Can Scientists Save California's Only Native Oysters? New Technique Shows Promise

2 min
Research coordinator Kerstin Wasson (L) and research biologist Susanne Fork check on Elkhorn Slough's new generation of baby Olympia oysters, which were born and raised in a lab. (Erika Mahoney/KAZU)

Elkhorn Slough — an estuary on the eastern shore of Monterey Bay next to Moss Landing, about halfway between Monterey and Santa Cruz — has been home to Olympia oysters for the last 8,000 years or so.

Olympia oysters are the only native oyster species on the West Coast, and their population is suffering. They've already gone extinct in parts of California, including Big Lagoon, Bolinas Lagoon and Morro Bay.

In Elkhorn Slough, their population has been steadily declining since the 1920s. Back then, oystermen harvested them by the thousands.

Now, with the slough's oyster population at risk of disappearing, scientists are trying to save them using a novel technique.

Wearing camouflage waders, Elkhorn Slough Reserve research biologist Susanne Fork trudges through the soft mud of the slough's shore, counting the number of oysters living on rocks along the muddy bank. She holds a clicker in her hand.

“Instead of having to keep the number in your head, you can just click once each time you see or feel a living oyster,” says Fork.

She counts about 200 at one spot.

“It's really low. You can see many, many more that are gaping and open. So they're dead,” Fork says.

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Elkhorn Slough Reserve research coordinator Kerstin Wasson has been working to save the slough’s Olympia oysters for over a decade. She says there are several factors why the population is so small.

“It’s hard for any population, once it drops below a few thousand, to find mates and reproduce successfully,” Wasson says.

The oysters are also threatened by pollution and crabs, and can get buried in the mud and suffocate.

Back in 2012, Wasson and her team tried protecting baby oysters by deploying man-made habitats for them to settle on. But it only worked that year. It was the last time Wasson saw baby oysters in the slough.

Now, researchers at Moss Landing Marine Laboratories are trying something new. They’re attempting to restore the population through aquaculture.

Baby oysters grow on clamshells tied to wooden stakes. Researchers planted 20,000 new baby oysters at Elkhorn Slough.
Baby oysters grow on clamshells tied to wooden stakes. Researchers planted 20,000 new baby oysters at Elkhorn Slough. (Erika Mahoney/KAZU)

Essentially farming in water, aquaculture is often used to grow seafood, including oysters. But now — for the first time in California — it's being used to restore native oysters to a wild habitat.

Daniel Gossard, a graduate student at Moss Landing Marine Labs, spent the summer raising baby Olympia oysters.

“Many species that we normally wouldn't think play an important role in our environment actually do. Oysters, for example, they play an important role in cleaning up water and increasing water quality,” he says.

Oysters help keep the water clean by filtering it through their gills.

In June, researchers took 50 adult oysters from the slough and helped them reproduce in the lab.

“These oysters are smaller than what you would think of as the oyster that you eat. The oyster is rigid, it’s very bumpy. It's a little bit of a coppery-green color,” Gossard says.

Researcher Daniel Gossard holds an adult Olympia oyster in his hand. Researchers took 50 adults out of Elkhorn Slough and brought them to a lab to reproduce. The adult stock will stay at the lab to reproduce again in the future.
Researcher Daniel Gossard holds an adult Olympia oyster in his hand. Researchers took 50 adults out of Elkhorn Slough and brought them to a lab to reproduce. The adult stock will stay at the lab to reproduce again in the future. (Erika Mahoney/KAZU)

These adults created thousands of babies who got a pampered start to life.

Researchers fed them an ideal diet. They ate micro-algae that researchers grew in the lab. They also gave them habitats made out of clamshells to settle on.

Then, in late October, volunteers transferred the young oysters to Elkhorn Slough. Wasson has been monitoring them closely. The hope is that this new generation of native Olympia oysters survives and reproduces.

“I hope everyone out there has a chance to see an Olympia oyster one day because they’re a native species really special to our coast that people have been interacting with for thousands of years,” Wasson says.

If this project works, she says it could become a model for restoring Olympia oyster populations along the California Coast.

Some good news? Wasson and Fork checked on the oysters again in early December. Wasson says although the smaller ones are struggling to survive, the bigger baby oysters are doing very well, and that they had about a 90 percent survival rate so far.