Coho Salmon Mortality and Tire Chemicals

In the Pacific Northwest, Coho salmon have faced a mysterious threat for decades. Many of these salmon were found dead in urban streams before spawning. Without intervention, researchers feared the species might face extinction.

Coho salmon have a distinct life cycle. They spawn in freshwater, migrate to the sea, and later return to their birthplace for reproduction. However, some die unexpectedly before completing this cycle. Observational data indicated these salmon were often seen swimming erratically before death.

To identify the cause of these premature deaths, a dedicated team of biologists, environmental chemists, modelers, and community scientists embarked on an investigation. Initially, they examined typical environmental factors like water temperature, oxygen levels, and known toxins, yet found no answers.

The research team eventually focused on chemicals associated with automobile tires as potential culprits. Despite narrowing down the possibilities, determining the specific chemical responsible remained challenging.