The Alluring World of Olympia Oysters, Native Building Blocks of California’s Estuaries

Why More Olys?

Supporting Olympia oyster populations in the San Francisco Bay is, at heart, about the greater health of the Bay. Cleaner, clearer waters in the Bay will support Olys, and rebuilding the Olympia oyster habitat will support a healthier, more productive Bay.

It is confirmed in paper after paper, survey after survey, and generally among ecologists around the world that oysters are hugely beneficial to the water and organisms around them. Olympia oyster beds create habitat, especially for small invertebrates, and promote larval settlement and general biodiversity, creating a feeding ground for ducks, crabs, fish, and so much more. These oyster beds are an iconic native estuarine environment that has been missing for way too long. The pilot projects restoring Olympia oysters in the San Francisco Bay—which have involved a remarkable partnership of Bay stewards—make clear it is worth the effort to rebuild this Oly world.

Though Olys process less water than their larger cousins, they filter the phytoplankton and other particles in the water directly around them, a bonus for nearby eelgrass and other primary producers that need light to grow. New experimental evidence makes clear that when Olympia oysters are in proximity to eelgrass the ecological functions are greater than when Olys or eelgrass are alone. The surrounding mud itself is more productive, and stores more carbon, and more fish are around. The resilience of these mixed shoreline communities—its diversity and its defense against rising sea level—increases.

Diagram showing likes and dislikes of Olys

+ Click to enlarge

Oly Preferences: Conditions that are beneficial to Oly longevity and conditions that are not.

Where is it Worth the Effort?

Olympia oysters have specific likes and dislikes. They need substrate to settle on that won’t get covered by shifting sediments, they need plenty of phytoplankton to eat, and they need consistently salty water. They will die off in a prolonged freshwater event. Salinity in the Bay can be inconsistent in the northern sections where a rainy or snowy season will bring vast quantities of fresh water down the rivers through the Delta into San Pablo Bay. Salinity is more consistent in the mid and southern sections of the Bay especially below San Mateo on the western side, however the east shore near Hayward is where the invasive, predatory oyster drills are most numerous. If the Atlantic oyster drill is prevalent in a given cove, they will attack any Olys they can reach. And then it is important to know how the larvae of oysters can travel around the Bay and where the currents and tides might leave them for settlement. It is a complicated brew of factors. Sometimes, it is most important to make the effort where it is convenient for people to access, relying on the Oly’s resilience and opportunism to grow in a variety of kinds of places.

SF Bay Living Shorelines Project at San Rafael. Bags of Pacific oyster shells are set out in blocks to create a dimensional reef for native oysters and other organisms to settle upon.

Photo from SCC

Local Conditions Need Local Solutions

Restoration techniques vary greatly depending on where they are happening and what purpose has been decided they can serve: habitat restoration or improving shoreline resilience. In the Bay where sediment quickly covers the bottom, Olys need hard substrate that sits off the bottom. In Elkhorn Slough, where natural larval recruitment is sluggish, experiments are progressing with cultured oyster spat for spreading on the historic Oly mudflats there to mature into adult oysters. Another type of restoration technique involves distributing recycled oyster and clam shells along the ocean bottom or on a mudflat to help recreate an actual oyster bed as they might have been historically. The calcium carbonate of the shells cues larvae to settle (this is how natural beds and reefs accumulate). Placing shell (known as cultch), either loosely or gathered in mesh bags, is perhaps the most common way restoration groups up and down the Pacific Coast support native oyster population resilience. In San Francisco Bay, however, the fine silt and clay bury loose shells quickly.

Six Bay Area Restoration Projects

The six Bay Area restoration sites highlighted here illustrate an array of experimental restoration techniques. Each is a pilot project aimed at learning which techniques might be best in specific conditions and at larger scales. Each project is linked to a dedicated page on the comprehensive Native Olympia Oyster Collaborative (NOOC) storymap where details and survey data can be found and reports downloaded. There are a total of 48 restoration projects in the NOOC gallery ranging from San Diego, California to the Salish Sea near the Canadian Border. We encourage you to dig into the details. There is something to learn from each project.

Click map dots for description and link to NOOC storymap

Oly spat settled on a large clam shell.

Photo from NOOC

“Living Shorelines” and Restoration Aquaculture

Agencies wanting to take a holistic approach to supporting shoreline communities have created the Living Shoreline designation for any approach that strategically places habitat treatments to achieve both physical shoreline protection and habitat restoration goals. This might involve placing both eelgrass and reefballs (to attract oysters and other species) in a given site. Since 2012, these sites have shown strong data supporting the substantial benefits of biodiversity, wave subsidence, and carbon capture at the sites that take this more comprehensive approach.

Restoration aquaculture refers to multiple techniques used to enhance the natural recruitment of oysters including the distribution of lab-raised larvae and spat at a particular site. Putting more babies in the system seems advantageous, especially in places where larval distribution is poor, such as Tomales Bay and Elkhorn Slough. This technique is being researched for use in San Francisco Bay. Commercial shellfish farmers are good at cultivating oysters from spawn to spat to settled bivalve, and productive partnerships develop when goals align. Oyster farmers have been growing Oly spat at their farms and helping restoration efforts up and down
the coast.

What Does Success Look Like in San Francisco Bay?

More native oysters is a great thing, but success also looks like collaboration between restoration agencies and communities to support a healthy bay, thriving with a diversity of wildlife. Whether Olympia oyster bed habitat restoration or a Living Shoreline design with multiple species and goals, each project takes tremendous coordination, goodwill, passion, and a singular mission to put resilience back into nearshore ecologies around the San Francisco Bay.

An Oly bed can accumulate into a true multilayered, multi-generational bed with different-sized Olys growing on top of themselves with plenty of barnacles and seaweed growing around them, crabs hiding in the crevices, and birds feasting at the low tide. This is true habitat generation and looks like success. A big rain year will turn this location back into a mudflat. Is it still a success? A close look at the rip-rapped shoreline of a city park or a row of reefballs reveals lots of individual Olys plastered to the rocks. They are not accumulated into beds. Is that success? Because goals and sites vary, different metrics for success are appropriate for different sites.

Oly populations will always surprise us with their resilience and opportunism. We need to be open to seeing them rebound in different ways and understand that their presence harkens to so much more beyond their calcium carbonate selves. The goal to rebuild the iconic estuarine oyster bed habitat is in turn the goal for continued collaboration by people of all types, all expertise, and all backgrounds towards clean water and a flourishing Bay.

Photo by SFEI / S. Bezalel

Betsy Peabody

Photo by Benjamin Drummond

As far back as the 1940s and 50s, Olympia oysters were found around Puget Sound on the nets and equipment of Pacific oyster growers, and the ecological benefits of Olys were studied and found to be plentiful. The Olympia oyster came to be understood as a foundation species—an organism on which many other species depend. The small crevices of an Oly bed are better suited to tiny forage fish, invertebrates, and seaweeds than the larger Pacific oysters; they are perfect forage food for white-winged scoters and other ducks. The cultural, culinary, and environmental role of oysters and oyster farming in Puget Sound has never been interrupted and is still a strong force for Tribes and others. Recovery of the Olympia oyster for its historic role in the Puget Sound ecology and culture, has had a wide range of dedicated stakeholders.

“Olys are always making us rethink our assumptions about what is possible…”

—Betsy Peabody, founder Puget Sound Restoration Fund

In 1999, the community-based effort took off when Puget Sound Restoration Fund (PSRF) collaborated with the Suquamish, Skokomish and Squaxin Island Tribes, Taylor Shellfish, and Washington Department of Fish & Wildlife to produce and spread Olys back onto beaches and mudflats they originally thrived on. These early forays have developed into a groundswell of Sound-wide Oly restoration efforts that have yielded millions of Olys in bays and inlets known for historic abundance; thousands of tons of Pacific oyster shell have been sprayed off of barges to create substrate (cultch) for wild oysters to grow on.

Restoration Across the Bioregion

The Native Olympia Oyster Collaborative is the active group of researchers and Olympia oyster experts who have been convening since 2008, and are committed to this native oyster across its entire range from Baja California to British Columbia. NOOC is a community of practice, with a shared vision of a network of thriving oysters all along the coast. Together they have focused on four approaches: outreach, conservation/restoration, science, and aquaculture to achieve their vision. They are a remarkable consortium of creative scientists, restoration practitioners, Tribal members, and shellfish growers involved in Olympia oyster research, restoration, and education.

NOOC website
NOOC Restoration Storymap