Pancake Batter Tunicate
Didemnum vexillum

Also called: Didemnum, colonial tunicate, sea squirt, ascidian, the blob.

Report a discovery in an unlisted area

If you think you’ve seen or caught a Pancake Batter Tunicate:

  • Do not release it into the water.
  • Catch it and keep it frozen. If you can’t do that, destroy it.
  • Note the location (with GPS coordinates if possible) as well as the observation date.
  • Contact Fisheries and Oceans Canada.

Didemnum is an invasive colonial tunicate native to the Pacific. Is has been observed on the west coast, It has not yet been observed in eastern Canada, although it is present nearby on the eastern coast of the United States.

Identifying features

A colonial tunicate; colour ranges from orange to tan; often colonies will produce lobes; dark lines (channels) may run randomly through the tunicate and a ‘spotted’ appearance might be observed due to white, calcareous spicules embedded in the tunic. The colonies are dense and look like pancake batter. Species is most often confused with native sponges (check for a gelatinous texture compared to a soft spongy texture) or native tunicates (check for white spots in Didemnum vexillum).

Similar species (native)

Pancake Batter Tunicate can be mistaken for other invasive tunicates such as the violet tunicate, but it do not come in red or orange It may resemble certain types of sponges, but their texture is gelatinous rather than spongy.

Where it has been found

In British-Columbia this species has been reported in the Strait of Georgia (Thetis Island, Okeover Inlet, Agamemnon Channel) and the west coast of Vancouver Island. (Lemmens Inlet). In 2013, this species was confirmed in the Minas Basin off of Parrsboro, Nova Scotia.


Tunicates are typically found in sheltered areas, attached to rocks, eelgrass, seaweeds, other animals or on man-made structures such as boat hulls, buoys, ropes, anchors, floating docks, aquaculture gear and wharf pilings.

Ecological and economic impact

Due to the aggressive colonizing abilities the Pancake Batter Tunicate may outcompete other organisms for food and space, thereby altering the natural community dynamics. It may also threaten aquaculture, fishing and other coastal and offshore activities, increase the weight of the aquaculture cultivation gear, causing work to be more demanding. This leads to an increase of the operating costs for shellfish producers and processors.


Believed to originate from Japan.

Government action

Fisheries and Oceans Canada is studying the Pancake Batter Tunicate population to improve its understanding of how it reacts and adapts to Canadian conditions.

For further information


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