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Styela clava
Club Tunicate
Tunicates Home | Ciona savignyi | Styela clava | Didemnum
Report a sighting to WDFW: (360) 902-2700
Don't forget to report it on your survey form too!

Where is it found?

Styela clava seems to like the calm, sheltered waters of marinas and grows rapidly under docks and on 'slip queens' - boats who sit unused for months at a time. Pleasant Harbor Marina on Hood Canal has a large infestation of Styela clava, as does Blaine Marina in Northern Washington. They breed rapidly in water temperatures above 60°F, 15 degrees C and form highly dense populations that overtake and crowd out other forms of marine life. The club tunicate (Styela clava) is native to Korea and Japan.


Styela clava, showing the stalk it uses to attach to hard surfaces.
Pleasant Harbor Marina dock.
- Photo by Janna Nichols

What is being done?

Washington State allocated funds in 2006 to help control populations and prevent the spread of this tunicate from one harbor to another. Commercial divers were hired to go pluck the tunicates from under docks and boats and dispense with the remains in landfills far from marine waters. Harbormasters in all Washington marinas were on the lookout for them on boats hauled out for cleaning.

What does Styela clava look like?

Styela clava can be about 5-6" long, with leathery, bumpy brown-to-rust colored bodies. Their siphons are smooth, with alternating dark/light bands around the edges. They have a thin stalk that attaches to a hard surface like a boat hull or a dock. Both siphons are erect. It often grows hanging down from the underside of docks and boats.


Styela clava showing alternating dark/light bands around siphons,
and bumpy surface of the tunic. Pleasant Harbor Marina dock
- Photo by Janna Nichols


Styela clava fouling the propeller of an unused boat
in Pleasant Harbor Marina.
- Photo by Georgia Arrow

Are there native species that could be mistaken for it?

There are several species that look similar:

  • Peanut Sea Squirt (Styela gibbsii) - shorter, has a uniform trunk width, no stalk, no banding around siphons

  • Stalked Hairy Sea Squirt (Boltenia villosa) - shaped more like Mickey Mouse with whiskers! Does have alternating bands around the siphons, but the little hairs make this tunicate distinctive.

  • Monterey Stalked Sea Squirt (Styela montereyensis) - Much longer stalk, found in high current areas, solitary, longitudinal ridges running the length of the body, one siphon flopped to the side like a dog's ear.

More photos of invasive tunicates are on this website

For more information about Styela clava, visit these websites:

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Tunicates Home | Ciona savignyi | Styela clava | Didemnum
Report a sighting to WDFW: (360) 902-2700
Don't forget to report it on your survey form too!