A non-native population of plains minnow Hybognathus placitus in the Pecos River, New Mexico, USA, replaced the endemic, ecologically similar Rio Grande silvery minnow Hybognathus amarus in less than 10 years. Competitive exclusion is hypothesized as a mechanism of replacement. The following evidence was examined for potential support: (1) the historical population trend of H. amarus versus H. placitus; (2) relative suitability of the modified flow regime for H. amarus versus H. placitus; (3) potential for habitat overlap; and (4) spawning periodicity and body length in the non-native population of H. placitus. Historical data indicate H. amarus did not decline until H. placitus was present, after which it disappeared rapidly and H. placitus proliferated. The natural flow regime of the Pecos River was changed via base-flow reductions and capture of spring-snowmelt runoff, making it similar to flow regimes associated with likely source populations of non-native H. placitus. Spring runoff is an important spawning cue for H. amarus, but not H. placitus and H. placitus appears to be naturally more tolerant of diminished streamflow. Extant H. placitus were associated with a relatively pristine river reach that was most likely the stronghold for the replaced H. amarus population. Given high ecological similarity, habitat overlap was likely high during the period of replacement. Hybognathus placitus in the Pecos River had a protracted spawning season (April through September), whereas extant H. amarus in the Rio Grande had a short spawning season (a few days in May or June during snowmelt runoff). Most H. amarus die after their first spawning season and few exceed 60 mm standard length (SL), whereas quite a few H. placitus survive at least until their second spawning season and exceed 60 mm SL. Co-occurrence of multiple spawning cohorts may stabilize annual reproductive output of H. placitus and larger individuals may be more fecund and produce larger eggs that survive better. Spawning flexibility, greater size, and higher environmental tolerance likely gave H. placitus a reproductive and survival advantage over H. amarus, consistent with a deterministic pattern of rapid species replacements in the plains, in which tolerant, competitive species from the Red River drainage or Gulf of Mexico coast rapidly replace more sensitive, endemic congeners in disturbed, remnant habitats.

The introduced range of the European cyprinid, sunbleak Leucaspius delineatus, in England was previously limited to parts of southwest England but has now expanded across Southern England. Natural dispersal mechanisms cannot explain their increased distribution and fish stocking was not a factor. Thus, the accidental movement of either their eggs or larvae via anglers’ nets was believed to be the mechanism by which these fish were accidentally moved between waters over 100 km apart. This dispersal pathway is difficult to regulate, as is the release of unwanted non-native aquarium and pond fish into open waters by the public. This latter pathway has resulted in the recent releases of species including walking catfish Clarias batrachus, Asian weatherfish Misgurnus mizolepis and white catfish Ameiurus catus.

The Southern Hemisphere unitary ascidian Corella eumyota was discovered in 2002 in France and is now widespread on the southern coast of England and in Ireland. It has also been reported from seabed surveys in Ría de Vigo, north-west Spain. Surveys of marinas in February 2008 and June-July 2009 identified additional localities in Ría de Vigo and revealed widespread occurrence of C. eumyota on the Atlantic coast of the Iberian Peninsula. The species was very abundant on some structures built less than two years before the surveys, indicating a capacity for very rapid colonization and population increase. This suggests that the species is a potential threat to biodiversity and aquaculture interests. Records of the non-native ascidians Styela clava, S. plicata, Perophora japonica, Botrylloides violaceus, and Didemnum vexillum are also reported.

The ascidian Corella eumyota, originally from the Southern Hemisphere, was first reported in the Northern Hemisphere in Brittany, France, in 2002. Since then, it has been recorded in Spain, Ireland, the south coast of England and South Wales. Most European records to date have been from artificial habitats such as marinas. In Plymouth, England, C. eumyota was first found in two marinas in 2005 but individuals were soon also detected in small numbers on nearby shores. Shore surveys in March and August of 2008 indicated that C. eumyota has established reproductive populations on natural and semi-natural shores of Plymouth Sound and the adjacent coastline, largely restricted to relatively sheltered sites in the lower reaches of estuaries. At these sites it is generally the most abundant non-colonial ascidian. The species clearly has the capacity to become a significant component of the biota of sheltered shores in the Northern Hemisphere.

This paper presents new records of Asian clam Corbicula fluminea in the rivers Mero, Sil and Deva. Records from the Rivers Sil and Deva showed the increase of its spread in the Miño river basin. Findings in the Mero basin represented the first Iberian record of this species outside the Miño basin. Furthermore, it was the most north-western record in the Iberian Peninsula.

The paper presents the first record of the Ponto-Caspian amphipod crustacean Pontogammarus robustoides G.O. Sars, 1894, in the Gulf of Riga, Baltic Sea. Eight individuals of this invasive amphipod were found in June 2009, in shallow waters of the gulf near Yurmala city. Most likely this species entered the Gulf of Riga from Latvian rivers emptying into the Baltic Sea, where it was previously found. However, introduction via ships coming from either southern or north-eastern parts of the Baltic Sea is also a possibility.

In 2008, the killer shrimp, Dikerogammarus villosus, native to the Ponto-Caspian region, was found for the first time in Central Italy, in Bilancino, an artificial lake situated in the watershed of the River Arno (Tuscany). This new record shows that this species’ range is expanding in Italy. It is thus imperative to identify the pathways and vectors of spread of this species in order to halt this invasion process.

The Japanese shore crab Hemigrapsus sanguineus is recorded for the first time from a Black Sea locality: Tomis Marina in Constanţa, Romania. The suggested vector of introduction is as adults in the hull fouling of yachts. The species has not established and salinity requirements for larval development make it unlikely that it will ever establish in the Black Sea.

A single female specimen of the blue crab Callinectes sapidus Rathbun, 1896 was captured by a fisherman on 26 May 2008 in the East Frisian Wadden Sea, National Park of Lower Saxony, Germany. The specimen was transferred to a public marine aquarium in Dorumersiel. On 9 June 2008 the female extruded masses of fertilized eggs. Due to nature conservation efforts in this national park, management instructions are implemented by the appropriate authority for further dealing with the captured specimen and its potential offspring. This is the second record of a mature female and the first record of a fertilized female blue crab from German coastal waters of the North Sea.

The presence of the blue crab Callinectes sapidus has been recently recorded in the Lagoon of Patok. Twelve individuals from this lagoon have been observed and measured during October 2009. Based on carapace measurements most of these crabs can be considered as mature. The population of the blue crab seems to be increasing and can be considered as established in Patok area.

We register here the first occurrence of the “dourado” Salminus brasiliensis (family: Characidae) in Salto Santiago Reservoir in the Iguaçu River basin, Paraná State, Brazil, a global biodiversity ecoregion with an extremely rich endemic ichthyofauna. The single specimen captured, an adult female measuring 480-mm total length, was taken with gillnet in January 2008. No additional S. brasiliensis were captured during general fish surveys conducted at four sites in the reservoir even though multiple types of gear were used (gill and trammel nets and long-line fishing) over a period of nearly two years (bimonthly from July 2006 to September 2008). The presence of S. brasiliensis, a large, predacious freshwater species native to other parts of Brazil, may be related to its use as a sport fish, and the single specimen taken from the reservoir may have escaped from ponds built by aquaculturists for recreational angling. Before appropriate management measures are taken, additional field work is needed to determine the status and distribution of S. brasiliensis in the Iguaçu basin and to assess possible negative effects of the introduction on native fishes.

We recorded the first sighting and collection of the non-native, invasive Red lionfish (Pterois volitans [Linnaeus, 1758]: Scorpaenidae) in the southern Gulf of Mexico, off the northern Yucatan Peninsula. In December 2009, two individuals were sighted (one of them speared) at 38 m depth over a reef formation, about 58 km northwest of the Alacranes Reef National Park, which is located 130 km off the northern coast of the Yucatan Peninsula, Mexico. More than 20 years after the introduction of P. volitans into the western Atlantic, specifically off the Florida and North Carolina coasts, the invasion circuit now appears to be closing in, since this new record was made about 800 km from the Dry Tortugas and Marquesas, Florida. This recording appears to be the first introgression of the P. volitans population into the Gulf of Mexico via larval transport.

A single specimen of Priacanthus sagittarius was captured by a commercial trawler off the Mediterranean coast of Israel on 28th November 2009. This is the first record of the species, and possibly the first alien member of the Priacanthidae from the Mediterranean Sea.

The Emperor angelfish Pomacanthus imperator (Bloch, 1787) was recorded for the first time from the Mediterranean. Its occurrence there is due to either migration from the Red Sea (Lessepsian migration) or escapee from aquarium trade. The Spotbase burrfish Cyclichthys spilostylus (Leis and Randall, 1982) was recorded for the second time in the Mediterranean, close to two decades after the first record.