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In the News

August 8, 2006

What a difference a day makes—abalone pest is in the dunk tank

University of California, Davis, biologists have found a way to nearly eliminate an invasive pest in California abalone production and display facilities.

   Farmed red abalone. The one on the right is severe sabellid infestation with vertical shell growth and deformed respiratory pores.

Farmed red abalone. The one on the right is severe sabellid infestation with vertical shell growth and deformed respiratory pores.
Photo by Thea Robbins

The shell-dwelling fan worms (a sabellid polychaete) originated in South Africa and deform and reduce the marketability of abalone. The worms settle on the shells of abalones and other gastropods, which are a kind of sea snail, inhibiting and grossly deforming shell growth. Several native intertidal snails and slugs are susceptible to fan worm infestation.

The parasitic polychaete is a member of a group collectively known as sabellids or "fan worms." With funding from the UC Exotic/Invasive Pests and Diseases Research Program, Ecologist Ted Grosholz from Environmental Science and Policy, and James Moore, Medicine and Epidemiology, Veterinary Medicine, at UC Davis, found that submerging the fan worm in fresh water for 24 hours can destroy it. This practice allows abalone culture and aquarium operators to destroy the fan worms in abalone holding units.

“The pest doesn’t affect the abalone's meat, but damages the shell so much that the abalone’s growth slows or virtually stops,” says Grosholz.  “Though the industry has learned to manage the pest, concerns over its impact and its potential spread have become widespread.”

After sampling studies in 20 California locations that are known to, or may have been, exposed to sabellid-infested abalone, Moore and Grosholz found that sabellids have not become established in intertidal gastropod populations anywhere in California.

Abalone is highly prized in many cultures and is considered a delicacy in certain parts of Asia, especially in China and Japan. The inner shell of abalone has an iridescent green, blue, or pink sheen, which is a source of mother-of-pearl. 

Because of its popularity, abalone has been depleted in many locations, including the coast of California. These declines, coupled with the value of abalone meat on the world market, have promoted the concept of abalone aquaculture internationally to supplement the world supply of abalone. Facilities free of fan worms are advised to not obtain abalone for stocking from facilities where this pest has been observed.

This research provides resource managers information on whether fan worm infestations are present among native intertidal snail populations. “Our sabellid transmission studies demonstrate that infestations can be sustained in a variety of sea snails, so the threat of such infestations becoming established in a particular location is real,” says Moore.

“We recommend a 24-hour minimum fresh water immersion exposure time to destroy all life stages of the sabellid polychaete,” says Moore. “This amount of time is recommended for field applications such as sanitizing a production tank after one group of abalone is moved out and before another is moved in.”

The research team found that transmission of fan worms from one turban snail to another could occur, although the rate of transmission is very much lower than the rate between abalone. Turban snails can support fan worm infestations although they are less susceptible than abalone.

In a separate series of experiments, Moore’s research team found the minimum fresh water exposure time necessary to kill mobile fan worm larvae is one minute. Using a biocide such as chlorine is recommended to sanitize hands and tools when working in different production areas or display tanks.

The Davis group developed a DVD describing the polychaete, the threat it poses and recommended techniques for preventing sabellid acquisition and transmission. The DVD will be distributed to all abalone culturists and display facilities and contains both English and Spanish versions.


High-resolution image (356KB) "Farmed red abalone. The one on the right is severe sabellid infestation with vertical shell growth and deformed respiratory pores." Photo credit: Courtesy of UC Statewide IPM Program, Thea Robbins. Photos are for use with this release only. All other uses see Legal Notices.

The Grosholz Lab


Stephanie Klunk, Communications Specialist
UC Statewide IPM Program
(530) 754-6724

Dr. James Moore
Bodega Marine Laboratory
Phone 707-875-2067

Ted Grosholz, Ecologist
Environmental Science and Policy
UC Davis 
(530) 752-9151

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