NEMESIS Bioregion Distribution:

Native  Introduced  Cryptogenic  Failed

First Non-native North American Marine/Estuarine Record: 1894
First Non-native West Coast Marine/Estuarine Record: 1965
First Non-native East/Gulf Coast Marine/Estuarine Record: 1894

General Invasion History:

Gonionemus vertens is native to the North Pacific, from Vietnam to the southern Sea of Okhotsk in the Western Pacific, and from Puget Sound, Washington to the Aleutian Islands in the Eastern Pacific (Edwards 1976; Naumov, in Golikov et al. 1976; Mills et al. in Carlton 2007). Asian populations are reported to cause more severe stings, both as polyps and medusae, than those on the Pacific coast of North America (Edwards 1976). Edwards noted considerable local variation in morphology of medusae, but considers this to be environmental or genetic differences at the sub-specific level. It is possible that several cryptic species are present over its broad Pacific range. Medusae of G. vertens appeared suddenly in 1894 in Woods Hole, Massachusetts near the Marine Biological Laboratory, and then appeared in a number of lagoons and harbors in Europe, often near marine laboratories. This hydrozoan is prone to sporadic 'blooms' of medusae, followed by disappearances, while its polyp phase is easily overlooked – hence Edwards (1976) title, 'A study in erratic distribution'.

North American Invasion History:

Invasion History on the West Coast:

On the West coast, a population of G. vertens was found in a lagoon on the campus of the University of California at Santa Barbara, far south of its normal range, first appearing in 1965 (Edwards 1976).

Invasion History on the East Coast:

In 1894, G. vertens appeared in the Eel Pond lagoon, adjacent to the Marine Biological Laboratory in Woods Hole, Massachusetts, where it had not been seen previously. It was subsequently found in eelgrass beds (Zostera marina) in surrounding locations, including Hadley Harbor in the Elizabeth Islands, Vineyard Haven, and Muskeget Island (Mayer 1910; Sumner et al. 1913a). The medusa was also collected in Noank, Connecticut in Long Island Sound (Mayer 1910). It became a frequent experimental animal at Woods Hole, but disappeared after a massive, widespread, eelgrass die-off in 1931. Edwards (1976) considered it extinct on the East Coast, but Gosner (1978) noted it as 'erratic' since the 1930s. Recently, this medusa has re-appeared in tidal salt ponds on Cape Cod and Martha’s Vineyard, where it stung researchers. In 2006, G. vertens was discovered in Farm Pond, Martha's Vineyard, and later in Menemsha Pond (Friends of Farm Pond 2012). In 2010, it was found in Sedge Lot Pond, adjacent to Waquoit Bay in Mashpee (Kehrl 2011). Gonionemus vertens appears on a checklist for Cobscook Bay, Maine, but no details are provided (Trott 2004). Edwards (1976) suggests that a possible vector for this hydrozoan was shellfish research by the US Fisheries Commission, which included rearing and stocking of Pacific Clams (Protothaca staminea), or more likely, oysters from Europe, possibly including the 'Portuguese' Oyster (Crassostrea angulata), with which the polyp could have been carried from Asia. Ballast water or hull fouling is less likely, as they could not account for the highly localized distribution on the East Coast. In June, 2016, several specimens of G. vertens were discovered in New Jersey estuaries, in Shrewsbury River, Manasquan Bay, and Barnegat Bay (Goldman 2016; Gaynor et al. 2016). Genetic barcoding indicated that these specimens were a close match with G. vertens from China (Gaynor et al. 2016). Severe stinging, due to this jellyfish, has not been reported in New Jersey, to our knowledge.

The recent occurrence, since the 1990s, of severely stinging G. vertens in Martha's Vineyard and Waquoit Bay waters may represent a cryptic invasion of the more severely stinging Northwest Pacific form of this hydrozoan (Govindarajan and Carman 2015).

Invasion History elsewhere in the World:

In Europe, Gonionemus vertens medusae were first reported in aquaria at Dove Marine Laboratory, in Cullercoats, on the North Sea coast near Scotland (in 1913, Edwards 1976). There have been many subsequent records, many of them from aquaria in marine laboratories or private homes, but these often contained stones gathered from nearby shores. Several of the laboratories had been engaged in oyster research (Edwards 1976). Elsewhere in Europe, G. vertens medusae (and later, polyps) were found in 1929 at Callot, France, near Roscoff in Brittany (Teissier 1965, cited by Edwards 1976), again in an area of heavy oyster cultivation. Other appearances in Europe were at Ostend, Belgium in 1946; the island of Sylt, Germany in 1947; the Rammekenshoek creek, near Middelburg, the Netherlands in 1960; and Lake Grevelingen, the Netherlands (Edwards 1976; Bakker 1980; Wolff 2005). Further north, medusae were found in the Oslofjord, Norway in 1921; the Gullmar Fjord, Sweden in 1930; and the more northern Hardangerfjord, Norway in 1958 and Trondheimsfjord, Norway in 1969 (Tambs-Lyche 1964; Edwards 1976; Hopkins 2002). Gonionemus vertens appeared in the outer Baltic at Frederikshavn, Denmark in 1960, but did not become established (Edwards 1976; Jensen and Knudsen 2005). In the Mediterranean, there are some early records, from 1876 to 1950, from the French coast and Adriatic (Edwards 1976; Bouillon et al. 2004), but we have not found more recent reports and are uncertain of its establishment. Edwards (1976) considered oyster culture, particularly the 'Portuguese' oyster (C. angulata), introduced from Asia in the 16th-17th century, to be the likeliest vector for the introduction of this hydrozoan to Europe.

In September 2008, medusae of G. vertens were found in an aquarium filled with benthic organisms collected near Mar de Plata, Argentina, the first record of this hydrozoan in the Southwest Atlantic. Shipping is the likely vector of this introduction (Rodriguez et al. 2014b).

In June 2016, G. vertens was found in the Berre Lagoon on the Mediterranean coast of France. In July 2017, this jellyfish was associated with severe stinging of swimmers, including several cases of anaphylactic shock. Environmental restoration of the lagoon, including the recovery of Eelgrass (Zostera marina) may have favored the establishment of G. vertens. Past pollution may have also contributed to abnormalities in the medusae (Marchessaux et al. 2017).