For years, researchers have worked to solve the mysterious cause of extreme coho salmon mortality in the Pacific Northwest. A recent study by the San Francisco Estuary Institute and the University of Washington has finally identified the microscopic culprit as a highly toxic contaminant associated with tire particles…The study focused on water samples from the San Francisco Bay area and the Puget Sound in Washington state, but scientists fear the contaminant could affect coho salmon in the Eel and Klamath rivers as well.