The distribution and abundance of the invasive ctenophore Mnemiopsis leidyi in the Bornholm Basin, an important spawning ground of several fish stocks, and in adjacent areas in the central Baltic Sea was studied in November 2007. The study showed that M. leidyi were relatively small (body length 18.6 ± 7.6 mm) and they were patchily distributed over a large part of the investigated area. Specimens were found on 68 and 59% of stations sampled with a Bongo net (n=39) and an Isaac-Kidd midwater trawl (n=51), respectively. Vertically, the highest densities of M. leidyi occurred at 40 to 60 m around the halocline. Horizontally, the highest abundances were found north and west of Bornholm, but relatively high densities were also observed in the Slupsk Furrow. The mean abundance was 1.58 ± 2.12 ind. m^-2, the peak abundance was 8.92 ind. m^-2, and the average and peak population density were 0.03 ± 0.05 and 0.28 ind. m^-3, respectively. The abundances are low compared to densities recently observed in other areas of the Baltic region (e. g. Limfjorden, Åland Sea) and the estimated predation impact on zooplankton by M. leidyi was negligible in November 2007. However, because of the ctenophore’s wide distribution in the central Baltic Sea, its ability for rapid population growth, and its potential influence on fish stocks by competing for food and by preying on fish eggs and newly hatched larvae, close monitoring of the future development of M. leidyi in the Baltic Sea is strongly recommended.

The solitary ascidian Styela clava Herdman, 1882 is recorded for the first time in the Mediterranean region. It was found in the Bassin de Thau, near Sète; it has not yet been found in the Mediterranean Sea. The Bassin de Thau specimens are described and compared with Northern European specimens. The proximity of commercial shellfisheries to the discovered populations, and the absence of S. clava from other harbours and marinas along the coast, suggests that the species may have been introduced by shellfish transfer.

Non-indigenous marine species (NIMS) have only recently caught general interest in Denmark, and baseline studies are needed to identify what species are of particular importance in order to prioritize management and research efforts. We used large data sets compiled in monitoring databases to quantify annual nation-wide changes in abundance of non-indigenous soft-bottom invertebrates (from grab samples) and hard-bottom macroalgae (from diver based percent cover values) in Denmark. Based on criteria of being either abundant (constituting >1% of the entire Danish assemblages) or increasing in abundance, NIMS of particular interest were found to be Mya arenaria and Bonemaissonia hamifera (abundant), Crepidula fornicata, Ensis americanus, Neanthes succinea (a cryptogenic species), Marenzelleria spp. (increasing), and Sargassum muticum (abundant and increasing). In addition, new and/or warm-water eurohaline NIMS such as Gracilaria vermiculophylla and Crassostrea gigas, should be given attention as these species are expected to increase in the future. Finally, species not included in existing monitoring programs (hard-bottom estuarine invertebrates, fish, parasites, highly mobile species) should also be targeted in future sampling programs.

The brachyuran crab genus Carcinus consists of two species, C. maenas and C. aestuarii, both of which have invaded multiple regions of the globe. C. maenas has proven a particularly adept invader, establishing introduced populations on every non-polar continent outside its native range. This species has also exhibited the capacity to spread rapidly once established and has potential for significant ecological and economic impacts throughout its introduced range. The possibility of both species invading additional coastal ecosystems, and the importance of larval dispersal—both current-driven and ballast water-mediated—to the successful establishment and expansion of introduced populations, recommend the development of rapid and cost-effective tools for detecting and monitoring Carcinus larvae in environmental samples. We have developed a PCR-RFLP approach that enables the specific and highly sensitive detection of both C. maenas and C. aestuarii in mixed plankton samples, including those drawn from ballast water. Our approach successfully identifies specimens from throughout the native and introduced ranges of both species, and excludes all non-target brachyuran species tested, including a number of species whose ranges overlap with those of the Carcinus species. Sensitivity of our PCR-RFLP assay is extremely high, allowing the detection of single stage I zoea in over 1 gram (filtered weight) of mixed non-target plankton. The assay also successfully detected single larvae in mixed plankton derived from ballast water, indicating the potential utility of this approach as a tool for targeted screening of Carcinus sp. in ship’s ballast.

Recent reports of Chinese mitten crabs (Eriocheir sinensis) in the St. Lawrence River and Estuary were compiled to assess the possible sources of the species based on genetic analyses and data on shipping traffic. Between 2004 and 2007, nine specimens were captured in both the fresh and estuarine waters of the St. Lawrence; a number unprecedented in the 40 years since the mitten crab was first sighted in the Great Lakes–St. Lawrence Basin. These sightings, added to those of the eastern United States, are indicative of a large-scale wave of introduction of the mitten crab to Eastern North America. Genetic analyses have suggested that the St. Lawrence specimens likely originated in Europe. No significant changes have been noted in maritime traffic to the St. Lawrence in recent years, but analyses have revealed that 42% of ships came from European countries where established populations of Chinese mitten crab have exhibited recent bursts in abundance. It is suggested that the recent wave of introduction of mitten crabs to Eastern North America is related more to changes in the abundance of European populations than to changes in shipping vector activity. These recent sightings are of major concern with regard to the establishment and spread of the species. It is therefore recommended that long-term monitoring programs be set up immediately to track the progress of the mitten crab invasion in the St. Lawrence River basin.

The invasive Indian caprellid crustacean Caprella scaura sensu lato has been recorded for the first time in the Iberian Peninsula in July 2005 in the brackish waters of the Roses Bay (Girona, Spain). Its most probable introduction vector was shipping. Some ecological and distributional features are succinctly included.

The invasive zooxanthellate coral Oculina patagonica is recorded for the first time from Algeria (2005, 2007) and Tunisia (2006, 2008). Its occurrence in the Mediterranean is summarized and aspects of its biology are discussed in an attempt to understand how the new sites may have been colonized.

The recent findings of the red swamp crayfish, Procambarus clarkii, in groundwater-filled pits in an abandoned quarry (Hadera, central coastal plain) constitute the first record in the wild of this notoriously invasive species in Israel. Crayfish had been offered for sale in local pet shops: twenty years ago several illegally imported specimens had been confiscated by the Israel Nature and Parks Authority and two of the specimens were deposited at the National Collections, Tel Aviv University. The recent finding of a small reproducing population established in a semi natural habitat in Israel raises great concern regarding the potential widening of its range and of the limited options for its eradication.

The Ponto-Caspian amphipod Dikerogammarus villosus(Sowinski) invaded Lake Constance, Central Europe (47°39'N, 9°18'E,) in 2002 and within four years had colonized the entire littoral zone of the upper lake basin, replacing the formerly dominant species Gammarus roeseli Gervais. Fifteen fish species were sampled from six littoral sites in the upper lake basin in 2005 and 2006, and their stomach contents were compared with samples taken prior to the replacement of G. roeseli by D. villosus. Three zoobenthivorous fish species (European eel Anguilla anguilla (L.), Eurasian perch Perca fluviatilis L., and burbot Lota lota (L.)), which had regularly consumed G. roeseli, included D. villosus immediately into their diet in similar proportions. Shifts in amphipod consumption have thus not been detected, whereas effects of the invasive amphipod on the macrozoobenthos community, which on their part might affect the food base of littoral fish, require detailed study.

Dietary breadth and diet overlap were examined in two native fish species (Eurasian perch Perca fluviatilis, Balon’s ruffe Gymnocephalus baloni) and two invading species (round goby Neogobius melanostomus, bighead goby Neogobius kessleri) in the Middle Danube (Slovakia) at dawn and dusk over two consecutive 24-h periods in late summer 2004. Dietary breadth was narrow in all species/age classes except perch of ages 4 and 5. Dietary overlap between native fishes and the invading gobies was very high, except for age 3 perch. This high overlap was due to a preference, high in some cases, for gammarids. Our preliminary results suggest the potential for competition between the invading and native fishes, which requires further study.

The chub is a freshwater fish of the family Cyprinidae, which is widely distributed throughout Europe. Prior to 2001 there were no reports of chub being present in Ireland. In 2001 and again in 2004 it was reported that an angler had caught chub in a section of the River Inny. On neither occasion were live specimens retained for authentication. In 2005 a number of live, angler-caught chub from this river were formally identified. In order to determine the status of this non-native and potentially invasive fish species in this renowned Irish coarse, game and pike fishery, an electric fishing survey was conducted in 2006. Seventeen chub were captured during this operation. All were taken from one relatively short (c. 0.8 km), shallow (≤0.5 m) and moderately fast flowing section of river. The fish ranged in fork length from 15 to 41 cm and in age from III+ to X+ years old. Among the fish captured, there were two immature fish, six females and nine males. The stomach contents revealed a diet of insect, fish, plant material and detritus. A relatively fast growth rate was recorded. While relatively few chub were captured during the survey, those examined were healthy and most were in spawning condition. It is considered that the chub were introduced to the river by anglers in an effort to increase the diversity of coarse angling species available in Ireland. The potential impact of the chub on natural biodiversity and on the community composition of native and naturalised fish species in the river is discussed.

Introductions of alien species, regardless of their actual or potential impacts, can be considered as a biocontamination of the ecosystem. A simple method to assess biocontamination is described and tested on benthic macroinvertebrate communities from European inland waterways. This method includes calculations of abundance contamination and richness contamination at ordinal taxonomic rank, from which integrated estimations of biocontamination are derived. Our method can be applied to data collected during routine water quality monitoring, and allows estimation of biocontamination at specific study sites as well as integrated assessment of ecosystems or assessment units. Results clearly show that the main European inland waterways are highly biologically contaminated. They also indicate that richness contamination precedes abundance contamination, and that severe abundance contamination may be caused even by a single ecologically aggressive alien species. Comparison of biocontamination indices and ecological quality status by conventional methods suggests that these metrics are negatively correlated, and richness contamination has a stronger negative affect than abundance contamination. Biocontamination warrants inclusion within the development of holistic estimates of ecological quality status and should be considered in water management policy.

The present study reports the first occurrence of an alien spionid polychaete Polydora cornuta Bosc, 1802, in Izmit Bay, Sea of Marmara, Turkey. A dense population of P. cornuta (up to 170 ind.m^-2) found at 7 sampling stations in the bay on 18 August 2006. Our findings show that currently this alien polychaete is a key species of polluted soft bottom benthic assemblages in Izmit Bay.

Balanus amphitrite has not been recorded in the German Bight until now. However, harbour water from the East Frisian Island Norderney contained cyprids identified as B. amphitrite. Following these observations in summer 2002 the search for adult individuals in the German Bight, especially in the harbour of Norderney was enhanced with regular inspections until 2007. The consistent absence of adult individuals indicates that the cyprids are unable to settle under the environmental conditions in the German Bight. In contrast, wild cyprids settled and metamorphosed spontaneously within one day after transfer into the laboratory, where the temperature of the untreated seawater was raised from 18 to 27°C. The findings suggest that there is a threshold temperature critical for the successful recruitment of settling stages in the German Bight with the local water temperatures being currently too low.

A specimen of the Red Sea pebble crab, Ixa monodi was collected in 2005 from the Bay of Gökova, on the Aegean coast of Turkey. This species, first collected in the Mediterranean in 1955 from the Bay of Mersin, SE Turkey, is quite common off the Israeli coast. In 1999 the species was collected off Rhodes Island, Greece, and the present record provides evidence of its dispersal in the Aegean Sea.

Percnon gibbesi is reported for the first time from Libya. This plagusiid crab is the most invasive decapod species to enter the Mediterranean Sea. It was first recorded in 1999 from the Balears and Sicily and has since spread from Spain to Turkey. This is the first record from the southern rim of the Mediterranean.

The record of Boeckella triarticulata in Southern Italy attests the expanding distribution of this Australasian copepod in Europe. The species was found in 3 recently realized lakes out of 21 water bodies sampled. The young age of the lakes colonized suggests that this species establishes itself in still immature aquatic habitats with a plankton community at an early developmental stage. Drawings of the species are provided and compared to those from literature.

The invasive amphipod Pontogammarus robustoides G.O. Sars, 1894 was first recorded in Lake Ladoga in August 2006 during an expedition by the Institute of Limnology Russian Academy of Sciences to investigate the lake’s littoral zone. The species was found associated with another alien amphipod, Gmelinoides fasciatus, in a shallow littoral area of the Volkhov Bay. The biomass of the two amphipod species was 25.2% and 15%, respectively of the total macrobenthos, with 1456 and 864 mg WW m^-2. The appearance of P. robustoides in Lake Ladoga is of great concern as this new invader may alter the ecological balance in the littoral zone of the largest European lake.

A swarm of the Ponto-Caspian mysid Hemimysis anomala was found in a small boating harbour on Lough Derg, the most downstream lake on the Shannon River system, Ireland’s largest river. Some hundreds of individuals were found in an area with macrophyte growth on the western side of this lough. Several individuals had brood-sacs containing clearly visible eye-staged young.

The Ponto-Caspian fish species, tubenose goby Protherorhinus marmoratus, was recorded for the first time in Poland. Six specimens were captured during April 2008 from rip-rap habitat where the river enters of Włocławski Reservoir, which is situated in the lower section of the Vistula River (Baltic basin). This appears to be the next stage in the species’ westward invasion through the so-called ‘central invasion corridor’ for Ponto-Caspian species. The tubenose goby is, therefore, the fourth alien goby in recent decades to disperse into Polish inland waters, following after the round goby Neogobius melanostomus, the racer goby Neogobius gymnotrachelus and the monkey goby Neogobius fluviatilis.

A new record of the Indo-Pacific red lionfish Pterois volitans (Linnaeus, 1758) (Osteichthyes: Scorpaenidae) is reported for the Dominican Republic, observed in the National Submarine Park of Monte Cristi on May 24, 2008. This is the first official reported record of this species for the Dominican marine area. Preliminary data are provided for the invasion and future work.