Intertidal Shellfish Culture in the Pacific Northwest: A Summary of Current Culture Practices, Production Estimates for Oysters and Clams and a Focus on Geoduck Culture Techniques and Production
Jonathan P. Davis, Taylor Shellfish Farms, Inc.
Shellfish aquaculture in the Pacific Northwest relies on a combination of highly productive marine and estuarine environments, satisfactory water quality, an innovation-driven technological base and an available work force to farm the tidelands. Pacific oyster production is the predominant species cultured in the four-state region (California, Oregon, Washington, and Alaska) with 94.2 million lbs. ($84.8 million) harvested annually. Of this total, the majority is grown on-bottom and harvested by hand or dredge for the shucked market, and the remainder is grown on-bottom or in cage culture for half-shell raw markets. Manila clam production (8.5 million lbs., $17.1 million) is the second most valuable farmed mollusk in the region. Culture methods rely mainly on natural production enhanced with hatchery-produced seed and intensive culture utilizing exclusively hatchery derived seed for growout under netting or in cages. Harvesting is done almost exclusively by hand with some limited mechanical methods in use currently.
Geoduck production constitutes the third major species cultured in the intertidal regions with 0.85 million lbs ($5.31 million) grown on approximately 150 acres in Washington State. Geoduck culture is practiced in the lower intertidal (generally –2.0’ to about +1’ below MLLW). Culture methods rely on PVC tube sections inserted into sand flat beaches although alternative culture methods including plastic mesh “tents,” direct seeding beneath predator netting, or vexar mesh tubes are also being used. Predator netting is generally removed after 12 months, as are tubes in many cases, depending upon the site and suite of predators present. Geoducks grow for 3-5 additional years prior to harvest at >1.5 lbs. Harvesting is done by hand using pumps and pressurized water jets that loosen the substrate around individual geoducks prior to extraction. Yields of geoduck are generally in the range of 50,000–60,000 lbs. per acre. Constraints to expanded geoduck culture include suitable intertidal sites and supply of seed.