Chemical responsible for mass annual coho deaths identified

Our coho have a perilous journey from the Chittenden Locks to the Issaquah Salmon Hatchery — and researchers at the University of Washington, Tacoma and Washington State University, Puyallup have identified the chemical responsible for mass pre-spawning deaths of adult returning coho in our urban streams. 

According to the article, 1% of adult returning coho typically die before spawning. But in these mass death events, anywhere from 40% to 90% perish in the most affected streams.

The article highlights an amazing piece of research and we encourage you to read it. Investigating thousands of potentially lethal pollutants, the research team narrowed it down to just one elusive culprit: 6PPD-quinone, a fish-toxic compound generated by the breakdown of automobile tire particulate. In other words, a chemical preservative found in tire dust is broken down by ozone, creating this highly toxic 6PPD-quinone. This is a remarkable feat of scientific research and determination.

Interestingly, this study suggests that 6PPD-quinone specifically, mortally impacts coho — and not other species of salmon.  

It is worth considering just how quickly this chemical affects adult returning coho as they return to their home streams. 

Researchers call for the development of a “green” chemical alternative to the offending tire preservative. While we agree that better treatment and management of stormwater runoff would also be ideal and should be pursued, it is challenging to implement.

We encourage you to read the article and enjoy their embedded, instructive videos.