Aquatic Invasions is a new on-line journal focusing on biological invasions of the inland and coastal waters of geographic Europe. The journal will form an important tool for the rapid exchange of information pertaining to aquatic invasive species, providing an opportunity for timely publication of first records of biological invaders and hence prompting risk assessment, early warning and eradication programmes. The journal will also provide an opportunity to publish relevant technical reports and other accounts not publishable in regular scientific journals, including large datasets of aquatic invasive species records from monitoring and biological surveys.

The invasive Ponto-Caspian mysid crustacean Hemimysis anomala has been recorded for the first time in the UK in November 2004, and in 2005 at a number of sites in the English Midlands. It occurs in both lentic and lotic environments, including the margins of the relatively fast-flowing River Trent, and large swarms have been observed in one lake. It is not known how the mysid reached the English Midlands, although one site hosts international rowing events.

The Ponto–Caspian predatory cladoceran Evadne anonyx G.O.Sars,1897 (Crustacea: Cladocera: Onychopoda) was first recorded in the eastern Gulf of Finland in the zooplankton samples collected during summer 2000. Most likely, E. anonyx invaded the gulf in the late 1990th from the Caspian Sea via the Volga–Baltic waterway with the ballast waters of ships. Between 2000 and 2004, the population densities of E. anonyx increased in the eastern Gulf of Finland more than 10-fold, indicating successful establishment of new Ponto-Caspian invader in the Baltic Sea.

The Indo-Pacific portunid crab Charybdis feriata (Linnaeus, 1758) was recorded for the first time from the Mediterranean Sea, based on a single adult female caught in a gillnet off Barcelona at a depth of 60-70 m on the 13th December 2004. Its most probable introduction vector was a merchant ship.

The authority of Eriocheir sinensis is often cited as H. Milne Edwards, 1854. However this is not appropriate as Henri Milne Edwards first published a short but valid description of the species in volume twenty of the Annales des Sciences Naturelles, 1853. Consequently this species should be cited as Eriocheir sinensis H. Milne Edwards, 1853. In addition, a recent molecular study of Grapsoidea systematics assigned Eriocheir de Haan, 1835 to the Varunidae Milne Edwards, 1853.

A special survey has been conducted to record the distribution of Chinese mitten crab, Eriocheir sinensis in the eastern Gulf of Finland basin (Baltic Sea). An illustrated questionnaire/registration form was distributed among the commercial fishermen. The survey indicated a significant increase in the abundance of adult crabs in 2003 migrating downstream in the Neva River, the connecting channel between the Gulf of Finland and Lake Ladoga. On October 25, 2005, the Chinese mitten crab was reported from Taypolovsky Bay, Lake Ladoga and this is the first confirmed record from Europe’s largest lake.

Eriocheir sinensis H. Milne Edwards, 1853 has been introduced and established mainly in North East Europe and San Francisco Bay, United States from native China. This note records the first specimen of the Chinese mitten crab from the River Tazeh Bekandeh, Caspian Sea collected on 26 October 2002.

An invasive gastropod, the veined whelk Rapana venosa, was first recorded in July 2005 in the Dutch part of the North Sea, and in September 2005 in the central southern North Sea (the wider Thames estuary). Both shipping activities and natural dispersion from the nearest population in France (Quiberon, Brittany) are possible modes of introduction of R. venosa to these sites. The possible effects of R. venosa in the North Sea remain uncertain, but if established, this invasive species could become a severe competitor for the native whelk Buccinum undatum. As R. venosa is known as predator on bivalves, an impact on local aquaculture activities (on e.g. blue mussels and oysters) is also possible.

Conrad’s false mussel, Mytilopsis leucophaeata has been found in the central Gulf of Finland, which is the first record of this brackish water dreissenid in the northern Baltic Sea. In 2003 a strong recruitment of young dreissenid bivalves was observed and in 2004 dense assemblages consisting of adult M. leucophaeata were discovered in an area affected by cooling water discharges from a nuclear power plant. The introduction of the species has obviously taken place via ballast water transport, resulting in a successful establishment in a favourable warm water environment. Based on the wide salinity tolerance, M. leucophaeata might also colonize areas inhabited by functionally similar bivalves if able to survive the cold winter conditions.

In December 2004 two specimens of round goby, Neogobius melanostomus were caught in the river Lek near Schoonhoven (The Netherlands), which is a first record of this invasive Ponto-Caspian fish in the North Sea basin. After this first observation many individuals have been caught on different locations in the western part of the country. As in the North American Great Lakes and the Baltic Sea, the native fish species could become locally endangered due to competition with new invader. Therefore, the species should be monitored closely to determine its present distribution area as well as the impact on the ecosystem.

After being first detected in the Baltic Sea in early 1990s, the round goby Neogobius melanostomus has expanded its distribution area afterwards and first found in Estonian waters in 2002. There are evidences to suggest that the species is relatively common in leisure fishermen catches at the southern coast of the Gulf of Finland. Thus, this demersal fish is slowly, but continuously colonizing northern parts of the Baltic Sea.

Many ballast water sampling programmes were undertaken in the past to document the number of individuals and variety of species arriving with ships. As no standard ballast water sampling tool exists various sampling devices were used during these studies. When sampling ballast water for compliance control with the Ballast Water Management Convention prepared by the International Maritime Organization a sampling device is needed which documents the number of organisms per water volume discharged. For organisms above 50 microns (in minimum dimension) less than 10 organisms per cubic meter of water are acceptable in the ballast water discharged. Further, ballast water samples need to be taken to assess the efficacy of ballast water treatment systems. As a result more than 1,000 liters of water need to be sampled – and this needs to be carried out multiple times as more than one sampling point, several replicates and various sampling occasions are required. This contribution describes a new sampling device for this ballast water sampling purpose.