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Oysters (farmed)

©B. Guild/ Charting Nature, www.chartingnature.com

HIGHLIGHTS

  • Most Eastern oysters in the market are wild, but a number of hatcheries now produce seeds for oyster farmers
  • On the west coast of North America, almost all oysters are farmed from seeds, which largely derive from non-native species

HEALTH ADVISORY

Oysters may carry the Vibrio vulnificus bacterium, a naturally occurring bacterium that is in highest concentrations in summer months, which can be fatal when consumed by people with compromised immune systems. Health officials recommend cooking oysters thoroughly to eliminate any harmful bacteria.  

Paralytic shellfish poisoning (PSP) is caused by eating bivalve shellfish contaminated with algae containing harmful toxins. The toxin that causes PSP cannot be destroyed by cooking or freezing.

A NOTE ABOUT
RED TIDE

Red tide is a naturally occurring phenomenon that is the result of a “bloom” of a species of microscopic plankton that produce toxins. Red tide may create a brownish-red sheen on the surface of the water, but can also be invisible. Shellfish such as oysters, clams and mussels that feed by filtering seawater can accumulate the toxins as they feed. Although the toxins do not kill the shellfish, contaminated shellfish are unsafe for human consumption and can cause a variety of health problems, including paralytic shellfish poisoning (PSP). Local and state government agencies are responsible for routine testing of shellfish beds and promptly close contaminated areas until the shellfish are safe for human consumption.

Two species of oysters dominate the U.S. supply: Eastern oysters and Pacific oysters.

The taste of oysters is strongly influenced by the characteristics of local waters, and species tend to be marketed by origin. Other species commonly found include the Olympia oyster, the Japanese Kumamoto oyster, and the European flat oyster. Oysters are the most commonly farmed shellfish in the world.

Eastern oyster (Crassostrea virginica): Fished and farmed from Atlantic Canada to the Gulf of Mexico, the Eastern represents about 80 percent of U.S. oyster production. Most are collected from the wild, but overfishing, habitat degradation, and disease have driven wild catch levels in some areas to record lows. Farmed Eastern oysters, grown using a rudimentary form of aquaculture where farmers transport oysters from nursery to grow-out areas, are considered a good environmental choice.

European (flat) oyster (Ostrea edulis): This species is sometimes called the Belon oyster, in reference to a once-major production area in France. Disease and pollution have decimated populations, and European production is a small fraction of what it once was. Small farming operations have introduced flat oysters to New England, California, and Washington State.

Kumamoto oyster (Crassostrea sikamea): Native to Kumamoto Bay, Japan, this small oyster was introduced to the west coast of North America after World War II. Today, they are farmed from British Columbia to northern California and are relatively expensive due to labor-intensive farming practices.

Olympia oyster (Ostrea lurida): The Olympia oyster is a very small oyster found from Alaska to Baja California, although Washington is the only state that produces Olympias on a commercial scale. Overfishing and pollution have reduced catch levels to less than one percent of former levels. A few growers in Washington State have had some success farming Olympias, but production remains limited.

Pacific oyster (Crassostrea gigas): Native to Asia, the Pacific comprises 98 percent of world farmed oyster production. The Pacific oyster is now farmed extensively in Washington State, British Columbia, Europe, and the Pacific Rim. Most growers use hatchery seeds and raise the oysters on the ocean bottom or on trays or ropes suspended in the water column.

CONSERVATION NOTES

Oysters are usually farmed in nets, trays, or racks suspended in the water column and are considered good environmental choices. Although farms may use non-native species and there are risks of introducing diseases, many of the environmental issues encountered with other forms of aquaculture are not problems with oyster farming. The oyster is a filter feeder—it filters plankton and may improve local water quality conditions. Farmed oysters do not require supplemental feed, so there is no net loss of wild fish as is the case with carnivorous fish farming. Oyster farming requires little or no chemical use. The collection of oysters by dredging the ocean bottom may be detrimental to seafloor habitat and associated organisms.

IN SEASON

Available year-round; periodic closure of some oyster beds may occur due to local water conditions.

PRODUCT FORM

FRESH:

  • Live
  • Meat

FROZEN:

  • Meat
  • Half shell

BUYING TIPS

  • If stored at 36-40 °F in a moist environment, oysters can be kept up to two weeks after they are collected; however, shelf life is shorter after spawning in the summer.
  • As a rule, Olympia oysters command the highest price, followed by European oysters, Kumamotos, Pacific oysters, and Eastern oysters.
  • By law, a live-oyster shipment must include identification of the oysters’ origin and collection date; it is illegal to discard this tag sooner than 90 days after delivery.

ASSOCIATIONS

Pacific Coast Shellfish Growers Association
120 State Ave. NE, PMB #142, Olympia, WA 98501, Phone: 360–754–2744, Web Site: www.pcsga.org, Executive Director: Robin Downey • The largest shellfish association in North America representing the interests of shellfish growers from British Columbia, Alaska, Washington State, Oregon, California, Mexico, and Hawaii. The PCSGA is a good source of information about environmental issues, shellfish safety and health issues, technological advances, marketing and research.

British Columbia Shellfish Growers Association
350 (B) Robson Street, Nanaimo, BC V9R 2V5 Canada, Phone: 250–714–0804, Web Site: www.bcsga.ca, Executive Director: Pamela Parker • Represents scallop, clam, and oyster growers in the province.

East Coast Shellfish Growers Association
1623 Whitesville Road, Toms River, NJ 08755, Phone: 732–349–1152, Web Site: www.ecsga.org• A relatively small association representing oyster and mussel growers. Its web site provides links to a number of nongovernmental associations.