Climate change could kill salmon’s sense of smell

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 in order 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 was published on Dec. 18 in the journal Global Change Biology and involved researchers at the NOAA Fisheries lab in Mukilteo setting up three tanks of saltwater with different pH levels. One had levels on par with today’s current average, while the next was set at levels predicted 50 years from now and another with 100-year levels.

Juvenile salmon were placed in each of the tanks and exposed to the various pH levels for two weeks. After two weeks, the team ran a series of tests where the fish were placed 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 signalling system that was impacted by higher levels of CO2 is one which is 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 out 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.




In consideration of how we voice our opinions in the modern world, we’ve closed comments on our websites. We value the opinions of our readers and we encourage you to keep the conversation going.

Please feel free to share your story tips by emailing editor@bellevuereporter.com.

To share your opinion for publication, submit a letter through our website https://www.bellevuereporter.com/submit-letter/. Include your name, address and daytime phone number. (We’ll only publish your name and hometown.) We reserve the right to edit letters, but if you keep yours to 300 words or less, we won’t ask you to shorten it.

More in News

Aaron Kunkler/staff photoAlvin Sweet is a resident of Martin Court in Seattle’s Georgetown neighborhood. Martin Court is a former motel which was transformed into a supportive housing complex two decades ago. New funding from King County’s Health through Housing ordinance could expand this type of program across the county.
King County wants to buy motels for emergency, affordable housing

The concept has proven results in addressing homelessness.

From police footage of the Oct. 24 protest. Courtesy photo/Bellevue Police Dept. Twitter Account
Bellevue protest saw no injuries, no property damage as city issued civil emergency

The protest on the Eastside from Seattle organizers made some noise Saturday

Courtesy photo
State demanded more drop boxes, and now it must pay for them

A King County judge says a law requiring more ballot boxes was an illegal unfunded mandate.

King County 2020 unemployment numbers. Source: Washington State Employment Security Department
Boeing, coronavirus likely to impact King County economy

Unemployment remained high in September.

Hilary Franz (left) and Sue Kuehl Pederson
Wildfires, forest health are key issues in race to lead DNR

Republican Sue Kuehl Pederson is challenging incumbent Commissioner of Public Lands Hilary Franz.

Photo courtesy of Bellevue Police Department
July shooting now believed to be ‘murder for hire scheme’

The ex wife of the victim and two teenage boys were arrested in connection to the shooting

Screenshot from the state Employment Security Department’s website at esd.wa.gov.
State still sifting through thousands of unemployment claims

The recent Lost Wages Assistance program pumped an extra $625 million to Washington’s unemployed.

power grid electricity power lines blackouts PG&E (Shutterstock)
State extends moratorium on some electric, gas shutoffs

Investor-owned electric and natural gas utilities in WA can’t disconnect customers through April.

Washington Democratic Gov. Jay Inslee (left) and Republican challenger Loren Culp during Wednesday's debate. (TVW) 20201007
Inslee, Culp joust on COVID, climate, crime in feisty debate

In their only televised match-up, the two gubernatorial candidates differed on pretty much everything.

Gov. Jay Inslee during his Oct. 6 news conference. (Screenshot)
Gov. Inslee loosens rules for bars, libraries and movie theaters

New rules come as coronavirus cases are on the rise statewide.

Jay Inslee (left) and Loren Culp
Inslee, Culp will meet in only televised debate Wednesday

The two candidates will answer questions for an hour but they will not be on stage together.

Cecil Lacy Jr. (Family photo)
Court: New trial in case of man who told police ‘Can’t breathe’

Cecil Lacy Jr. of Tulalip died in 2015 while in police custody.