Olympia oysters, whose slender, two-inch shells can be found in historic Native American sites across the Bay Area, were believed to thrive in the shallow water below the tide. But more than a century after nearly disappearing, the Olys could make a comeback at Point Pinole.
The Gold Rush era and the rise of hydraulic mining sent waves of mud downriver, covering the hard bedrock off Richmond’s north shoreline, destroying much of the shellfish’s ideal habitat.
“Combine that with overharvesting and lower water quality and you can wipe them out, but there are still pockets of native oysters in the Bay,” said Christopher Lim, Living Shoreline project manager at the Watershed Project.
The Richmond-based environmental group will soon begin an effort to rebuild the Olys’ habitat using 100 artificial reefs. Larval oysters float through the Bay in search of a rough surface to attach to and grow – in this case, that surface will be the 250-pound dome structures.
“So when someone says oysters don’t move that’s not true,” Lim said. “They move when they’re very young.”
Relative to their Japanese Pacific oyster cousins often found at restaurants, Olympia oysters are smaller at about two inches long. Native Americans used them for meat and to build shellmounds found up and down the coast, creating an historic record of sorts that Olys were once abundant in the region.
Exact numbers, however, are hard to come by because early documenters may have confused native oysters with transplants from Washington and Oregon. Current subtidal populations are also difficult to estimate because the oyster beds are hard to see or reach in shallow water using most remote-sensing techniques, according to The San Francisco Bay Subtidal Goals Report, a guide to restoration and protection opportunities in the area.
In restoring oyster habitat, scientists hope to see an ecological chain reaction.
Oysters are considered a keystone species, meaning their presence has a profound impact on the surrounding ecosystem. As filter feeders, the mollusks – in a large enough population – can actually clean the surrounding water.
In rebuilding the oyster beds, scientists want to find out if clearer water will allow eelgrass to thrive, thus providing food for oysters, crabs, worms and other critters, and shelter for fish. The oysters also provide food for certain kinds of snails and crabs, which provide food for birds and fish – and if all goes well a new little ecosystem emerges around the man-made reefs.
Having the robust structures offshore could also serve as a protective barrier from waves that erode the coast, said Marilyn Latta, a project manager at the California Coastal Conservancy.
Scientists are still developing an understanding of the Olympia oyster, basing new experiments on early work done with Olys on the West Coast, and on more established approaches with other oyster species on the East Coast and internationally, Latta said. Lessons learned from these small-scale, experimental restorations in the Bay could eventually inform a more significant project.
The reefs, molded from a mix of old Olympia oyster shells, dredged Bay sand and concrete called baycrete, is a more environmentally friendly material in which to create marine habitat, Lim said. A mock reef at the Watershed Project office looks like a rough, gray dome, pocked with oyster shells. Holes throughout the reef’s surface allow oysters, fish and crabs to hide inside.
Once the reefs are built and the proper permits acquired, volunteers will deploy the baycrete domes at Point Pinole as early as next summer, Lim said.
The Watershed Project’s effort joins with the San Francisco Bay Native Oyster Working Group, an amalgamation of scientists, academics and government officials working together on restoration projects.
The Subtidal Goals Report pegs Point Pinole as a potential hotspot for oyster habitat restoration because of its ideal conditions for the shellfish and its existing and historic population.
If the Olys do return to Point Pinole, Lim advised against hunting in the Bay for a snack, even though he said he finds the native species taste better than the Pacific oyster. More research needs to be done to determine if oysters in the Bay are safe to eat, Lim said. In fish, toxins are stored in fat, but oysters don’t have fat.
“For now, I recommend not trying them,” he said.