptual structure of the online Risk Assessment Toolkit for aquatic invasive alien species is provided and includes 3 main interlinked components: online risk assessment protocols, an early warning system, and an information transmitter for risk communication to end users. [ABSTRACT FROM AUTHOR]

Species invasion is one of the leading mechanisms of global environmental change, particularly in freshwater ecosystems. We used the Food and Agriculture Organization's Database of Invasive Aquatic Species to study invasion rates and to analyze invasion pathways within Europe. Of the 123 aquatic species introduced into six contrasting European countries, the average percentage established is 63%, well above the 5%–20% suggested by Williamson's "tens" rule. The introduction and establishment transitions are independent of each other, and species that became widely established did so because their introduction was attempted in many countries, not because of a better establishment capability. The most frequently introduced aquatic species in Europe are freshwater fishes. We describe clear introduction pathways of aquatic species into Europe and three types of country are observed: "recipient and donor" (large, midlatitude European countries, such as France, the United Kingdom, and Germany, that give and receive the most introductions), "recipient" (most countries, but particularly southern countries, which give few species but receive many), and "neither recipient nor donor" (only two countries). A path analysis showed that the numbers of species given and received are mediated by the size (area) of the country and population density, but not gross domestic product per capita. [ABSTRACT FROM AUTHOR]

The European green crab, Carcinus maenas, has a native distribution that extends from Norway to Mauritania. It has attracted attention because of its recent invasions of Australia, Tasmania, South Africa, Japan and both coasts of North America. To examine the population structure of this global invader in its native range, we analysed a 502-base-pair fragment of the mitochondrial cytochrome c oxidase I (COI) gene from 217 crabs collected in the North Atlantic and 13 specimens from the Mediterranean. A clear genetic break (11% sequence divergence) occurs between the Mediterranean and Atlantic, supporting the species-level status of these two forms. Populations in the Faeroe Islands and Iceland were genetically distinct from continental populations (FST = 0.264–0.678), with Iceland represented by a single lineage also found in the Faeroes. This break is consistent with a deep-water barrier to dispersal in green crabs. Although there are relatively high levels of gene flow along the Atlantic coast of Europe, slight population structure was found between the central North Sea and populations to the south. Analysis of variance, multidimensional scaling, and the distribution of private haplotypes support this break, located between Bremerhaven, Germany, and Hoek van Holland. Similar biogeographical and genetic associations for other species, such as benthic algae and freshwater eels, suggest that the marine fauna of Europe may be generally subdivided into the areas of Mediterranean, western Europe and northern Europe. [ABSTRACT FROM AUTHOR]

The Chinese mitten crab, Eriocheir sinensis (H. Milne Edwards), is an invasive species that lives as an adult predominantly in freshwater but migrates seawards to breed. It has spread via ballast water and/or intentional introduction to Continental Europe, Southern France, U.S.A. (San Francisco Bay) and the United Kingdom. Analysis of detailed historic data from the outbreak in Europe was digitised and analysed using Geographical Information Software. This revealed that there were two separate invasions in Northern Europe and Southern France, with an average range expansion during the peak period of 562 km/year from 1928–1938 (Northern Europe) and 380 km/year from 1954–1960 in Southern France. Size class distribution data from the lower estuary of the River Elbe (Germany) (1932–1936) illustrate migration patterns to and from the estuary over the year. Marking experiments determined that the mean rate of downstream migration for adults was 11.5 km/day (SD 3.54; n=7), up to a maximum of 18.1 km/day. The carapace width of upstream-migrating animals increased by 3 mm/100 km. The peak period for upstream migration was March to July, followed by the downstream season from July to September. This data set, extracted from historic references, represents one of the most complete pictures of the life cycle and spreading behaviour of this alien invader. [ABSTRACT FROM AUTHOR]

Accidental escapees from aquacultural facilities are an ongoing problem facing scientists, conservationists, policy makers and naturalists throughout the world. The topmouth gudgeonPseudorasbora parva, a small cyprinid native to Southeast Asia, was introduced to Romanian waters in 1960viathe aquaculture trade and has since spread throughout Europe. It first appeared in England in an ornamental fish farm near Romsey in Hampshire. The aim of the present study was to quantify the dispersal of this potentially highly invasive species from an ornamental fish farm into the wild. In order to measure the dispersal of escapees, intensive electrofishing surveys were carried out between June and September 2003 in the catchment downstream of the fish farm. The distribution of topmouth gudgeon in the catchment was found to be limited and patchy. The presence of small individuals suggests that the species has successfully established itself in the wild, but this remains to be confirmed. The results were examined in light of invasion theory principles of biological resistance and ecological fitness. [ABSTRACT FROM AUTHOR]