http://www.sciencemag.org/news/2020/12/common-tire-chemical-implicated-mysterious-deaths-risk-salmon

Particles that erode from tires wash into streams used by coho salmon.

For decades, something in urban streams has been killing coho salmon in the U.S. Pacific Northwest. Even after Seattle began to restore salmon habitat in the 1990s, up to 90% of the adults migrating up certain streams to spawn would suddenly die after rainstorms. Researchers suspected the killer was washing off nearby roads, but couldn’t identify it. “This was a serious mystery,” says Edward Kolodziej, an environmental engineer at the University of Washington’s (UW’s) Tacoma and Seattle campuses.