Geoduck Studies
Washington Sea Grant Coordinates Effort to Understand What's at Stake
By David G. Gordon
The pros and cons of geoduck farming have become topics of heated debate among shellfish growers and shoreline property owners in the Pacific Northwest. Both sides point to the lack of information about the effects of geoduck aquaculture on intertidal areas. In response, the Washington State Legislature recently asked Washington Sea Grant to gather information on geoduck farming, on which future decisions about the management of onbottom shellfish aquaculture activities can be based.
As requested by the State Legislature, WSG will review existing scientific information on geoduck farming. “We will be contracting researchers to compile all the relevant literature on geoduck aquaculture in the Pacific Northwest and also for items about on-bottom aquaculture for other types of shellfish, where applicable,” says Raechel Waters, WSG’s Associate Director. “It is our goal to assemble a base of information to help identify and evaluate any data gaps and information needs, which, in turn, will aid us in determining areas where additional research may be needed.”
The Legislature has also asked WSG to select and manage scientific research contracts for the purpose of assessing the effects of geoduck aquaculture on the Puget Sound and Strait of Juan de Fuca environments. The research will examine key uncertainties relating to the ecosystem and community effects of geoduck aquaculture and its implications for the health of existing wild geoduck populations.
The geoduck is North America’s largest burrowing clam. Individuals can attain a shell length of 10 inches and weigh in at an average of one to three pounds, with an occasional specimen reaching a 15-pound heft. The most distinctive feature of this bivalve is its siphon, which can extend about three feet, enabling this animal to survive at what is known as a “refuge depth,” far below the seafloor’s surface, beyond the reach of most shellfish predators.
Geoducks are long-lived animals, capable of surviving in the wild for 150 years or more. They are broadcast spawners and a female may produce about five billion eggs in its lifetime. (In compassion, a human female produces about 500 eggs in her lifetime). With such fecundity and few predators, it’s no wonder that wild geoducks are so abundant in Puget Sound. The Sound’s geoduck population is currently estimated at 674 million pounds, of which approximately 163 million pounds are available for commercial harvest.
Commercial harvesting of geoducks from the wild began in the early 1970s and continues to this day. Until fairly recently, clams in this fishery were gathered from the wild, solely by scuba divers equipped with high-pressure water hoses to blast the deep-burrowing clams from the subtidal sediments. Geoducks imported to Asia can fetch prices of up to $30 per pound, fueling a market currently estimated at around $80 million annually in Washington and British Columbia.
Over the past decade, the harvest of wild geoducks has been augmented by geoduck aquaculture in intertidal areas. By planting geoduck seed from hatchery sources, shellfish farmers can produce market-sized geoducks in about four to seven years. Washington’s geoduck farms are presently producing about 875,000 pounds of the clams per year. That compares to about four million pounds of wild geoducks harvested from submerged tidelands each year. Totaled, the two figures account for nearly half the world’s supply of geoduck meat.
Several potentially significant effects of geoduck aquaculture warrant close attention, according to WSG-funded researcher Carolyn Friedman, an associate professor with the University of Washington’s School of Aquatic & Fishery Sciences. One of these pertains to the production of geoduck seed for large-scale plantings. Over-dependence on a single hatchery broodstock could reduce the genetic diversity among wild populations. That might make the state’s geoducks less resistant to certain shellfish diseases and less adaptable to the range of conditions in Puget Sound and the Strait, Friedman says.
A second consideration is the effect of geoduck farming on intertidal and subtidal communities of animals and plants. Today’s geoduck farmers use short segments of PVC pipe and plastic netting to exclude clam-eating predators during the young geoducks’ initial years of growth. Whether the pipes and netting are altering the composition of eelgrass beds and other important nearshore habitats has yet to be determined, says Friedman.
The third topic of concern is centered around any possible damage to the intertidal habitat caused by the harvesting of farmed geoducks, including the removal of pipes and netting. Populations of aquatic plants, as well as marine worms, crustaceans, bivalves and other sediment-dwelling creatures, could be adversely affected by the disturbance to their habitats. Whether natural recruitment by populations outside of the acreage being farmed could offset any damage has yet to be determined.
“That’s why we need to gather and study additional data,” says Waters. “There’s been a tremendous surge in interest in geoduck aquaculture, but we just don’t have enough information to assess the potential benefits and drawbacks to the ecosystem, or if there are measures that can be easily taken to offset any disruption of the natural systems in Puget Sound.”
In conjunction with the data-gathering phase of the project, WSG will host a workshop this fall on the state of our understanding, focusing specifically geoduck harvesting. The workshop will draw on the expertise of national and international authorities. Their input will help others identify informational gaps and help set priorities for future WSG-funded research. One of several tangible products from this workshop will be a briefing document, summarizing the information presented at this event.
Following the workshop, WSG will solicit proposals for a series of research projects, intended to examine key uncertainties relating to the ecosystem and community effects of geoduck aquaculture and its implications for the health of existing wild geoduck populations. The State Legislature has identified an assortment of topics that warrant further scientific scrutiny, including possible impacts of the use of sterile triploid geoducks, similar to the so-called “sexless” oysters created in the mid-1980s by researchers at the University of Washington. Other research efforts could focus on geoduck parasites and diseases, impacts from geoduck harvesting, and the extent to which farmed geoducks alter the ecological characteristics of overlying waters while the tracts are submerged at low tide.
“Ours is the logical program to coordinate the research and disseminate key findings among the people who need it,” offers Waters. Indeed, WSG-supported research was instrumental in the development of the triploid oyster — a hatchery creation that today accounts for roughly one-third of all canned and jarred oysters sold in the state. In the early 1980s, WSG research and outreach efforts were important in establishing Washington’s Manila clam industry (see related story on Page 4). More recently, WSG-initiated research in geoduck clam genetics is providing insights into the management of wild and cultured stocks of these economically important bivalves. Several research projects on shellfish biology, ecology and disease are now under way.
WSG Water Quality Specialist Teri King has also facilitated and coordinated three State of the Oyster shellfish sampling events for waterfront property owners to determine the levels of pathogens in shellfish from their beaches. To protect shellfish operations from the effects of oil and chemical spills, WSG’s Oil Spill Prevention Education Specialist, Eric Olsson, assisted in planning and presenting an in-depth HAZMAT course for local shellfish growers. In addition, the program’s communications and outreach efforts have directly impacted Washington’s shellfish industry. Small-Scale Clam Farming for Pleasure and Profit and Heaven on the Half Shell: The Story of the Northwest’s Love Affair with the Oyster are considered the definitive works in their fields.
“We’re optimistic that Washington Sea Grant can help to resolve the geoduck controversy,” says the program’s Director, Penny Dalton. “In the past, we’ve demonstrated our commitment to marine habitat protection and to sustainable use of ocean resources. Our goal is to ensure that people understand geoduck issues and that good scientific information is available to manage geoduck aquaculture.”
July 2007
Contact David G. Gordon, Science Writer for Washington Sea Grant, for further information.