Dungeness crab, Pacific herring, and red abalone are among the marine species most vulnerable to the changing climate's effect on California's coastal waters, a new study led by UC Santa Cruz researchers finds. In a paper published on February 12 in the journal PLOS Climate, the team seeks to help the California Department of Fish and Wildlife (CDFW) in its efforts to develop and implement climate-ready fisheries management strategies that adapt to challenges such as rising ocean temperatures, acidification, and deoxygenation.
The study, " A Collaborative Climate Vulnerability Assessment of California Marine Fishery Species ," was led by Timothy Frawley, an assistant project scientist at UC Santa Cruz's Institute of Marine Sciences, and Mikaela Provost, an assistant professor in UC Davis's Department of Wildlife, Fish, and Conservation Biology. The study was done in close collaboration with CDFW, fisheries scientists with the National Oceanic and Atmospheric Administration (NOAA), and individuals from the Nature Conservancy and California Ocean Protection Council.
"The results are striking," said Frawley, who's based in Monterey with the ecosystem-science division of NOAA's Southwest Fisheries Science Center. "Some of California's most economically and culturally important fisheries are assessed as being among the most vulnerable to projected future environmental changes."
Prior to earning his Ph.D. in marine biology, Frawley spent five years as a commercial fisherman in California, Alaska, and Maine. So the potential threat is palpable for him, and he knows all too well how serious the impact of dispersed or greatly diminished fisheries would have on local economies and communities.
Annually, regional fishing fleets land over 8,200 tons of Dungeness crab, contributing an average over $45 million dollars to local and regional coffers each year. While this crab fishery remains one of California's top commercial harvests, other fisheries ranked as highly vulnerable have already experienced significant declines. The recreational fishery for red abalone, which at one time was estimated to provide $24 to $44 million in annual value, has been closed since 2018; while the biomass supporting the San Francisco Bay Pacific herring fishery—which once attracted more than 400 boats—has declined by more than 75% as commercial operations have largely ceased.
"While overall across the Northeast Pacific, a species like Pacific Herring may do OK, try telling that to a herring fisherman based out of San Francisco Bay. If their resource moves hundreds of miles away, it's a big deal to them," Frawley said. "It's important to do these assessments at a scale that provides results that will be practical at the local level. So in that respect, this represents a step forward."
Species sensitivity to climate changes
In their study, the researchers evaluated the sensitivity and exposure of 34 fish and invertebrate species to projected changes in ocean conditions in California waters over two time periods to assess climate vulnerabilities: in the near future (2030-2060) and further out (2070-2100). By identifying relative vulnerabilities across this set of diverse species, the team sought to provide a foundation for integrating climate change into CDFW management and research priorities.
The study assessed vulnerability based on two key components:
Sensitivity based on species-specific biological traits like reproductive rate, habitat range, and susceptibility to ocean acidification.
Exposure to projected oceanographic changes, including sea surface temperature, salinity, acidification, upwelling, subsurface oxygen levels, and sea-level rise.
Vulnerability varied by species. Similar to the scenario regarding Pacific herring, market squid may shift north to colder waters off Oregon or Washington state, threatening significant disruption to local California fisheries. Other species, like Pacific bonito, may actually benefit from warming waters, expanding their range into the California Current.
Identifying the Most Vulnerable Species
The study categorizes species into four vulnerability levels: blue (least vulnerable), yellow, orange, and red (most vulnerable). Because red abalone are benthic (i.e., bottom-dwelling) species with limited mobility and are acutely susceptible to extreme events like marine heatwaves, these prized mollusks are classified as highly vulnerable. Over the longer time horizons—as the impacts of ocean acidification, sea level rise, and other stressors are expected to intensify—additional species such as Pacific herring, Dungeness crab, Pismo clam, and pink shrimp also fall into the red category.
Other species of concern include market squid and the California spiny lobster which, respectively, generate about $43.9 million and $10.7 million annually for the state's economy. The classification system provides a clear, intuitive framework for fisheries managers, enabling them to prioritize conservation and adaptation efforts.
"My experience working as a fisherman has inspired me to focus my work as a marine scientist on supporting coastal communities by providing them with information required to better navigate risk and uncertainty," Frawley said. "My time at sea impressed upon me the links and feedbacks between environmental variability and change and marine-resource-dependent industries and communities, as well as an appreciation for fisheries as a team sport."
Fishermen are often thought of as fiercely independent individuals. But Frawley said that's not entirely true. "To make the gears turn, it requires a team of individuals working together on deck, groups of boats sharing information; dock workers and truck drivers to unload and transport the product; buyers and processors to package and market it; and managers and scientists to set the harvest levels and ensure that operations are sustainable," he said.
The research team also included Stephanie Brodie and Mercedes Pozo Buil from UC Santa Cruz. They were joined by Lyall Bellquist, from the Nature Conservancy and Scripps Institution of Oceanography; Noah Ben-Aderet from the California Ocean Protection Council; Michael Jacox, Steven Bograd, and Elliott Hazen, all from NOAA's Southwest Fisheries Science Center; Huff McGonigal from Fathom Consulting, and CDFW's Kirsten Ramey.
This work was funded by a grant from the Resource Legacy Fund.
