A NOAA Fisheries study has some bad news for southern resident killer whales. Their favorite prey—Chinook—are among the most vulnerable anadromous fish on the Pacific coast to climate change.
The new study assessed 33 Pacific salmon and steelhead runs—including 14 in the Columbia Basin—and ranked their vulnerability based on 20 attributes of the run, such as its time of migration, genetic diversity and thermal tolerance. Most of the runs are threatened or endangered under the Endangered Species Act.
Of the seven runs facing a very high risk of vulnerability from a warming climate, five of them are Chinook. That includes the Snake River spring/summer Chinook and the Upper Willamette River Chinook, along with two Chinook runs in California’s Central Valley and one in the Sacramento River.
One other Columbia Basin run—the endangered Snake River sockeye—also ranked very high in NOAA’s first comprehensive climate vulnerability assessment for West Coast salmon and steelhead.
“Steelhead, pink and chum salmon face less risk, either because they are more adaptable to varying conditions (steelhead) or spend less time in freshwater (pink and chum),” a news release from the agency said. The Columbia River runs with the best ability to adapt include lower Columbia Chinook, lower Columbia steelhead, and Snake River fall Chinook.
The peer-reviewed study was published July 24 in PLOS One, an open access journal of the Public Library of Science.
Scientists at NOAA’s Northwest Fisheries Science Center wanted to identify which populations may need the most help as some of the expected conditions of climate change materialize, such as warmer stream temperatures, low summer flows and a more acidic ocean.
“Our goal was to pull together the most relevant information we have about Pacific salmon and make it easily available for decision makers, researchers, the public, and anyone supporting recovery actions across the West Coast,” Lisa Crozier, NOAA research scientist and the study’s lead author told NW Fishletter.
She said policy decisions about the best actions for protecting salmon and steelhead must take many things into account, but noted that this analysis can give them a basis for understanding which species face significant risks, and why.
Scientists used three components to rate vulnerability—sensitivity rates how strong each run is liked to the present climate; exposure is the magnitude of projected change in local environmental conditions; and adaptive capacity is the ability of the run to cope with new conditions.
Of the 14 Columbia River fish assessed, three rank “very high” for risk, eight rank “high,” and three face a “moderate risk.”
Of those that have very high vulnerability overall, Snake River spring/summer Chinook ranked “very high” in exposure risks, while Snake River sockeye and Upper Willamette River Chinook ranked “very high” in sensitivity risks.
The mid-Columbia spring Chinook is borderline, and close to facing a “very high” risk due to exposure risks including its vulnerability to stream temperatures, ocean acidification and sea surface temperatures, Crozier said.
“The Chinook and sockeye also scored high in risk of regime shift, because the Interior Columbia has the largest amount of spawning habitat that is projected to change from snow dominant to transitional or rain dominant of any region,” she added.
Crozier said it’s not a coincidence that the runs that are listed as endangered—especially those with a very high climate sensitivity—are also the runs with the highest risk overall.
The article noted that to keep pace with climate change, genetic adaptation may be needed.
“Many traits appear to have responded to recent climate change, apparently without genetic adaptation,” the article said. “However, to keep pace with climate change, genetic adaptation may be necessary in the long-run; thus, maintaining genetic diversity within [distinct population segments] and species as a whole is a high priority for salmon conservation.”
Scientists expect some populations to shift their migration times to earlier or later in the season compared with historical runs to avoid mid-summer heat. “The fish will change; we have to be prepared for that,” Crozier said.
The assessment is an effort to help fish managers find ways to mitigate for the impacts and focus on species that may need the most help. Crozier said there are many restoration efforts that could benefit from the assessment. Efforts like the Yakima Basin Integrated Plan, which has developed plans to respond to potential water shortages in the entire basin.
“There really are solutions when people pull together,” she said. “I really feel like that’s the direction we need to go. Solutions that are good for salmon are also good in many other aspects. It can be presented as this water war, but it doesn’t have to be that way.”
The analysis was NOAA Fisheries’ second climate vulnerability assessment to be completed. In 2016, the agency conducted an assessment of northeast fisheries. It is also working on another climate vulnerability assessment of West Coast marine fish, Crozier said.
The method of assessment is designed for rapid assessment by using a variety of widely available data, according to the PLOS One article. “It assumes that vulnerability will be periodically re-assessed, and the method refined as status reviews are updated,” it said.