About the Species
The Eastern oyster is treasured as food by humans and other species. They are habitat for fish, crabs, and other critters—and because as filter feeders, they help filter the water. Centuries ago, they were plentiful. In some places, reefs were so big that ships had to navigate around them. Since then, in many areas, the populations have dwindled to just a few percent of what they once were. This is due to disease, overharvesting, habitat loss, and poor water quality.
But people—including NOAA scientists—are working hard to rebuild oyster populations. Many people are growing oysters for people to eat. Oyster aquaculture—farming of these tasty shellfish—is a growing industry. And NOAA and our partners are working to restore the healthy oyster reefs that so many other species rely on for habitat. Recreational anglers target healthy reefs for fishing opportunities, too. In the Chesapeake Bay, for example, NOAA and partners are involved in the world’s largest oyster restoration effort. There, they have restored nearly 1,100 acres of oyster reef.
- Reaches 8 inches at maturity.
- The shell has smooth edges and is oval in shape. The inside of the shell is white to off/white to brownish in color.
- The shell has a “cupped” shape to it, giving rise to its alternate name “American cupped oyster.”
- 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 subtidal areas.
- Have fast growth rates and high reproduction rates.
- First mature as males, then later develop female reproductive capabilities.
- Each female can produce over 100 million eggs during a spawning event.
Where They Live
- Eastern oysters are found along eastern North America from the Gulf of St. Lawrence to the Gulf of Mexico. They are found in the middle and lower Chesapeake Bay and its rivers. They are the only species of oyster native to this region.
- Eastern oysters live in brackish and salty waters from 8–35 feet deep. In some warmer areas, they are able to live in the intertidal zone. They attach to firm bottom areas and to each other to grow into reefs. These reefs provide habitat for fish, crabs, invertebrates, macrofauna, and birds.
Oyster Management and Restoration
Middens—historic piles of oyster shells discarded after humans ate the meat—show that people have eaten Eastern oysters along the East Coast of North America for perhaps 2,000 years or more. For people who enjoy eating them, they are a treasured culinary delicacy.
But their status as a tasty source of protein, vitamins, and minerals led to years of overharvesting. Oysters also face challenges from disease and habitat degradation. Today, in many areas, oyster populations are only a fraction of what they once were. In the Chesapeake Bay, scientists estimate that the population is only at 1–2 percent of historic levels.
NOAA is teaming up with other organizations to restore oyster reefs up and down the East Coast. In the Chesapeake Bay, we are part of the world’s largest oyster restoration effort. With partners, we are working to restore oyster reefs in 10 Chesapeake Bay tributaries by 2025. That’s the goal set by Chesapeake Bay Program. So far, three tributaries are considered restored, and work continues in seven more. All together, in Maryland and Virginia, roughly 1,100 acres can be considered restored as part of this effort.
We also support science related to Eastern oysters. Our scientists provide technical advice to people who are working on oyster restoration projects. And we carry out and fund research about oysters, too. A recently published report details the benefits that restored oyster reefs bring to the ecosystem, such as:
- Filtering the water
- Providing habitat for fish, crabs, invertebrates, and macrofauna
- Supporting commercial and recreational fishing
U.S. farmed Eastern oysters are a smart seafood choice because they are sustainably grown and harvested under U.S. state and federal regulations.
- 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.
- 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.
- 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.
- Once past the larval stage, oysters do not need to be fed because they filter their food from the water column.
- The Eastern oyster is grown in its native range, so there is some concern that farmed oysters could decrease genetic variability of wild populations. However, this has not been an issue in the United States.