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clean up effort

Progress Updates

Styela clava

Didemnum sp.

Ciona savignyi

Scuba Alliance














Invasive Tunicates in Washington State

WDFW: 360-902-2700

Styela clava or Club tunicate

Styela clava under the docks at Pleasant Harbor Marina

photo by Charlie Waters

  • State researchers and biologists have identified that a non-native species of sea squirt, the club tunicate, in the Blaine and Pleasant Harbor marinas.
  • The club tunicate is native to Korea and Japan, and has no natural predators in this part of the world. This invasive species of sea squirts has the potential to spread rapidly through the Sound.
  • The animals can reach nearly 9 inches in length. Club tunicates foul boat hulls, marina equipment and shellfish growing equipment.
  • Club tunicates can grow in extremely high densities crowding out other marine species such as shellfish.
  • This invasive species out-competes native organisms for space and food. The club tunicate can grow in extremely high densities and crowd out other marine species and habitat- including shellfish growing areas.
  • So far, club tunicates only have been found in the three marinas.
  • However, their breeding season coincides with the start of boating season. Club tunicates usually begin breeding in June when water temperatures warm up. Boaters can unwittingly spread this alien species to other locations.
  • This is why the state is taking action now.
  • In January, Gov. Chris Gregoire gave the Washington Department of Fish & Wildlife $75,000 to survey and kill infestations of club tunicates, and to conduct research on another invasive variety of tunicates.
  • The public should call WDFW: 360-902-2700 to report club tunicates on their boats, docks, or in water equipment

Report your sighting to WDFW: 360-902-2700

Styela clava on buoys and mussel lines - Prince Edward Island

More information:

Styela clava is a solitary tunicate, meaning that each individual adheres separately to a substrate. It is native to the N.W. Pacific: Japan, Korea, N. China and Siberia. They have spread to NW Europe, North America, Australia and New Zealand. They reproduce throughout most of the year as long as the water temperature is not below 15 degrees Celsius, and reach densities of up to 500-1500 per square meter. They prefer relatively shallow water and attach to hard substrates. Styela clava competes for space and food with native and aquaculture species, and fouls marine farming equipment, vessel hulls, and other structures. No natural predators have been identified to date.

Presently there are three confirmed populations in Washington - Pleasant Harbor Marina in Hood Canal, Neah Bay Marina, and Blaine Marina. It is also present at numerous locations in S. British Columbia, mostly at marinas, but also at some aquaculture sites.

Hand removal is considered to be the most reliable control method, but it is costly and time consuming. An effort was made to remove the tunicates from the boat slips at Pleasant Harbor Marina in November of 2005. Approximately 30 divers worked for two hours removing as many tunicates as possible by hand. The Marina has approximately 270 slips. Divers were able to clean a little more than two of the slips - or approximately 1% of the infestation - filling the bed of a full-size long-bed pickup truck. The majority of the boats at the marina have tunicates on the hulls. The potential is very high for them to be spread throughout the region if a control mechanism is not identified prior to the onset of boating season. Other methods to be considered include exposure to air and/or extreme temperatures, and sprays or dips of high salt, hydrated lime, or acetic acid solutions.

For more information on invasive tunicates, please go to the PNW Scuba website: www.pnwscuba.com/critterwatchers/invasive.htm

Report your sighting to WDFW: 360-902-2700

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