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University of California
California Aquatic Invasive Species (AIS)
Invasive Seaweeds and Hull Fouling Species
Spirorbis spp. - Visit ITIS for full scientific classification.
- Common in lower intertidal, and shallow subtidal areas.
- Spiral tubes encrust submerged vegetation including the blades of giant kelp (Macrocystis pyrifera) along the California coast.
- Also found settled on rocks, pier pilings, vessel hulls, shells of other animals, etc.
Invasion Pathways and Distribution
- Spread by attaching to vessel hulls, from which larvae swim to settle on surfaces in marinas
- Found worldwide, including throughout California.
- Native range is unknown.
- Filter-feeder, uses feather-like gill tentacles to capture particles in the water.
- Reproduce sexually by releasing sperm and eggs into the water, where they unite to form swimming larvae.
- The chalky tubes form crusts on boat hulls.
- This fouling growth roughens the hull’s surface, creating friction or “drag” that slows sailboats and increases fuel consumption for powerboats.
- Tolerant of copper in antifouling paint, and very difficult to remove.
References and Useful Links
For references by category and links to other useful AIS sites see our LEARN MORE page.
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