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.

More in News

Suspect arrested for Kirkland Key Bank robbery needed money for rent

Media outlets led police to man’s identification.

King County Correctional Facility is located at 500 5th Ave., Seattle. File photo
King County jail’s leaky pipes have national implications

Lawsuit filed in King County Superior Court alleges Aquatherm has been selling faulty pipes.

Siri Bliesner, Susan Wilkins and John Towers compete for Lake Washington School District Director District 5 position. Courtesy photos
Three candidates aim to fill an open seat on the Lake Washington School Board

Siri Bliesner, John Towers and Susan Wilkins compete for Lake Washington School District Director District 5 position.

Kirkland resident Elizabeth Standal holds broken heart at the Lights for Liberty Vigil on July 12. Stephanie Quiroz/staff photo
Lights for Liberty Vigil in Kirkland protests conditions of migrant camps

The Kol Ami congregation gathered July 12 for the Lights for Liberty Vigil, calling for an end “human concentration camps.”

VoteWA is a $9.5 million program that came online last May and is meant to unify all 39 county voting systems in the state into a single entity. Courtesy image
WA’s new voting system concerns county elections officials

VoteWA has run into some problems in recent months as the Aug. 6 primary election draws closer.

PSE’s battery storage project could help the clean energy roll-out

The tiny pilot project in Glacier could eventually be expanded.

Kirkland officer fatally shoots man threatening 18-month-old child

King County Sheriff’s Office will conduct investigation into shooting.

An aerial photo shows the locations of two earthquakes and five aftershocks in and near Monroe, which rattled the Puget Sound region early Friday. The first was the magnitude 4.6 quake at upper right, 13 miles under the intersection of U.S. 2 and Fryelands Boulevard SE at 2:51 a.m. The second, magnitude 3.5, occurred 18 miles under the Old Snohomish-Monroe Road at 2:53 a.m. The aftershocks followed during the ensuing two hours. This image depicts an area about 3 miles wide. (Herald staff and the Pacific Northwest Seismic Network)
Early wake-up call: Twin quakes under Monroe rattle region

Thousands of people felt them. They were magnitude 4.6 and 3.5 and hit minutes apart.

Most Read