The examination of native habitats of newly introduced species is one of the factors that can provide information for predicting and preventing invasion success. In this study, we investigated the distribution patterns of a green macroalga, Codium fragile, in its native range in Korea. There were two distinct patterns for Codium spp. within their native habitat. In undisturbed communities, Codium species were members of the understory assemblage below the dominant canopy species. In disturbed habitats where native algae have been harvested for food, the activity created major gaps in the community structure where opportunistic algae expanded their abundance within the community. Codium fragile not only becomes a dominant canopy species in disturbed habitats, but it also colonizes new habitats such as fouling communities. Thus, the distribution patterns of Codium fragile in its native range suggests that it has the capability of taking advantage of disturbed habitats, which may help to explain why it has been such a successful invader in other regions of the world. One interesting finding was the lack of specialized sacoglossan herbivores associated with the Korean populations studied while such herbivores do feed on introduced populations in other regions, and may limit their distribution at some locations.

Forty-two specimens of Macrobrachium nipponense (de Haan, 1849) were collected from Abu-Zirig Marsh in the south of Iraq, in July 2005. DNA sequences confirmed the morphological identification by 99 % similarity to published 16S sequences. The introduction vector for this non-native species into the wild is considered to be unintentional escapes from Iranian aquaculture.

The Baltic palaemonid fauna comprises four species: Palaemonetes varians, Palaemon adspersus and two newcomers, P. elegans and P. longirostris. The first three species have been reported from Polish waters. This paper presents the history of faunal change associated with P. elegans recent colonization along the Polish Baltic coast, its estuaries, coastal lakes and lagoons. The oldest record of P. elegans comes from the Vistula deltaic system collected in 2000. Presumably moving eastwards from the Atlantic, the species colonized and formed a vivid, reproducing population all along the studied part of the Baltic shores. In many places it has replaced the native P. adspersus and it has became an abundant element of the palaemonid community in the Gulf of Gdańsk and in the Vistula delta, still accompanied by the two other species.

The present study reports the occurrence of three Indo-Pacific gastropod species at new localities in the Mediterranean Sea. Chromodoris quadricolor was recorded on the 29 May 2004 in the eastern Mediterranean, which is the third report of the species from the Mediterranean Sea. Finella pupoides and Syrnola fasciata are collected from the several sites in the Aegean Sea between 1997 and 2002. The morphological, ecological and distributional characteristics of these species are described.

Percnon gibbesi (H. Milne Edwards, 1853) is reported for the first time from the southern coast of Turkey in 2005-2006. This grapsid crab is the most invasive decapod species to enter the Mediterranean, it was first recorded in 1999 in the Balearic Islands, Sicily and adjacent islands. Possible vectors for its rapid spread across the Mediterranean include larval transport by surface currents and shipping.

The tropical Atlantic grapsid crab Percnon gibbesi (H. Milne Edwards, 1853) may be regarded as the most invasive decapod currently expanding its distribution in the Mediterranean Sea. The present paper records its presence in Greek waters since 2004. The species seems well established along the coasts of Messiniakos Gulf, Crete and Rhodes Islands as several individuals of various sizes were observed on shallow, rocky bottoms. The proximity of these localities to ports may hint at shipping as potential vector, but larval transport from already established populations across the Ionian Sea cannot be excluded. The wide adaptability, the potential for colonising new habitats and the population dynamics of P. gibbesi merit further investigation.

We report here the first Chinese mitten crabs, Eriocheir sinensis H. Milne Edwards, 1853, found in the Chesapeake Bay, USA. Two male specimens were caught, retained, and identified from the mouth of the Patapsco River, near Baltimore, Maryland. The first crab to be reported was captured on 9 June 2006. Surprisingly, the second reported crab was captured at least one year earlier, probably in May 2005. Another two specimens of E. sinensis were reported up to 90km south of this location in April-June 2006, but the identity of these latter crabs could not be confirmed, because the specimens were not kept. Environmental conditions in Chesapeake Bay appear suitable for colonization by E. sinensis, and it is presently not known whether mitten crabs are reproducing or established in the region.

A colonial Didemnum sp. was found extensively overgrowing fouling organisms on the immersed surfaces of pontoons, ropes and chains and on the hulls of fouled pleasure craft in the Malahide Estuary to the north of Dublin in October 2005. The tunicate colonies formed pendulous growths extending ~1m on a yacht removed from the water in June 2005, but its significance at that time was not realised. A similar but less extensive cover by a Didemnum sp. was noted at a marina in Carlingford Lough, ~70km to the north of Malahide, in June 2006. Both sites are exposed to marine conditions on the east coast of Ireland in the Irish Sea. These forms have not been noted in Ireland before and may have recently arrived.

The Ponto-Caspian amphipod Obesogammarus obesus (Sars, 1894) was first recorded in the Rhine River near Koblenz, Germany in October 2004. Additional records of small numbers of O. obesus from the same location in 2005 and 2006 indicate that this alien species may have become established in the central section of the Rhine River. Ship transport via the Main-Danube Canal, connecting the Danube basin (Black Sea catchment area) and the Rhine basin (North Sea catchment area), is the plausible mode of introduction of O. obesus to the site at Koblenz. The possible ecological effects of O. obesus in the Rhine River remain uncertain and require further study. Based on the invasion history of other Ponto-Caspian amphipods, it can be speculated that O. obesus will extend its distribution within the German and European river and canal systems in the near future.

Aquatic biotopes are, due to their unique features, among the most disposed ecosystems to bioinvasions. Serbian waters are not an exception, with a increasing colonization by allochthonous organisms observed there during the last few decades. Non-indigenous aquatic species were found among plants, vertebrates and invertebrates. One of the most invasive aquatic macroinvertebrate species found in the region is the Chinese pond mussel Anodonta (Sinanodonta) woodiana (Rea, 1834). The species is dispersed along lowland rivers, associated wetlands and manmade canals. Heavily modified and artificial aquatic habitats, with high silting rates, were found to be especially suitable for population by A. woodiana. A mass occurrence of Chinese mussel was observed among these habitats, particularly where bottom substrata were characterised by the domination of silt-clay.

On 23 July 2003, a new, previously unreported, molluscan species Lithoglyphus naticoides (gravel snail) was found in the benthos of Lake Lukomskoe, Belarus. As Dreissena polymorpha (zebra mussel) is also present, Lithoglyphus naticoides is the second Ponto-Caspian species recorded in this waterbody. Previous long-term observations on benthos and L. naticoides abundance data obtained in 2003-2005 imply that this species appeared in the lake in approximately 2000 and that currently its population is growing. We review available information on distribution of the snail in both Belarus and in adjacent countries and also discuss possible invasion pathway into Lake Lukomskoe.

The early life stages of Dreissena polymorpha were studied in Lough Key, Co. Roscommon, Ireland during the reproductive season, 1998-2003. This involved weekly sampling of larval/veliger density, size distributions and settlement density. Low larval and adult densities of Dreissena in 1998 indicated that this was the first year of significant reproduction in Lough Key. Variation existed in seasonal larval densities, larval size distributions and juvenile settlement patterns among sampling weeks, years and monitoring sites from 1998 to 2003. In the early years of invasion (1998-2000) annual variations were observed in larval density and juvenile settlement. Increasing levels of larval density and settlement from 1998 to 2000 were typical for the early exponential growth phase of Dreissena invasions. The high level of successful recruitment in those years was evident from the exponential increase of the adult zebra mussel population. In subsequent years, these differences were likely related to environmental variations in summer water temperatures and food availability for veligers. In 2001, settlement estimates were extremely low relative to the larval densities present. Prolonged warm water temperatures in summer 2003, resulted in a long reproductive season and also high settlement rates. The variation between annual datasets observed in this study, implies that long term studies of the early life stages of Dreissena polymorpha is required to monitor the dynamics of this species within lake ecosystems.

Paddlefish Polyodon spathula was recently found in the lower River Danube of Serbia. Its introduction in the Danube is most likely to result from fish escaping from Romanian or Bulgarian rearing facilities where it was introduced in the 1990’s. It now occurs as far up as the Iron Gate II (863 – 862 km from the Black Sea) and appears to have acclimatised to the lower River Danube.

A single immature female specimen of the blue crab, Callinectes sapidus Rathbun, 1896 was collected on 22 September 2004 in a refrigeration pipe of the power station at Port of El Musel, Gijón, Northern Spain. This is the first record of this alien species from northern Spain.

The needle-spined urchin, Diadema setosum, reported on 12 August 2006 from the southern coast of Turkey, is the first Erythrean alien echinoid to enter the Mediterranean Sea. Possible vectors include larval transport through the Suez Canal, shipping, and aquarium trade. The urchin’s venomous spines may cause painful injuries to swimmers.

To date, only one species of Erythrean stomatopod, Erugosquilla massavensis (Kossmann), has been reported from the Mediterranean Sea. We report the first appearance of a second Erythrean stomatopod species from the Mediterranean coast of Israel, Clorida albolitura Ahyong & Naiyanetr, on 24 May 2006.

The scyphomedusa Rhopilema nomadica, recorded in July 2006 from Lakonikos Gulf, on the Ionian coast of Greece, is a Lessepsian alien established in the Levantine Sea. The jellyfish’s painful stings may pose a danger to swimmers. Because of its invasiveness and its impact it is considered among the worst invasive marine species in European Seas.

To date, three alien scyphozoan species were reported from the Eastern Mediterranean, but only one, Rhopilema nomadica, was reported from the Turkish coast. Recently, a second alien scyphozoan, Cassiopea andromeda, was collected on 20 July 2005 in Iskenderun Bay, SE Turkey.