Ancient Oysters Could Help Restore Native Populations

OLYMPIA (June 17, 2004) – The Squaxin Island Tribe is looking at centuries-old oyster shells to find clues about what Olympia oysters looked like before they almost disappeared earlier this century.

“The size and character of these ancient Olympia oyster populations is a big mystery,” said Brian Allen, Squaxin Island tribal shellfish biologist. “Were Olympias a different size, were they shaped different? What can this tell us about natural oyster reef communities? These are important questions if we want to restore self-sustaining populations of Olympias.”

The oyster shells, which are between 500 and 1,000 years old, were found in a “midden” or a deposit of shells at an ancient site on Eld Inlet. A variety of environmental conditions, from timber mill effluent to competition from invasive species, as well as over-harvest severely depressed Olympia oyster populations. But, the tribe has been working in recent years to restore the native oyster.

“We have always depended on Olympia oysters,” said Jim Peters, the Squaxin Island Tribe’s natural resources director. “We now have a unique opportunity to look back in time to see what oysters were like and compare them with some populations we’re trying to recover.”

In addition to looking at how Olympias might have changed, the tribe is also ramping up its research of small Olympia populations on Squaxin Island. Tribal researchers are measuring Olympias and assessing their habitat. “This kind of baseline data, from water quality to things as simple as growth patterns on different beaches, is important when we’re thinking about restoration,” said Allen.

“Olympias used to be the single most important shellfish in our diet,” said Peters. “They used to be everywhere. We’re working to make them a major food source again.”

The tribe is also experimenting with “shell strings” to find out how and when Olympia oysters reproduce. Shell strings are hung like Christmas popcorn between the legs of small steel tripods with shells.

“Olympia oysters, unlike other oyster species, retain fertilized eggs in a brooding chamber for a few weeks until the young are released into the water,” said Allen. Larval oysters move with the tide until they settle on a hard surface, or “cultch.”

Allen suspects the type of cultch a juvenile oyster attaches itself to goes a long way to determining its success. Japanese Pacific oyster shell is a common cultch for oyster culture, but may not be the best choice for Olympias oysters. “Olympias evolved growing on Olympia oyster shells,” said Allen. “We think using either actual Olympia shells or something that is pretty close, will lead to greater success when attempting to restore oyster reefs.”

“Finding out how Olympias evolved and survived for centuries is one of the best ways we can restore them,” said Peters. “The more we know about Olympias the better we can ensure that the small populations of Olympias will continue their comeback.”


For more information, contact: Brian Allen, shellfish biologist, Squaxin Island Tribe (360) 432-3816. Jim Peters, natural resources director, Squaxin Island Tribe, (360) 432-3800. Emmett O’Connell, South Sound information officer, NWIFC, (360) 438-1181, ext. 392, [email protected].