California shellfish farmers adapt to climate change

San Diego State University and Oregon State University researchers probe growers’ strategies for keeping the sustainable industry resilient as oceans turn more acidic

Shellfish growers at Hog Island Oyster Farm in Tomales Bay, Northern California. Courtesy of Remy Hale/Hog Island Oyster Co.

Because of their proximity to the ocean, Californians get to enjoy locally-sourced oysters, mussels, abalone and clams. Most of the shellfish consumed here come from aquaculture farms along the coast — from San Diego to Humboldt County. And because the animals are filter feeders that siphon tiny plankton out of seawater, growing them is environmentally sustainable. 

But due to rising greenhouse gas emissions, the ocean has become more acidic, conditions hostile to shellfish growth.

In a new study, SDSU and Oregon State University researchers interviewed California shellfish growers to find out how they perceive ocean acidification, and to learn what strategies they think will help their operations adapt to changing environmental conditions. 

“This study is fairly unique in that we’re getting information directly from the people who are being affected by change and learning directly from their experiences,” said geographer Arielle Levine, director of the sustainability program in SDSU’s College of Arts and Letters.. 

Ward added: “They’re on the front lines of observing climate change and they also are going to be most well-suited to describe what they think they need to adapt to those changes.”

Growing threat

Burning coal, oil and natural gas emits carbon dioxide and other greenhouse gases into the atmosphere. About a third of that CO2 is absorbed by the ocean, reducing pH levels. 

As the water becomes more acidic, the calcium carbonate shellfish need for their shells is less abundant.

If the water is acidic, the baby shellfish may grow more slowly, or even die, making it harder for aquaculture farms to remain viable. 

Strategies for adaptation

Interviews with shellfish growers revealed that while they are concerned about the impact of ocean acidification on their operations, they often lack the scientific instrumentation to know when it’s happening.

Policy change

All of the shellfish growers felt that regulatory and permitting requirements for shellfish operations need to be adjusted to respond to the rapidly changing environment. For example, it might be wise to diversify a shellfish operation by growing a new species that is better adapted to ocean acidification. But obtaining the required permits for that can be onerous.

The study is published in the journal Ocean & Coastal Management. The researchers hope it will serve as a roadmap for improving the resilience of the aquaculture industry in California. 

San Diego State University (via EurekAlert!), 23 May 2022. Press release.

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