In 2007, the invasive ctenophore Mnemiopsis leidyi was observed for the first time in Limfjorden (Denmark) where it exhibited mass occurrence in late summer while the indigenous and usually dominating common jellyfish, Aurelia aurita, was nearly absent. Both species were further studied in 2008 and 2009 and it was found that the additional predation pressure by M. leidyi caused the zooplankton stocks to be severely depressed. Here, we report on the population dynamics and predation impact of M. leidyi and A. aurita in Limfjorden in 2010 and 2011. In 2010, M. leidyi was observed in Limfjorden for the first time in August with the highest density and largest size in the central parts (Skive Fjord). The estimated half-life of zooplankton (copepods) was only important in Skive Fjord in mid August 2010 when the joint-predation impact of A. aurita and M. leidyi was 2.3 d. In 2011, no M. leidyi were observed on the first cruise (3 August), while during the second cruise (17 November) it was observed in large numbers. The western most location (Venø Bugt) was dominated by large sized (≤ 60 mm) M. leidyi, while the average size decreased towards the central parts of the fjord-system. The proportion of cydippid larvae increased from west to the central parts thus suggesting rapid reproduction and population-size expansion. The bio-volumes of ctenophores were highest in the central part with 85 ml m^-3 in Løgstør Bredning, which may be compared to the greatest mean bio-volume of about 184 ml m^-3 observed in the Black Sea in 1989 when the zooplankton and fish stocks collapsed. Analysis of available hydrographic data and model calculations indicates that re-invasion of M. leidyi from the North Sea seeded the autumn population in Limfjorden in mid-September.

The freshwater invasive mollusc Dreissena polymorpha and its host-specific commensal ciliate Conchophthirus acuminatus represent a convenient model to study various aspects of symbiotic relationships. This study was conducted to test whether the nutrient enrichment of waterbodies inhabited by D. polymorpha is associated with C. acuminatus infection. Three lakes differing in their trophic conditions were simultaneously sampled to estimate the levels of C. acuminatus infection in D. polymorpha (eutrophic Lake Batorino, moderately eutrophic Lake Myastro, and mesotrophic Lake Naroch, Republic of Belarus). Although the percentage of infected molluscs did not differ among these waterbodies, the average number of ciliates per host showed a significant increase with respect to the lake trophic status. This pattern could be explained by favorable feeding conditions experienced by D. polymorpha and its commensal C. acuminatus in waters of higher trophy. In particular, the average size of D. polymorpha (i.e., carrying capacity for the infection) significantly positively correlated with the lake trophic status. Higher trophy could also directly affect reproduction potential of the ciliate C. acuminatus, which supposedly feeds on bacteria, algae, and other organic particles filtered out from the water by its host. The results of this study may apply to a wider spectrum of similar commensal associations in fresh waters.

The control strategies for any marine invasive species that is edible may include their use as food for human consumption. The potential and realized use of the invasive Indo-Pacific green mussel, Perna viridis (Linnaeus, 1758) for food in Jamaica, from wild populations in Kingston Harbour, underscored the importance of investigating the potential public health risks to consumers from mussels fished from different areas of Kingston Harbour. Levels of bacterial coliforms and heavy metals were examined during this investigation due to the nature of pollutants already documented in Kingston Harbour. Bacterial coliforms showed high levels (15 – >16,000 MPN/100mL) at five stations during the investigation, with the highest values at the station located adjacent to the Hunts Bay Power station (HBPS). Heavy metals, especially chromium and cadmium were also high (43.3–70.3 mg/kg (chromium) and 17–60 mg/kg (cadmium)), with highest value at the station GC (Goodbody’s Channel) for chromium and Station DT (Kingston Waterfront) for cadmium. The risks to public health through consumption of these green mussels, Perna viridis from Kingston Harbour are significant. If consumption of wild populations from Kingston Harbour is to be promoted to reduce the population number of this invasive species, then depuration of the mussels prior to consumption should be carried out.

We report on the occurrence of South American suckermouth armored catfishes (Loricariidae) in the Suwannee River basin, southeastern USA. Over the past few years (2009-2012), loricariid catfishes have been observed at various sites in the Santa Fe River drainage, a major tributary of the Suwannee in the state of Florida. Similar to other introduced populations of Pterygoplichthys, there is high likelihood of hybridization. To date, we have captured nine specimens (270-585 mm, standard length) in the Santa Fe River drainage. One specimen taken from Poe Spring best agrees with Pterygoplichthys gibbiceps (Kner, 1854) or may be a hybrid with either P. pardalis or P. disjunctivus. The other specimens were taken from several sites in the drainage and include seven that best agree with Pterygoplichthys disjunctivus (Weber, 1991); and one a possible P. disjunctivus × P. pardalis hybrid. We observed additional individuals, either these or similar appearing loricariids, in Hornsby and Poe springs and at various sites upstream and downstream of the long (> 4 km) subterranean portion of the Santa Fe River. These specimens represent the first confirmed records of Pterygoplichthys in the Suwannee River basin. The P. gibbiceps specimen represents the first documented record of an adult or near adult of this species in open waters of North America. Pterygoplichthys disjunctivus or its hybrids (perhaps hybrid swarms) are already abundant and widespread in other parts of peninsular Florida, but the Santa Fe River represents a northern extension of the catfish in the state. Pterygoplichthys are still relatively uncommon in the Santa Fe drainage and successful reproduction not yet documented. However, in May 2012 we captured five adult catfish (two mature or maturing males and three gravid females) from a single riverine swallet pool. One male was stationed at a nest burrow (no eggs present). To survive the occasional harsh Florida winters, these South American catfish apparently use artesian springs as thermal refugia. In the Santa Fe River, eradication might be possible during cold periods when catfish congregate in spring habitats. However, should Pterygoplichthys increase in number and disperse more widely, the opportunity to eliminate them from the drainage will pass.

The predation of invasive signal crayfish, Pacifastacus leniusculus (Dana, 1852) by several nesting pairs of lesser black-backed gull, Larus fuscus Linnaeus, 1758 is reported from Steep Holm (51°20.39' N, 3°6.53' W), one of two small islands located in the inner Bristol Channel, United Kingdom. This feeding activity was subsequently observed at a pond in South Wales.

Two invasive bryozoan species were discovered at Dun Laoghaire Harbour, Dublin during a bryozoan survey. Watersipora subtorquata (d’Orbigny, 1852) and Tricellaria inopinata d’Hondt and Occhipinti Ambrogi, 1985 were discovered in Dun Laoghaire marina. Research shows that this is a first record for W. subtorquata in Ireland and a range extension for T. inopinata. In recent years the numbers of invasive marine species in Ireland has increased. The presence of these species within the marina and not in areas surrounding the marina suggests that they have been spread via shipping activities.

The invasive New Zealand mudsnail, Potamopyrgus antipodarum, is a small freshwater hydrobiid snail with populations in western US rivers and streams and in the Laurentian Great Lakes. The snail has had established populations in the Great Lakes since at least 1991 and in one stream emptying into Lake Ontario since at least 2007. This study’s purpose was to broadly survey streams and rivers emptying into Lakes Ontario and Erie to determine the extent of the species’ lotic invasion in the Eastern US. In the summer of 2011, over 100 sites were sampled from the Niagara River, NY to Oswego, NY along Lake Ontario and over 80 sites from Buffalo, NY to the Pennsylvania-Ohio State line along Lake Erie. At each site, general observations of the stream were made and the organisms living in the stream were surveyed for the presence of New Zealand mud snails. Potamopyrgus was found at the site of original discovery and at one additional location along Lake Ontario. In addition an unusual snail was discovered that was a hybrid between a native species (Pleurocera livescens) and an invasive (Pleurocera virginica). This hybrid was extremely abundant in several locations and may be invasive.

The alien sacoglossan opisthobranch Elysia grandifolia, first recorded in the Levantine basin, eastern Mediterranean Sea, in 2001, has established a flourishing population along the Mediterranean coast of Israel. In August 2012 large numbers were observed on bryopsidacean-covered rocky outcrops off the central Mediterranean coast of Israel. Pairs of specimens and clusters of several individuals with extended penes may be copulatory aggregations.

On December 1st 2011, five specimens of the broadbanded cardinalfish Apogon fasciatus (White, 1790) were captured from the Gulf of Antalya. This observation documents the westward expansion of this alien species along the Turkish coasts.

On 12 May 2012, two individuals of Champsodon nudivittis were captured off the coasts of Rhodes Island, southeastern Aegean Sea, at 150 m depth. This finding suggests a rapid geographical extension of this Indo-Pacific species along the northeastern Levantine coast of the Mediterranean. With C. nudivittis, the number of Lessepsian fishes recorded in the Aegean Sea is raised to 31.