Will Olympia oysters survive in the Bay?

We waded through murky bay waters and patches of deep mud under the light of the moon and our headlamps. Cool water sloshed over the tops of our boots and covered our toes. We moved slowly and carefully across the slick bottom of the bay. The tide was going out, nearing its lowest mark, and the oyster reef balls had begun to appear as the receding waters exposed them. 

Watershed project volunteers huddled around the reef balls with scrub brushes, quadrangles, clipboards and rulers in hand. They were looking this late evening in October for Olympia oysters, the species native to our coastline. 

Oysters were once “plentiful beyond modern conception” in the San Francisco Bay, in the words of author Malcolm Margolin in his book The Ohlone Way, but their populations declined substantially around the time of the California gold rush. The question the volunteers were trying to answer was whether a recent effort to repopulate the bay with oysters was having any success. 

“For a long time, people thought oysters were gone here, that there just were not any left,” said Helen Fitanides, program manager at the Watershed Project, a nonprofit based out of Richmond that is working to restore the oyster habitat in the bay. A combination of overfishing, pollution and habitat loss had all but wiped them out. Hydraulic mining brought large amounts of sand and sediment down from the Sierra Nevada mountains and into the bay, burying their rocky habitats. 

“Oysters need to live on something hard,” Fitanides said. “If they glue themselves to a tiny rock or piece of sand, they are just going to sink in the mud and die, especially out here. It’s mostly mud.”

The Watershed Project in 2013 deployed 100 artificial reef balls at Point Pinole as an experiment to see if this would help the oysters repopulate. The reef balls, which are made of crushed oyster shells, sand and concrete, provide a hard surface for the oysters to grow on, and the population grew exponentially within three years into 30,000 oysters; however, in 2017, an unusually high amount of precipitation over a prolonged period decreased salinity in the bay, killing 97% of the new oyster reef population. 

Watershed Project’s scientists and volunteers are continuing to monitor the oysters and are hoping to see the population recover. After carefully peeling off green sea lettuce and removing sediment from a portion of a reef ball, Anne Bremer, education and community outreach coordinator at the Watershed Project, leaned in to get a better look. Several baby oysters, called “oyster spat” were visible. 

“This fall is the first time that I’ve seen live oysters on these reef balls,” Bremer said. 

Oysters play a significant role in the health of the bay. As filter feeders, they help clear pollution from the water. As they grow on top of each other, they form reefs that can help protect the shoreline from climate change and associated sea level rise. 

Although much uncertainty remains about the long-term recovery of oyster populations in the bay, this fall the oyster population recovery took a positive turn. Everyone found at least one oyster on a plot. “I’m so excited about this. It has been a year and a half of looking and often not finding. There were some days when we didn’t find anything,” Fitanides said.