Climate Change Could Kill Salmon’s Sense of Smell

A report released by UW last month highlights further dangers higher CO2 levels pose to Coho salmon.

Coho salmon may lose their ability to smell and respond to danger as carbon-dioxide levels in saltwater continue to rise, making them easier prey for predators and making it harder for the salmon to navigate.

A study released by the University of Washington and the National Oceanic and Atmospheric Administration (NOAA) last month shows that higher levels of CO2, the primary pollutant driving climate change, could harm juvenile Coho salmon as more CO2 is absorbed by the ocean. Salmon use smell to detect predators and food, but also to return to the streams where they were born to both spawn and die.

Higher levels of CO2 can change the water’s chemistry, leading to more acidity. Previous studies have shown that pollution can interfere with a salmon’s sense of smell, causing what a UW summary called a “one-two punch” for the fish. The study, published on Dec. 18 in the journal Global Change Biology, involved researchers at the NOAA Fisheries lab in Mukilteo setting up three tanks of saltwater with different pH levels—one par with today’s current average, the second at levels predicted 50 years from now, and the third at 100-year levels.

Juvenile salmon were placed in each tank and exposed to the various pH levels for two weeks. After two weeks, the team ran a series of tests, placing the fish in a holding tank in which the smell of salmon skin extract was injected. This smell usually signals a predator has attacked another fish, therefore making them flee or hide. Fish in the current pH levels tank responded normally, but fish from the tanks with higher CO2 levels did not.

After this test, neural activity in each fish’s nose and brain, specifically in the olfactory bulb where smell is processed, were measured. All the fish could smell the odors, but the ones exposed to higher pH levels had their information processing altered. “At the nose level, we think the neurons are still detecting odors, but when the signals are processed in the brain, that’s where the messages are potentially getting altered,” said UW researcher Chase Williams in the summary.

Williams told the Weekly that the neural signaling system that was impacted by higher levels of CO2 is one widely shared across animals, including other species of fish and mammals. Williams wasn’t sure how this would impact the fish while they remained in freshwater, but once they venture into the ocean, it could be dangerous for the fish. “Having an impaired sense of smell in the wild is potentially a very dangerous thing,” he said.

Fish in the wild could become more indifferent to scents indicating predators and take longer to react to the smell. The summary also noted that navigation, reproduction, and hunting would also be impacted. Researchers will next look at whether increased CO2 levels can affect other fish species in similar ways, and Williams said new research will likely be published within the next two years. If it does, it could further harm Puget Sound salmon, which have seen their numbers dwindle in recent decades due to pollution, climate change, and overfishing.




Talk to us

Please share your story tips by emailing editor@seattleweekly.com.

More in News & Comment

Gov. Jay Inslee issued new guidance allowing the resumption of self-service buffets, salad bars, salsa bars, drink stations and other types of communal food sources in Phase 2. File photo
Buffets and salad bars back on the menu in King County

Gov. Jay Inslee has revised rules to allow self-serve food areas in Phase 2 of the state’s reopening.

Puget Sound renters will need housing assistance

Nonprofits, activists are expecting greater need as workers are laid off.

Brian Tilley (left) and Katie Dearman work the wash station Friday at Kate’s Greek American Deli in Everett. (Kevin Clark / The Herald)
Governor’s no-mask, no-service order begins across Washington

“Just do not ring up the sale,” Gov. Jay Inslee said about customers who do not don the proper masks.

King County homeless count: 11,751 people, up 5 percent from 2019

One night a year, volunteers spread out across Seattle and King County… Continue reading

Nurse Sylvia Keller, pictured with Gov. Jay Inslee, is on the front lines of the COVID-19 battle in Yakima County. Courtesy photo
Governor doubles down on mask rules

Inslee: Starting July 7, businesses do not serve those who do not wear a mask

State Capitol Building in Olympia. File photo
Politicians get pay raises, state workers get furloughs

A citizens panel approved the hikes in 2019. Unable to rescind them, lawmakers look to donate their extra earnings.

Human remains in West Seattle identified

Bags of body parts were found in a suitcase along a West Seattle beach on June 19.

Summer vehicle travel projected to decrease this year

Traffic this summer will likely be lighter across Washington state than previous… Continue reading

Governor Jay Inslee smiles and laughs Sept. 3, 2019, during a speech at the Lynnwood Link Extension groundbreaking in Lynnwood. A Thurston County judge ruled he exceeded his authority when he vetoed single sentences in the state transportation budget in 2019. (Olivia Vanni / Herald file)
Judge invalidates Gov. Inslee’s veto in roads budget

Lawmakers said the governor crossed a constitutional line.

Most Read