Two-thirds of 64 California Current stocks vulnerable to climate change, NOAA finds

Recent research from NOAA found 67 percent of 64 federally managed species in the California Current large marine ecosystem, extending from the U.S.-Canadian border to the southern tip of the Baja California peninsula in Mexico, to be at least moderately vulnerable to climate change, with 23 percent considered highly or very highly vulnerable.

Scientists from NOAA and the U.S. Geological Survey, in partnership with the University of California, Davis, and University of California, Santa Cruz, published “Vulnerability to climate change of managed stocks in the California Current large marine ecosystem” on 21 February, 2023. Their paper predicted only one species will have a positive response to climate change in the entire marine environment.

“Overwhelmingly, our assessment indicates that the effects of climate change will be negative to neutral, with the exception of arrowtooth flounder,” Michelle McClure, the director of NOAA’s Pacific Marine Environmental Laboratory and the lead author of the study, said.

The paper focused on how changes in sea surface temperature, air temperature, sea surface salinity, precipitation, surface pH, subsurface oxygen, phenology, and the strength of upwelling favorable winds, currents, and sea level rise are affecting fish populations.

Species that are at the greatest risk, according to the study, include green sturgeon and chinook salmon, but many other species with a high market value also underwent evaluation including Pacific hake, salmon, and albacore tuna. Salmon, rockfish, and other anadromous fish are likely to experience the greatest negative impacts from climate change, the study found.

“One of the things about climate change is that we don't know how it’s going to play out [with] every factor,” McClure told SeafoodSource. “The challenge is, for most of our species, the actual impacts are several steps down through the food web and how that actually propagates through the food web is much more uncertain.”

Species received a rating from low to very high based on three categories: climate vulnerability, potential for distribution change, and directional effect, together indicating the likelihood climate change effects will be negative, neutral, or positive for each type of studied fish. There were 12 sensitivity attributes also studied for each species, including habitat specificity, prey specificity, adult mobility, spawning cycle, and more that experts, regarding specific species, quantitatively marked as having or not having “vulnerability.”

“[A] key element is that the level of risk is not uniformly distributed across species. Those species that have low population growth rate, those species that tend to be specialists in something, or that have a lot of other anthropogenic stressors – human-caused stressors – on them, tend to be the most vulnerable,” McClure said. “The good news about those with human-caused stressors is that we have other levers that we can pull other than climate.”

Characteristics such as habitat specialization, long lifespans, low population growth rates, and high commercial value, as well as impacts from non-climate stressors such as anthropogenic habitat degradation, are a commonality among highly or very highly vulnerable species, according to McClure.

The mobility of each fish species also impacts its vulnerability rating, according to the study. Highly mobile or migratory species can move habitats over a wide range, leading to a prediction of high distribution change but low vulnerability to climate change. Habitat specialists, conversely, tend to stay in one specific area and, thus, cannot escape unfavorable conditions, generating a higher vulnerability to climate change …

Photo courtesy of NOAA