California shellfish farmers adapt to climate change

Shellfish farmers at Hog Island Oyster Farm in Tomales Bay, Northern California. Credit: Remy Hale/Hog Island Oyster Co.

Due to their proximity to the ocean, Californians can enjoy locally sourced oysters, mussels, abalone and clams. Most of the shellfish eaten here comes from fish farms along the coast from San Diego to Humboldt County. And because the animals are filter feeders that siphon tiny plankton from seawater, their growth is ecologically sustainable.

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

“There have been calls across the state and in the United States to increase aquaculture production because it’s so sustainable. But at the same time, it’s a very vulnerable industry,” said Melissa Ward, a postdoctoral fellow at San Diego State University.

In a new study, researchers from SDSU and Oregon State University surveyed Californian shellfish farmers to find out how they perceive ocean acidification and what strategies they believe will help their operations adapt to environmental conditions. changing.

“This study is quite unique in that we’re getting insights directly from people who are impacted by the change and learning directly from their experiences,” said geographer Arielle Levine, director of the sustainability program at the College of Arts. and letters from SDSU.

Ward added that “they are on the front line observing climate change and will also be in the best position to describe what they think they need to adapt to these changes.”

Growing threat

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

As the water becomes more acidic, the calcium carbonate requirements of shellfish for their shells are less abundant.

“And so they’re basically running out of building blocks to build a hull with,” Ward said. “And that can be especially difficult for a very, very small shell that has just formed.”

Most shellfish are laid in land-based hatcheries. When they are about the size of a fingernail, they are moved to floating nurseries in the ocean.

“And at that point they’re kind of subject to all the conditions and the food floating around in the water,” Ward said.

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

Coping Strategies

Interviews with shellfish farmers revealed that although they are concerned about the impact of ocean acidification on their operations, they often lack the scientific instruments to know when it is happening.

Growers also worry about other environmental threats such as warmer water, heavy rains and pollution, all of which contribute to the spread of marine diseases, as well as toxic algae blooms.

“Sometimes producers would lose 90 to 100 percent of their shells in a given area, and they didn’t really know why,” Ward said. “It’s kind of a story of multiple stressors; you can imagine a time when the water is particularly hot or there is a rainy event, and eventually you can hit a tipping point that the seashells in the water just can’t resist.

Many producers said they needed access to scientific resources to identify the environmental factors involved in large mass mortality events and to potentially prevent them.

Policy change

All shellfish growers felt that the regulatory and permit requirements for shellfish farms needed to be adjusted to meet the rapidly changing environment. For example, it may be wise to diversify a shellfish farm by cultivating a new species better adapted to ocean acidification. But obtaining the permits required for this can be onerous.

“California is probably the hardest state to get a license for shellfish farming, which apparently contradicts the messages coming from above,” Ward said. While state leaders recognize that shellfish farming is sustainable and an opportunity for economic growth, it can take years and hundreds of thousands of dollars for a producer to obtain a license for a new species. “And they just can’t afford that time and that money,” she added.

“We need to maintain the environmental protections that we have in California, but if we really want the industry to be resilient to environmental change, we need to somehow allow flexibility in the management of operations.”

Another coping strategy identified by shellfish farmers was the need for more networking opportunities – not only with other producers, but also with managers, scientists and decision makers – to share information and best practices. adaptation to environmental changes.

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

“This work really links the environmental changes that are happening and will continue to happen, and how that affects not just the species in the ocean, but also the people who depend on those species,” Levine said.

Yessotoxins produced by phytoplankton have caused summer shellfish kill events in Washington

More information:

Melissa Ward et al, California Shellfish Farmers: Perceptions of Changing Ocean Conditions and Strategies for Adaptive Capacity, Oceans and Coastal Management (2022). DOI: 10.1016/j.ocecoaman.2022.106155

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California Shellfish Farmers Adapt to Climate Change (2022, May 23)
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