Squaxin Island Tribe Looking At Invading Oyster Drills

SQUAXIN ISLAND (April 28, 2003) — When Pacific oysters where introduced into Puget Sound in the 1930s, they brought with them an unwanted hitchhiker: the Japanese oyster drill (Ceratostoma inornatum). The snail eats oysters after boring through their shells, devastating some Olympia oyster populations. They may also prove to be a major barrier in the reestablishment of the Olympia.

The Squaxin Island Tribe is now exploring ways to exterminate Japanese oyster drills in the southern Puget Sound. “The biggest obstacle we’ve faced trying to reestablish Olympia oysters has been drills,” said Brian Allen, shellfish biologist with the Squaxin Island Tribe. “We saw a huge jump in the oyster drill population on Squaxin Island soon after we planted Olympia oyster seed a few years ago. Japanese oyster drills, because they have adapted to boring through the thicker shell of the Pacific oyster, have a much easier time with the smaller Olympias.”

“Olympia oysters took advantage of our pristine bays and beaches for centuries, growing and evolving into an important food source,” said Jim Peters, natural resources director for the tribe. “With human influence on the Olympia’s habitat, they have almost disappeared. It is our job to restore them to their historic abundance.”

One of the options the tribe is considering is using the oyster drill’s own life history against it. Tribal crews would collect the drills during their breeding stage, when they are at their most vulnerable. “Oyster drills congregate from early spring to early summer to spawn,” said Allen. “This makes it fairly easy to go out to the beach and simply remove them from the oyster beds. We just need to be out on the island when they’re coming together so we can get as many as possible.”

Also, since the drills can’t themselves migrate long distances, another way to control their spread is to set up quarantine or “drill free” zones. All oysters brought into a “drill free” zone would be checked to make sure they don’t carry drills. Most of the drill free zones in Washington are in Hood Canal. “Hopefully, Squaxin Island can become one of the few drill free zones in southern Puget Sound,” said Allen. “Having an area without drills would be a big advantage in restoring Olympia oyster populations.” The Squaxin Island Tribe has been collaborating with the Puget Sound Restoration Fund for the last few years to restore Olympia oysters on Squaxin Island. The tribe and the non-profit have spread thousands of oyster seed on the Island.

Over harvest and the water quality problems associated with timber processing initially caused the decline of Olympia oysters in the early 1900s. But introduction of Pacific oysters in the 1930s, and consequently the Japanese oyster drill, has kept Olympia populations low. “The drills came to Puget Sound on the shells of Pacific oysters and the kelp used to pack them,” said Allen. “In Asia, the Japanese drill populations were kept in check by the coevolving Pacific oyster which would put more of its energy into thicker shell development. The Japanese drills are more voracious than our native welk, or drill, which feed mostly on barnacles.” In some studies, Japanese oyster drills caused up to 90 percent mortality on some Olympia oyster beds.

“Olympia oysters have always been a central part of our culture and economy,” said Peters. “We are working to restore Olympia oysters not just of the sake of restoring a scarce species, but also for the sake of restoring an important part of our lives.”


For more information, contact: Brian Allen, Shellfish Biologist, Squaxin Island Tribe, (360) 432-3816, [email protected]. Emmett O’Connell, information officer, NWIFC, (360) 438-1181, ext. 392, [email protected]

Photos available: Oyster drills being collected for sampling at Squaxin Island. Can be e-mailed at high resolution.

Olympia Oyster Fast Facts

  • Scientific name: Ostrea lurida, which literally means “pale oyster”.
  • The Olympia oyster is very small; the shell is approximately the size of a 50 cent piece. They also grow slowly, reaching their full size in about three years.
  • Legend has it that the origin of the “Hangtown Fry” is when a condemned man in San Francisco was asked what he would like for his last meal, requested the two most expensive foods in town: Olympia oysters and eggs.
  • Olympia oysters range from southeast Alaska to the Baja Peninsula in Mexico, but historically were most concentrated in coastal Washington.
  • The commercial harvest of Olympias started in the 1850s when 10,000 bushels were harvested annually and peaked in 1890s with 130,00 bushels.
  • The Olympia oyster is Washington State’s only native oyster.