Introductions of alien freshwater fish species into the Mediterranean-climatic South-west Coast Drainage Division of Australia have impacted a highly endemic (≈82%) yet depauperate (11 species) native freshwater fish fauna. This study updates the current known introduced freshwater fishes in Western Australia, assesses the historic rate of introductions and how habitat, water quality and climatic changes have facilitated those introductions. South-western Australia has undergone a ≈63% increase in alien freshwater fish introductions since 1970 (44% increase over the past decade) to 13 species; overtaking the number of native fishes. Aquarium species represent 80% of the latest introductions (46% of total number) and the majority (54%) of introduced fishes in the region are of sub-tropical or tropical origin. As found elsewhere, species with broad environmental tolerances and generalist diets are likely to continue to be the main colonizers in this region. We propose that past and future climatic and habitat changes in the Mediterranean-climatic south-west region will facilitate continued invasion of tropical and sub-tropical aquarium fishes and that strategic monitoring, control and public education programs are required to halt future introductions.

The Futaleufú River, Argentina, was monitored monthly from June 2010 to August 2011, in order to detect the invasive diatom Didymosphenia geminata, which was previously observed in Chile. Plankton and periphyton samples were taken from 10 sites. Didymosphenia geminata was not found until late winter. In August 2010, the species was first detected at isolated points of the river but in spring and summer the algal coverage extended along several kilometers. The coverage of blooms, spread to deeper areas (pools) with varying depths, reached more than 2 m, invading epiphytic and epilithic substrates. In autumn the bloom diminished its coverage area and there were only small isolated patches. During the next winter, blooms were not observed until late August, when it was recorded again. The observations showed that D. geminata appeared, colonized and invaded the bed of the river at low flow situations in spring and summer and its blooms declined in autumn - when the flows increase - after having been dried in summer when flows were the lowest.

In 2009 to 2010, 169 American eels, Anguilla rostrata, from the Bras d’Or Lakes, Nova Scotia, were examined for presence of the invasive nematode Anguillicoloides crassus. Prevalence and intensity in eels were determined to be higher than previously reported for the Bras d’Or Lakes. Overall prevalence was determined to be 46% with mean intensity at 9 parasites/eel (±11). Higher prevalence of A. crassus (60 to 67%), higher mean intensities (6.8–12.6 parasites/eel), and greater number of eels with more than 20 parasites per eel were found in semi-enclosed basins with higher freshwater input and close proximity (13 to 20 km) to probable source(s). No significant differences were found between mean intensity between riverine, estuarine or coastal lagoon habitats, however, prevalence was found to be higher in riverine habitats. No significant differences were found between infected and non-infected eels for total length, total body weight, gonad weight, GSI or condition factor. The Bras d’Or Lakes form a semi-enclosed estuarine body with low flushing times, high summer water temperatures (>20°C) and an international shipping destination, that makes it an ideal environment for the establishment and spread of A. crassus. The need to preserve aquatic habitats and reduce environmental stressors is imperative in an A. crassus infected environment. Greater controls and innovative solutions are needed to prevent further introduction of aquatic invasive species.

Four specimens of the invasive red alga Heterosiphonia japonica were collected from Mahone Bay, Nova Scotia, Canada, in August 2012. The identity of these specimens was confirmed using molecular and anatomical evidence. To the best of our knowledge, this is the first report of H. japonica in Canada – an invasive red alga that has been advancing along the northeastern coast of North America since its recent introduction to Rhode Island circa 2007.

The leptothecate hydroid Sertularella mutsuensis Stechow, 1931 is reported on debris from the 2011 Japanese tsunami that came ashore on 5 June 2012 at Agate Beach north of Newport, Oregon. Its discovery on a barnacle (Semibalanus cariosus) from a derelict floating dock originating at Misawa, Honshu, confirms the capability of successful transoceanic dispersal for this species. We compare our specimens to Stechow’s syntype material of S. mutsuensis in collections at the Zoologische Staatssammlung München, and designate a lectotype and paralectotype of the species.

The hydromedusa, Maeotias marginata (Cnidaria, Hydrozoa), was observed in the low salinity (ca 4) archipelago of Southwest Finland in the northern Baltic Sea in August 2012. The species is considered to be native to the Sea of Azov. The only previous records of M. marginata in the Baltic are from 200 km south in western Estonia, in 1999–2003.

The alien Erythraean gastropod Finella pupoides has been recorded at low abundance in the Eastern Mediterranean for over half a century. Recently, its populations along the southeastern Levantine coastline have grown extremely abundant. Samples collected by Israel Oceanographic and Limnological Research surveys during 2010–2011 off the coast of Israel contained up to 3300 ind/m².

In sediment samples collected in the Oosterschelde, a marine embayment in the southwest of The Netherlands (southern North Sea), nine specimens of a non-native myodocopid ostracod were found. The ostracods were identifed as the North American species Eusarsiella zostericola (Cushman, 1906), previously introduced to southeastern England, probably with imported American oysters.

The non-native amphipod Grandidierella japonica Stephensen, 1938 is reported for the first time on the Atlantic coast of mainland Europe, specifically from Marennes-Oléron Bay, France. Likely vectors for this introduction include commercial shellfish transplants and ballast waters. A native of Japan, this species had previously only been reported twice outside the Pacific region; in both cases from coastal waters of England. Adults of both sexes, females carrying eggs, and juveniles were collected in Marennes-Oléron Bay, which suggests the species has become established.

The most northern occurrence in European waters of the Japanese or kuruma prawn Marsupenaeus (Penaeus) japonicus Bate, 1888 is reported from the Celtic Sea. Two specimens were captured during the winter and spring of 2007 from depths ~40 to 60m over mobile sediments by trawling. Other northern European records are reviewed.

The paper presents recent records of the North-American amphipod Gammarus tigrinus and the Ponto-Caspian amphipod Pontogammarus robustoides in Latvian territorial waters of the Baltic Sea. P. robustoides was found for the first time in shallow waters of the Gulf of Riga near Jurmala City in June 2009. During field surveys of 2011–2012, P. robustoides and another invader, the North-American amphipod G. tigrinus (detected earlier in Estonian part of the Gulf), were recorded in different sites of the Latvian waters of the Gulf of Riga and in the coastal Lake Liepaja. Abundance ranged between 1–70 ind./m2 for P. robustoides and 5–100 ind./m2 for G. tigrinus, suggesting they potential role in the functioning of the benthic community in near future.

Two adult specimens of Matuta victor was recently collected in Haifa Bay, Israel. A single specimen of Ashtoret lunaris, collected in 1987 from Haifa Bay, was hitherto the only record of the Matutidae in the Mediterranean Sea.

The introduced Chinese mitten crab, Eriocheir sinensis H. Milne Edwards, 1853, considered amongst ‘100 of the world’s most invasive alien species’, has been well-documented in Europe and North America. Most recently, it was recorded in subtropical western Asia (northern Iran). Here, we report E. sinensis from Singapore; the first record of this species in the wild from the tropics. While the likelihood of establishment of this temperate species in the tropics is low, potentially high and sustained propagule pressure could still allow it to pose a potential threat to native ecosystems and biota, a scenario with precedence in Singapore. Efforts by regulatory agencies are urgently needed to monitor and prevent the introduction of this potential invasive alien species.

A number of Ponto-Caspian gobiid species are currently invading European coasts and freshwaters. They do not only present a nuisance to fishermen, but evidence suggests that they compete with native benthic fishes and may contribute to changes in ecosystem function. This paper reports the presence of round goby Neogobius melanostomus individuals and an established population of bighead goby Ponticola kessleri in the High Rhine.

New records of the rapid spread and establishment of the Erythraean alien apogonid Cheilodipterus novemstriatus along the Israeli coast are presented. In October 2012, a school numbering hundreds of adult specimens was photographed off Rosh HaNikra – a finding that confirms the presence of an established population of the species along the Levantine coast of the Mediterranean Sea.