Oyster Reef Habitat
Oysters live in salty or brackish waters on all U.S. coasts, clustering on older shells, rock, piers, or any hard, submerged surface. They fuse together as they grow, forming rock-like reefs that provide habitat for other marine animals and plants.
Fresh oysters from Kachemak Bay oyster mariculture operations, Homer, Alaska.
The Value of Oyster Reef Habitat
Oysters begin life as free-floating spats—tiny, swimming clam-like creatures. Before long, they settle down and attach to a solid surface where they will grow for the rest of their lives. Rocks, old shells, wrecks, and piers accumulate oysters that grow together, shell upon shell. As the reef takes shape, it becomes excellent shelter for other sea life.
Oyster reefs create important habitat for hundreds of other marine species and filter and clean the surrounding water. Species like mussels, barnacles, and sea anemones settle on them, creating abundant food sources for commercially valuable fish species. Oyster reefs provide habitat to forage fish, invertebrates, and other shellfish. They also provide a safe nursery for commercially valuable species including:
Oysters are a crucial component of global ocean health, providing food, jobs, and habitat. Oyster reefs also provide important barriers to storms and tides, preventing erosion and protecting productive estuary waters.
Ongoing threats to oysters mean that, unless deliberate efforts are made to restore them, we are in danger of losing the benefits oyster reefs provide. When oyster reefs are only utilized for commercial oyster meat, they can become degraded. But when they are restored and managed as a sustainable resource, oyster reefs provide billions of dollars in value to the economy.
NOAA has identified oyster reef restoration as a conservation priority. We work with partners to restore native oysters and regain the critical ecosystem functions they provide across the United States.
Benefits of Oyster Reef Habitat
Oyster cultivation and harvest provide significant economic value to regional coastal communities. Farmed oysters, clams, and mussels account for about two-thirds of total U.S. marine aquaculture production. Oyster production in 2015 was worth $234 million, up substantially from $164 million in 2012.
Habitat for Other Species
The structure that oyster reefs create provide crevices that fish and crabs need to hide from predators. While they’re there, they can have a meal as well—the smaller organisms that fish and crabs like to eat grow on and near oyster reefs. Many of the species that spend time around oyster reefs are recreationally and commercially valuable.
Besides providing seafood, oysters make waters healthier. Since oysters feed by sifting algae from the water, they function as a natural filter and improve water that is overloaded with nutrients. A single oyster filters up to 50 gallons of water per day. The clearer, cleaner water supports plentiful underwater grasses, which—like the oyster reef—create a stable bay bottom and a safe, nurturing habitat for juvenile crabs, scallops, and fish.
Oyster reefs protect underwater vegetation and waterfront communities from waves, floods, and tides. Well-established eelgrass beds help stabilize the bottom, providing additional resilience against wave action. Healthy reefs and established vegetation protect valuable habitat, reduce wave energy preventing erosion, and fortify wetlands as a protective barrier.
Challenges for Oyster Reefs
In 1607, when Captain John Smith explored the Chesapeake Bay, there were oyster reefs so prominent they made the waters hazardous for ships. When Henry Hudson arrived in New York in 1609, the harbor’s oyster reefs were the largest source of oysters worldwide.
Today, oyster populations are at historic lows. Erosion from development, wetland loss, and excessive nutrient pollution have proved devastating for the shellfish, increasing likelihood of disease. Outdated harvest methods and over-fishing have destroyed or damaged reef structures. Unsustainable harvesting habits and a steady decline in water quality has led to greatly diminished oyster reef habitat on all our coasts.
Dredges and tong harvesting, which scrape living oysters off the reef, can destroy the reef height and structure. It may take decades for a reef harvested with these methods to recover, diminishing habitat for young fish and crabs. Continual dredging along in Atlantic Coast estuaries has resulted in significant loss of three-dimensional reef structures. Overfishing has reduced many oyster reefs to a thin layer close to the bottom. Oysters, however, grow faster and larger higher in the water column, atop reef structures.
Many factors adversely affect water quality and oyster reef health. Runoff and erosion from industry, farming, and development contribute to lower salinity, low oxygen levels, and silt overload. Waste, toxins, and excess nutrients end up in the water, weakening oysters and increasing the spread of disease. Over-sedimentation reduces available nutrition and pollutes the hard bottom habitat that these shellfish require. As oysters decline in health and numbers, their remarkable ability to filter water is diminished, resulting in poorer water quality. The cycle is difficult to reverse.
What We Do
We Protect Oyster Habitat
We do extensive research on the science and techniques behind oyster restoration to address decades of reef damage and loss. To bolster oyster populations and oyster reef habitat, we map oyster bed conditions, monitor water quality, and share our findings with industry and conservation partners. For example, the NOAA Chesapeake Bay Office provides Maryland and Virginia oyster restoration partners with GIS-ready acoustic mapping to identify current distribution, structure, and quality of oyster habitat.
Turning the tide on the oyster decline requires cooperative efforts from committed partners. We play an active role in convening workgroups, establishing goals, and measuring progress. We also offer grants for developing oyster aquaculture and habitat improvement. Our partners include:
Local and national waterway and oyster organizations.
State wildlife and environment officials.
Federal agencies, such as the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers.
We Restore Oyster Habitat
The NOAA Restoration Center has funded more than 70 oyster restoration projects in 15 states. Some of the restoration techniques include:
Quickly distributing large amounts of shell with high pressure hoses to provide a suitable base for oysters.
Constructing a linear reef of shell and rock to stabilize the shoreline and protect seagrass plantings behind the reef, enhancing shoreline stability and providing additional habitat for other reef inhabitants.
Collecting and bagging oyster shell for use as cultch (the mass of stones, shell, and grit that oyster beds are made of) for spat. Like a quick-start habitat, these bags of oyster shell will help establish new reefs in intertidal areas.
Creating hatcheries to provide seed oysters in areas where oyster reproduction is nonexistent or unreliable. This will establish new reefs and improve local water quality.
A Leading Role in the World's Largest Oyster Restoration Effort
NOAA Fisheries provides scientific support for oyster restoration around the country.In the Chesapeake Bay, oyster populations are only about 1% of historical levels due to disease, pollution, and overharvesting. To meet our goal to restore oysters in 10 Chesapeake Bay tributaries by 2025, NOAA is an active partner in the Chesapeake Bay Program, which focuses on large-scale oyster restoration projects.
As part of this effort, NOAA's Chesapeake Bay Office conducts sonar surveys and develops analyses of existing habitat. This information helps planners decide where to restore oyster reefs and track reef health after the restoration is completed.
We measure the success of tributary projects against high standards for the percentage of restorable bottom converted to healthy reef and for oyster density and reef biomass. To ensure there are enough oysters to produce a self-sustaining population, these projects are significantly larger than similar projects only a decade ago.
For example, since 2011, NOAA has worked with partners to plant more than 3 billion oysters on 563 acres of restored oyster reefs in the Choptank River complex on Maryland’s Eastern Shore. More impressively, 100% of the reefs that were planted with oyster spat in 2012 and 97% of those planted in 2013 are thriving (PDF, 70 pages).
The NOAA Chesapeake Bay Office is also conducting and funding research to quantify the benefits restored oyster reefs bring to both the ecosystem and our economy.
We Partner to Support Oyster Reef Habitat
NOAA’s community-based oyster restoration projects draw strength from partnerships with other federal agencies as well as local stakeholders. Local water-oriented organizations are especially important because they engage their members in volunteer efforts.
In the Pacific Northwest, we work with tribes, states, the shellfish industry, and local organizations to rebuild dense, breeding populations of Olympia Oysters in Puget Sound. NOAA maintains a native shellfish hatchery, providing seed stock for restoration efforts. The goal is to restore at least 100 acres of native oyster habitat in Puget Sound by 2020.
Nationwide, nearly 17,000 volunteers have participated in this and other NOAA oyster restoration projects.