Highway 7 runs north-south through western Washington, carving its way through a landscape sparsely dotted with residences, farms, and a general store. The flush of late winter rain characteristic of the Pacific Northwest gives way to a green April, complete with blossoming trees and chirping birds. Ohop Creek, which runs under the highway, is part of the regional spawning grounds for coho salmon—juvenile fish spend the first phase of their lives here, before beginning their journey to the sea.

This land is the ancestral home to the Nisqually Tribe, which currently has more than 650 enrolled members. The 5,000-acre reservation is nearby, and the Tribe’s Department of Natural Resources does restoration work along Ohop Creek. The Nisqually people have a deep cultural tie to salmon—it is not only a mainstay of their traditional diet, but intrinsically linked to their identity as a fishing people. The Tribe has been actively involved in salmon recovery efforts for decades, and since late 2020, they’ve been specifically working to protect coho, which are being killed by a chemical we spread simply by having cars.

Just over a year ago, scientists in Washington identified 6PPD-quinone, which is used to weatherize car tires, as a chemical that is acutely toxic to coho salmon. Every car that drives along the two-lane Highway 7, or even parks in the area, contributes to the problem. In the small valley where the road crosses Ohop Creek, the Nisqually Tribe and their partners, including Seattle-based nonprofit Long Live the Kings, have installed a biofiltration system that they hope will intercept the chemical, and keep the fish alive.

In the fall or early winter, coho salmon leave the open ocean and begin a long swim up freshwater streams to spawn. They deposit their eggs, completing the cycle that will yield another generation of the silver fish that have been a cornerstone of the Pacific Northwest diet for generations. In 2019 alone, there were 27 million pounds of coho harvested for consumption in the U.S.

As they swim upstream, adult coho often come into contact with urbanized watersheds in cities like Seattle and Tacoma. Over the past two decades, scientists and residents have noticed something disturbing. Pre-spawn coho in these urban areas seem to suddenly take sick, become disoriented or dizzy, and die within hours.

“Very visible, almost like spiraling, almost like drunk,” said Zhenyu Tian, one of the researchers who identified 6PPD-quinone as a problem. “Gasping for air.”

Read the full article about coho salmon by Lena Beck at The Counter.