California Shellfish Farmers Adapt to Climate Change

Newswise — Due to its proximity to the ocean, Californians can enjoy locally sourced oysters, mussels, abalone, and scallops. Most of the shellfish consumed here comes from aquaculture farms along the coast — from San Diego to Humboldt County. And because these animals are filter feeders sucking tiny plankton out of seawater, cultivating them is eco-friendly.

But due to increased greenhouse gas emissions, the oceans are becoming more acidic, conditions that do not support the growth of shellfish.

“There are calls across the state and across the US to increase aquaculture yields because it is so sustainable. But then 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, SDSU and Oregon State University researchers interviewed Californian shellfish farmers to find out how they view ocean acidification, and to learn what strategies they think will help their operations adapt to changing environmental conditions.

“This study is quite unique in that we get first-hand information from people affected by change and learn firsthand from their experiences,” said geographer Arielle Levine, director of sustainability programs at SDSU’s College of Arts and Letters.

Ward added: “They are at the forefront of observing climate change and they will also be best suited to describe what they think they need to adapt to that change.”

Growing threat

Burning coal, oil and natural gas releases carbon dioxide and other greenhouse gases into the atmosphere. About a third of CO. that2 absorbed by the ocean, reducing the pH level.

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

“So they basically ran out of materials to build the shells on,” Ward said. “And it can be very challenging for very small shells that are just forming.”

Most clams are spawned in land-based hatcheries. When they are the size of a fingernail, they are transferred to a floating nursery in the ocean.

“And at that point, they’re just subject to whatever conditions and whatever food floats in the water,” Ward said.

If the water is acidic, baby clams can grow more slowly, or even die, making it difficult for aquaculture farms to survive.

Strategy for adaptation

Interviews with shellfish farmers reveal that while they are concerned about the impact of ocean acidification on their operations, they often lack the scientific instrumentation to know when it occurs.

Farmers are also concerned about other environmental threats such as warmer water, heavy rains and pollution — all of which contribute to the spread of marine disease — as well as toxic algae blooms.

“Sometimes, farmers will lose 90, 100% of their shellfish in a certain area, and they don’t know why,” Ward said. “It’s kind of a story about the many causes of stress; You can imagine when the water is very warm or there is an event of rain, and eventually you might reach a tipping point where the shells in the water can’t survive.”

Many farmers say they need access to scientific resources to pinpoint the environmental factors involved in major mortality events, and potentially prevent them.

Policy changes

All shellfish growers feel that the regulatory and licensing requirements for shellfish operations need to be adapted to respond to the rapidly changing environment. For example, it may be wise to diversify shellfish operations by growing new species that are better adapted to ocean acidification. But getting the necessary permissions for it can be tough.

“California is probably the hardest state to get a mussel farming permit in, which seems to contradict the message coming from above,” said Ward. While state leaders recognize that clam farming is sustainable and represents an opportunity for economic growth, it can take years and hundreds of thousands of dollars for a grower to obtain permits for a new species. “And they can’t afford the time and money,” he added.

“We need to maintain the environmental protections we have in California, but if we really want this industry to be resilient to environmental change, we have to provide flexibility in farm management.”

Another adaptive strategy identified by mussel farmers is the need for more networking opportunities — not only with other farmers, but also with managers, scientists and policy makers — to share information and best practices to adapt to a changing environment.

The study was published in the journal Marine & Coastal Management. The researchers hope this will serve as a roadmap for increasing the resilience of the aquaculture industry in California.

“This work really draws the connection between environmental changes that are and will continue to occur, and how they are affecting not only the species in the oceans, but also the people who depend on these species,” Levine said.


About San Diego State University

San Diego State University is a premier public research institution providing transformative experiences for its more than 36,000 students. SDSU offers bachelor’s degrees in 96 fields, master’s degrees in 84 fields and doctorates in 23 fields, with additional certificates and programs at regional micro sites. SDSU is ranked as the number 1 California State University in federal research support, as one of the best public research universities in California. In addition to the academic offerings at SDSU, SDSU Imperial Valley and SDSU Georgia, SDSU Global Campus offers online training, certificates, and degrees in fields of study designed to meet the needs of students everywhere. Students participate in transformational research, international experiences, sustainability and entrepreneurial initiatives, internships and mentoring, and various student life and leadership opportunities. SDSU is committed to inclusive excellence and is known for its efforts to advance diversity and inclusion. SDSU is nationally recognized for its study abroad initiatives, veterans programs and LGBTQA+ student support, and its strong Division I Athletic Program. About 50% of SDSU’s undergraduate and graduate students are students of color. The university is on the grounds of Kumeyaay and was recently recognized as an Asia Pacific Native American Service Institute (AANAPISI). SDSU is also a long-established Hispanic Service Institute (HSI). The university’s rich campus life and location offer students opportunities to lead and engage with the creative and performing arts, career and internship opportunities with more than 491,000 living SDSU alumni, and vibrant cultural life in the greater San Diego and US-Mexico regions. big.


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