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European Sea Squirt

Ascidiella aspersa

Report it

If you think you have found an aquatic invasive species:

  1. do not return the species to the water
  2. take photos
  3. note:
    • the exact location (GPS coordinates)
    • the observation date
    • identifying features
  4. contact us to report it
European sea squirt is a solitary tunicate that is often found in dense unfused aggregations.

European sea squirt is a solitary tunicate that is often found in dense unfused aggregations.

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Origin and distribution

Map showing the Canadian Maritime Provinces: Nova Scotia (N.S.), New Brunswick (N.B.), Prince Edward Island (P.E.I.). Their surrounding coastal waters are divided into subregions, which are outlined in black. Areas that have green shading indicate that European Sea Squirt has been observed in subregions: 1: Bay of Fundy (N.S.), 2: Southwest (N.S.), 4: Cape Breton (N.S.), 6. Bay of Fundy (N.B.).

Observed distribution of European Sea Squirt in subregions of Canada's Maritime provinces.

Note: Observation within a subregion does not mean the species is found throughout it. Lack of observation within a subregion does not mean the species is absent from that subregion. It means that it has not been observed there.

The European Sea Squirt is native to Europe. The species was first introduced in the United States in New England in the 1980's and can now be found in most of the Gulf of Maine. It was first detected in Canada on the south shore of Nova Scotia in 2012. To date, it has spread within Nova Scotia and to the Bay of Fundy coast of New Brunswick, but has not been observed in other Canadian provinces.

Identifying features

Similar species

Sea grapes, sea potatoes and sea peaches are native solitary tunicates, but they are shaped differently and may be found individually or in small clumps. For example, sea grapes are spherical with 2 siphons close together at the top.

Among invasive species, European Sea Squirts may be mistaken for Vase or Clubbed tunicates but their shape, tunic surface and color are different. In addition, the European Sea Squirt has 1 siphon on top and 1 on the side (at approximately one third of its body length).

Ecological and economic impacts

European Sea Squirt

European Sea Squirt

Potential impacts of a European Sea Squirt invasion are widespread. The species grows rapidly and can tolerate a wide variety of conditions, making it a major biofouling pest. This species may outcompete other organisms for food and space, thereby altering the natural community dynamics. Moreover, it threatens aquaculture, fishing and other coastal and offshore activities. The European Sea Squirt leads to an increase in the weight of the aquaculture cultivation gear, causing work to be more demanding. Which results in an increase of the operating costs for shellfish producers and processors.

Mode of arrival

European Sea Squirt was most likely introduced to North America through hull fouling and/or ballast water.

European Sea Squirt. Credit: B. Vercaemer.

European Sea Squirt. Credit: B. Vercaemer.

Government action

Scientific research

Fisheries and Oceans Canada is monitoring the distribution of invasive biofouling species (that is, aquatic species that live attached to hard surfaces) on the Atlantic and Pacific Coasts to detect new invasions and track the spread of European Sea Squirt.

For further information

References

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