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Pacific Oyster

Crassostrea gigas

Illustration of a Pacific Oyster

Also Known As

  • Japanese oyster
  • Miyagi oyster
  • Pacific cupped oyster

U.S. farmed Pacific oysters are a smart seafood choice because they are sustainably grown and harvested under U.S. state and federal regulations.

Environmental Impact

Oysters provide net environmental benefits by removing excess nutrients and improving water quality.

Feeds

Growing oysters require no feed – they filter phytoplankton directly from the water column.

Farming Methods

Oysters are grown in tidal areas. They can be grown directly on the beach bottom or in mesh bags, trays or cages that are either anchored in the water column or floated on rafts.

Human Health

Shellfish toxins and bacteria occur naturally in the environment and can cause food-borne illnesses. State and federal regulations require monitoring of farmed oysters to ensure they are safe to eat.

  • Availability

    Available year-round.

  • Source

    Estuaries, mostly in the Pacific Northwest.

  • Taste

    Ranges from sweet to briny.

  • Health Benefits

    Oysters are low in saturated fat and excellent sources of omega-3 fatty acids and iron.

U.S. Farming

Management

  • Permitting for shellfish aquaculture is governed by federal, state and local governments.
  • The federal agencies involved are NOAA, the Army Corps of Engineers, U.S. Fish & Wildlife Service, U.S. Department of Agriculture, the Environmental Protection Agency, the Food and Drug Administration, the Bureau of Ocean Energy Management, and the Coast Guard.
  • Shellfish farms must adhere to federal regulations including those in the Magnuson-Stevens Fishery Conservation & Management Act, the Endangered Species Act, the National Environmental Policy Act and the Clean Water Act.
  • Information on shellfish aquaculture permitting can be found in the Shellfish Growers Guide.
  • A variety of shellfish aquaculture tools, including maps and models, are available to coastal managers.

Farming Methods

  • Juvenile oyster (seed) production:
    • Oyster larvae are bred in hatcheries and fed a diet of algae for 2-3 weeks.
    • Larvae then attach to a provided substrate, usually old oyster shells.
    • Settled larvae are transported to grow-out sites in coastal waters.
  • Mature oyster grow-out:
    • On-bottom – directly on the beach bottom in tidal areas.
    • Off-bottom – in racks, mesh bags or cages that are submerged and attached to anchored frames in the intertidal zone.
    • Suspended culture – bags or cages are attached to rafts and floated in the tidal zone.

Production

  • In 2012 the United States produced 35 million pounds of oysters (including Pacific oysters), valued at $136 million.

The Science

Environmental Considerations

  • Habitat:
    • Oyster farming has a benign ecological footprint, with little disturbance of sediments or aquatic vegetation during grow-out.
    • Some oyster harvesting methods involve dredging, but long-term effects on the environment are rare.
  • Feeds:
    • Once past the larval stage, oysters do not need to be fed because they filter their food from the water column.
  • Genetics:
    • The Pacific oyster is native to Japan, so there is some concern about the species outcompeting native oysters. However, this has not been an issue in the United States.

Ecosystem Services‎

  • Water quality improvements:
    • Oysters are filter-feeders, removing algae, organic matter and excess nutrients from the water column as they grow and improving water quality.
    • When oysters are harvested, excess nutrients, such as nitrogen and phosphorus, are removed from the ecosystem.
  • Providing habitat:
    • Oysters and the gear used to farm oysters provide habitat for marine organisms.
    • Oyster beds stabilize coastal sediments and help minimize impacts from storm surges.

Human Health

  • Shellfish toxins:
    • Shellfish poisoning is an illness that can occur from eating contaminated shellfish.
    • Shellfish can assimilate the toxins that cause shellfish poisoning from the algae on which they feed.
    • Early warning systems exist to detect harmful algal blooms that produce toxins.
    • New technologies, such as the Environmental Sample Processor, provide near real-time detection of harmful algal species.
    • For more information on identification, prevention and monitoring of harmful algal blooms, read about the NOAA Ocean Service Harmful Algal Bloom programs.
  • Pathogenic bacteria:
    • The bacteria Vicbrio parahaemolyticus (Vp) and Vibrio vulnificus (Vv) occur naturally in the environment and can cause food-borne illness from consuming raw shellfish.
    • Ingestion of undercooked or raw shellfish with Vp or Vv can lead to gastrointestinal illness.
  • Public health officials monitor shellfish from growing areas to ensure they are save to eat.

Physical Description

  • Can reach up to 10 inches in length.
  • The shell is elongated, thick, rough and sometimes sharp. The inside of the shell is white to off/white with purple streaks.
  • The shell has a “cupped” shape to it, giving rise to its alternate name “Pacific cupped oyster.”

Biology

  • Are of the shellfish family. Like mussels, clams and scallops they are bivalve mollusks, and have a hinged shell.
  • Adults are sessile – they stay in one place – and inhabit both intertidal and sub-tidal areas.
  • Have fast growth rates and high reproduction rates.
  • First mature as males, then later develop female reproductive capabilities.
  • Each female can produce between 50 and 200 million eggs during a spawning event.

Research

Last updated: 07/31/2015