Coho salmon are known for their unique life cycle. These fish begin their journey in freshwater, venture into the open seas, and eventually return to their birthplace to spawn. However, over recent years, researchers observed alarming patterns in urban streams of the Pacific Northwest. Many Coho salmon died before they could complete their spawn.

For decades, the mystery behind these deaths persisted. The salmon would display erratic swimming patterns before succumbing to death. Conservationists worried that without identifying and managing the cause, the Coho salmon could face extinction.

An interdisciplinary team comprised of biologists, modelers, community scientists, and environmental chemists took on this challenge. They initially considered several factors like water temperature, oxygen levels, and known toxins. However, none of these factors adequately explained the phenomenon.

Ultimately, attention shifted to chemicals found in tires. The team posited that tire-related compounds might be the primary culprits affecting Coho salmon populations. Identifying the specific chemical responsible remains critical to addressing this environmental issue.

For further engagement, listeners are encouraged to explore other related stories, including satellite monitoring and air pollution’s potential to create superbugs. NPR’s Short Wave provides these insights.

Production credits include Jessica Yung and the editorial oversight of Rebecca Ramirez. The information was verified by Tyler Jones, and Kwesi Lee managed audio engineering.