Puget Sound Shoreline, Rae A. McNally

Many tunicates look like exotic underwater plants, but they are actually a group of marine animals. Tunicates—also called sea squirts—are shaped like blobs or tubes, with two siphons on the top and an outer covering called a tunic. Tunicate species either live alone or in colonies. Solitary tunicates can get to six inches in length. Tunicates that live in colonies can spread over large areas ranging from a few square feet to acres.  

Puget Sound is also home to many native species of tunicates that are not a problem.

What’s the problem?

Three species of non-native tunicates have the potential to harm important habitat in Puget Sound by crowding out native species. Left unchecked, these invaders could cause serious economic damage to the critical habitat that forage and commercial species depend on. They could also affect important geoduck growing areas as well as other aquaculture operations.  


Where are tunicates in the Puget Sound region?

Club tunicate. Two marinas in the Pacific Northwest have infestations of club tunicates:

  • Pleasant Harbor and Home Port marinas, south of Brinnon in Hood Canal
  • Blaine and Semiahmoo marinas in Drayton Harbor , Whatcom County  

Transparent Ciona tunicate. First detected in March 2004, Ciona range throughout the lower portion of Hood Canal. These tunicates form dense mats and crowd out other species. Extreme low dissolved oxygen events in September 2006 didn’t seem to adversely affect this tenacious tunicate.

Invasive Didemnum. Found in several locations around the Sound including Dabob Bay , Liberty Bay , Edmonds Underwater Park , and the Shilshole and Des Moines marinas.


How did invasive tunicates get to Puget Sound?  

Club tunicate. Native to Asia . Probably introduced in discharged ballast water or as hitchhikers on ship hulls.

Transparent Ciona tunicate. Native to Japan . Probably introduced in discharged ballast water or arrived as hitchhikers on hulls of ships.

Invasive Didemnum. Probably introduced with oysters or other shellfish stock and in discharged ballast water or arrived as hitchhikers on hulls of ships.


What’s being done in Puget Sound?  

In 2006, Gov. Gregoire and the Washington State Legislature provided emergency and supplemental funds to eradicate invasive non-native tunicates. Key results expected from this funding:

  • Progress report to the Legislature of status, progress and challenges for controlling and eradicating invasive tunicates.
    Status: Done
  • Eradicate all invasive club tunicates.
    Status: Commercial divers on contract to Department of Fish and Wildlife removed club tunicates from all boats in infested waters. More work needs to be done to remove these animals from marina floats, pilings and other in-water structures.
  • Develop a management plan for invasive transparent Ciona savignyi tunicates.
    Status: State partners will develop a management plan for transparent tunicates in 2007-2008. 
  • Develop educational materials to minimize the spread of invaders by recreational boats.
    Status: The Puget Sound Partnership produced and distributed thousands of club tunicate identification cards to boat owners at marinas, created an invasive tunicate Web page to report sightings of these animals and hired Pacific Northwest Scuba to train dive clubs how to identify tunicates and what to do once they are discovered. 
  • Survey populations of transparent Ciona tunicate.
    In May 2006, Washington Department of Natural Resources (DNR) contracted with the Skokomish Tribe to survey the lower Hood Canal region. DNR will use the results of the survey to work with various groups to develop a plan for eradicating this invasive species.



Fish and Wildlife hired commercial divers to remove infestations of club tunicates in 2006. Divers removed more than 90 pounds from almost all of the infested boats in four marinas. In addition, they surveyed about 30,000 square meters of docks in the infested marinas, cleaned about 33 percent of the area and removed about 2,000 pounds of invasive tunicates from the marina structure. The state needs to do more work to remove the remaining tunicates in these infested marinas. Members of the Washington Scuba Alliance (WSA) and the Reef Environmental Education Foundation (REEF) gathered on Oct.25, 2006 at Sund Rock in Hood Canal near Hoodsport to remove the invasive tunicate Ciona savignyi. The dive teams surveyed, took photographs and videos and removed most of the animals they found.
>> Report and Photos of Ciona savignyi Removal Sund Rock North Wall, Hood Canal

Invasive Didemnum. Recreational divers under the guidance of the Edmonds Underwater Park docent took aggressive action to remove all known patches in the underwater park. They buried colonies, wrapped in them plastic and covered them in sheeting and introduced salt or chlorine tablets to get rid of them. The volunteers hauled out infested buoys and anchor lines onto the beach where the animals died. This successful undertaking has effectively left the underwater park free from Didemnum.

 >> Learn more

For more information about the Puget Sound Partnership's Aquatic Nuisance Species Program, contact Kevin Anderson, 360.725.5452.




Distribution of invasive tunicates in Puget Sound.
Distribution of invasive tunicates in Puget Sound.