Trying Something New, Scientists Use Aquaculture To Save Native Oysters

Nov 29, 2018

Elkhorn Slough’s native oyster population is at risk of disappearing. Olympia oysters have made the Slough their home for 8,000 years. Now, scientists are trying to save the species using aquaculture.

Wearing camouflage waders, Susanne Fork trudges through soft mud of the shore of Elkhorn Slough. A flock of birds feeds in the still water.

Fork is a Research Biologist for the Elkhorn Slough Reserve. She’s 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 this spot.

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

These are Olympia Oysters. They’re the only native oyster on the West Coast. The population is suffering up and down the coast. Olympia Oysters have already gone extinct in parts of California: Big Lagoon, Bolinas Lagoon and Morro Bay.

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

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, 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.

So, researchers are trying something new. They’re attempting to restore the population through aquaculture.

That took place at Moss Landing Marine Laboratories. The Lab’s Aquaculture Facility is located in its Aquaria Room, which is full of aquariums with starfish and other sea creatures.

Aquaculture is essentially farming in water. It’s often used to grow seafood, including oysters.  In this case, scientists are using it to save a struggling species. This project marks the first time in California that aquaculture is being used to restore native oysters.

Daniel Gossard is a graduate student at Moss Landing Marine Labs. He 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,” says Gossard.

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

In June, Researchers took 50 adults 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 while holding an adult oyster in his hand.

These adults created thousands of babies who got a pampered start to life. Researchers fed them an ideal diet. They ate microalgae 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.  Research Coordinator Kerstin Wasson has been monitoring them closely.  

“I’m peeking at some right now and they look great, but we’ll get a thorough count in December,” Wasson says.

You have to look closely to see the oysters. The biggest ones are just the size of a dime, most are the size of a speck. But there are plenty, nearly 20,000 at this spot. 

The hope is that this new generation of native Olympia oysters survives and reproduces in Elkhorn Slough.

“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.

UPDATE 12/18/18:

Kerstin Wasson and Susanne 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 fantastic. She says they had about a 90% survival rate and are now the size of quarters.