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Ascidiella aspersa

  Scientific Name:

Ascidiella aspersa

 Common Name:

Euorpean sea squirt (others: dirty sea squirt, solitary ascidian)

 Native Range:


 Established Range:

On the East Coast, from the Bay of Fundy to Cape Hatteras

 Established in Rhode Island?

Yes, throughout Narragansett Bay

 Date and Location of Introduction:

1970's, New England

 Method of Introduction:

Unknown, but likely through hull fouling or ballast water


A. aspersa can be found in protected subtidal areas, attached to rocks, boulders, and artificial structures such as pilings, boat hulls, bouys, and floating docks. This tunicate can can tolerate a wide range of temperatures, and can survive in salinities between 18 and 40 parts per thousand. Prefers shallow waters and can only be found at depths less than 90 meters.


A. aspersa is a filter feeder that eats zooplankton, phytoplankton, and detritus.

 Average Life Span:

Approximately 18 months


A. aspersa is hermaphroditic and breeds by broadcast spawning from March to October in the New England region.


All invasive tunicates, including A. aspersa, pose the same problems. These tunicates are notorious fouling organisms, and can completely cover submerged boat hulls, aquaculture cages, and just about any other surface that they are capable of living on. As a result, they can slow down boats and have negative impacts on the local environment. Invasive tunicates have been known to smother shellfish and other sessile organisms, and will outcompete native filter feeders for food and space.


There are no known effective control methods at this time. Copper-based anti-foulants have little effect.

 Identification Card:

Courtesy of Salem Sound Coastwatch


 Works Cited:

ISSG. 2010. Ecology of Ascidiella aspersa. The Global Invasive Species Database,

NIMPIS. 2010. Ascidiella aspersa (soliatary ascidian). National Introduced Marine Pest Information System,