For decades, Coho salmon were turning up dead in urban streams the Pacific Northwest. The salmon would stop swimming straight, and then die before they had a chance to spawn. Researchers worried that unless they figured out the cause, the species would eventually go extinct. Enter a formidable crew of biologists, modelers, community scientists, environmental chemists. After eventually ruling out the obvious suspects — things like temperature, oxygen levels and known toxins — researchers eventually zeroed in on a prime suspect: chemicals in tires. But the question remained: Which one? If you liked this episode, check out our other episodes on satellites monitoring emissions and how air pollution could create superbugs.Want to hear more environmental stories or science mysteries? Tell us by emailing [email protected]!Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
Full Episode
You're listening to Shortwave from NPR. Hey, Shortwavers. Camila Dominovsky here in the host chair with a mystery. A decades-long puzzle centering on a string of inexplicable deaths. The victims were coho salmon showing up dead in urban streams in Puget Sound around Seattle today. in very suspicious circumstances.
That's Zhenyu Tian, whom you might call one of the lead detectives on this case. He was a postdoc research scientist at the Center for Urban Waters at the University of Washington-Tacoma
when he was called in to the case. These fish spawn in freshwater, strike off for the open seas, trek back to the place of their birth, but then they die before they can spawn. And this keeps happening for years.
If this trend continues, they might be extinct in a few decades. So that's the problem we want to solve.
And we was a lot of people. Biologists, modelers, community scientists, environmental chemists. Some researchers rule out all the obvious culprits. Temperature, oxygen, known toxins. It's none of those. They need a lead.
So I think the first big step is our collaborators, NOAA and the Washington State University.
They look through the data about where fish were dying and started running models.
They are getting this important clue that the mortality risk of coca salmon is related to traffic.
Traffic. It's something to do with the roads, the urban runoff. So after years of work, the list of suspects is narrowing, but what part of the runoff? Enter another team of scientists from the University of Washington, including Zhen Yu. They're testing chemicals in runoff.
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