Restoring California's Native Oyster

It’s the best oyster you’ve (probably) never tasted. For years, many people assumed it was gone from Tomales Bay altogether. But one day, Joe Newman, a Developmental Technician in the Aquatic Resources Group (ARG) at the University of California, Davis, Bodega Marine Laboratory (BML), got a call from a local oyster grower, who jokingly told him to “grab a bottle of hot sauce” and head to a nearby boat launch. Intrigued, Joe investigated and found that California's only native oyster species — Olympia oysters (Ostrea lurida), affectionately known as "Olys" — were indeed there. That discovery years ago wasn't just a welcome surprise. It was a reminder that although the species had declined, it hadn't disappeared from the bay.

Once plentiful along the coast, Olympia oysters were severely overharvested during the California Gold Rush and later impacted by silt from hydraulic mining and other changes to their coastal habitat. Today, they remain at roughly 1% of their historic abundance. But the loss isn’t just about the oysters themselves. As oyster beds disappeared, so did the habitat they created: places where young fish and other animals could shelter and feed while the oysters filtered water and helped stabilize shorelines. Now, decades of work, from pioneering hatchery techniques to ambitious restoration efforts, are helping bring that habitat back.

Hatchery History

Finding remnant Olympia oysters in Tomales Bay answered one important question: the species wasn’t gone. But with just a fraction of its historic population remaining, how could those numbers ever recover? That answer began taking shape in an unlikely place: beneath the flight paths of San Francisco International Airport. 

In the 1990s, Karl Menard, Animal Care Supervisor at BML and leader of the Aquatic Resources Group, and the ARG team were hired to conduct an underwater survey at the San Francisco airport as part of a proposed plan to expand the runways. During the survey, they discovered an unexpected resident: wild Olympia oysters growing under the airport on backfill and torn-up materials associated with the Loma Prieta earthquake. The oysters had managed to survive and grow in a highly altered, human-made environment — evidence that they could make use of habitat far removed from the natural oyster beds they once occupied. This sparked a new question: if Olympia oysters could thrive in an artificial setting like this, could researchers recreate the conditions they needed to grow in a hatchery?

Unlike most oysters, Olympia oysters don't simply release eggs and sperm into open water. Females brood developing larvae inside their shells before releasing them into the water, making them much trickier to culture in a hatchery. 

But biology wasn't the only hurdle. Successful cultivation also required experimentation and innovation. The ARG team designed and fabricated custom PVC settlement plates that gave larvae a place to grow in the hatchery and, eventually, a portable way to bring them into the field for research. Together, those advances made it possible to produce Olympia oysters for research and, eventually, restoration.

Science and Success

Successfully culturing Olympia oysters opened the door to new questions about what it would take for wild populations to recover. For Dr. Ted Grosholz, Distinguished Professor (now Emeritus) at UC Davis, Olympia oysters became an ideal species for exploring how environmental conditions shape survival and restoration success. Together with his graduate students, he investigated how ocean acidification, nutrient availability and changing estuarine conditions affected oyster survival.

Grosholz and his students moved bags of juvenile oysters from the hatchery into the bay, exposing them to seasonal upwelling, storms and baseline conditions. By monitoring the survival rate, they began to understand what conditions offered the best chance for successful restoration. But even as they learned what it takes for Olympia oysters to survive, one problem remained: “The population just couldn't get going,” explains Grosholz, “There just weren't enough small baby oysters coming into the system... We really needed to use hatchery production to try to jumpstart the number of oysters in the bay.” The idea of using hatchery production to give wild Olympia oyster populations a boost eventually moved from a research question to a real-world restoration project on the shoreline.

Back to the Bay

In June 2026, 125,000 oysters found a home at Sacramento Landing in Point Reyes, the first “wild site” outplanting of restored Olympia oysters and a culmination of decades of lab and field work. Early one morning, teams from UC Davis and The Nature Conservancy (TNC) donned warm jackets and soft gloves to settle the young oysters into their new home. Crate by crate, rock by rock, oyster by oyster, it was a strange sort of homecoming for a species that had nearly disappeared from these shores.

Making that homecoming possible required years of scientific research. It also depended on a partnership between UC Davis and TNC that brought expertise in oyster biology together with the funding and practical tools needed to restore native shellfish at meaningful scales. 

Unlike previous outplantings on the farms at Hog Island Oyster Co. and Bodega Bay Oyster Company, the oysters at Sacramento Landing won't be harvested. Instead, they'll be monitored as they grow, reproduce and begin rebuilding a wild population. Leaving the oysters in place permanently not only gives them a chance to grow and breed in situ, but it also means Sacramento Landing has regained a native, habitat-building species that will support a variety of life. As Newman describes, “Once (their population) gets going, they actually create habitat for lots and lots of other species... We've done work like this in other places, like San Francisco Bay, where there are tagged fishes, and we've found sturgeon, salmon and shorebirds among the oyster beds.”

Growing Beyond the Hatchery

For Dr. Phoebe Racine, an Estuarine Project Director at The Nature Conservancy in California, the success of Sacramento Landing isn't just measured by the 125,000 oysters placed in the water. It's measured by what those oysters do next.

In this case, hatcheries are used to create a foundation population, but when those oysters end up on farms along the coast or in restored sites like Sacramento Landing, they begin breeding. Almost imperceptibly, lab-grown oysters start to contribute larvae to the wild population. It’s a form of restoration that’s easy to overlook. But when there are enough farmed and restored oysters on the coast, this “background” breeding really starts to add up, increasing the chance that wild populations can reproduce at self-sustaining numbers in the future. This idea – that aquaculture can support restoration not only by producing oysters, but by helping rebuild wild populations over time – is at the heart of what's known as restoration aquaculture. 

Building for Scale

Restoration aquaculture represents a long-term vision for this and other species, but it will also require enough oysters to make it possible. That’s where techniques like remote setting come in. Until now, restoring a site far from a hatchery meant loading rocks and juvenile oysters onto trucks and transporting them back and forth between the laboratory and the shoreline. Remote setting offers another approach. Instead of bringing young oysters from the hatchery to the site, the site will become the hatchery. Tanks with flowing seawater will be placed literally just a few hundred yards from a restoration site, allowing larvae to settle and grow on rocks or settlement plates before being moved a short distance into the water. 

Although remote setting has been used successfully in other parts of the world, applying it to Olympia oyster restoration on the California coast represents a new approach. By reducing transportation and bringing cultivation closer to restoration sites, remote setting can potentially expand the number of oysters that can be grown at once. As Racine notes, it also creates new opportunities for undergraduate students to gain hands-on experience in aquaculture and restoration while working alongside experienced researchers.

Restoring Together

Scaling restoration doesn't just require new ideas; it also requires new ways for research and industry to work together. Recently, UC Davis worked in collaboration with the California Department of Fish and Wildlife to create commercial permitting pathways that allow university marine laboratories to combine restoration research with commercial seed production in the same facility. 

Now, researchers can continue studying native oysters while also supplying commercial growers with locally produced oyster seed from a variety of species. For growers, that means a larger portfolio of oysters to cultivate, including native Olympia oysters that are not susceptible to some of the diseases that affect commercial Pacific and Kumamoto oysters, such as OSHV-1. Having access to locally produced seed also reduces dependence on imported seed from outside California, potentially reducing the risk of introducing unwanted pathogens or non-native organisms. They can also grow native species on their farms, which will contribute to the “background restoration” effect by allowing native species to breed in the waters along the coast. In this way, commercial aquaculture and restoration become partners rather than separate pursuits, each expanding the other's impact.

A New Model for Restoration

What began with a handful of remnant oysters, a joking reference to a bottle of hot sauce and decades of patient research is becoming a new model for bringing native species back to California's coast. The goal isn't simply to produce more oysters. It's to restore enough of them that they can begin rebuilding their own populations, creating habitat, supporting coastal communities and carrying the work forward long after the last crate has been unloaded.