We covered this back in July, but the Seattle Times just released an article on Wednesday that highlighted the problem once again: stormwater is killing coho salmon before they can spawn. It’s called pre-spawn mortality, and it’s a surefire way to push extinction along.

The bad news is that it will continue. Here’s why:

In the Pacific Northwest, it’s sunny and dry all summer long, well into September.

During the dry season, all of the oil and grease and tire dust and brake fluids…not to mention pet waste, pesticides, herbicides, and so on…are deposited on driveways, streets, and parking lots.

All of that debris builds up, and it’s highly toxic.

It starts to rain in late September/October. The first rains carry the highest concentrations of toxins as stormwater runoff into our lakes, river, and streams.

Coincidentally, our coho salmon swim upstream to spawn at exactly the same time.

Within hours of coming into contact with the stormwater, the female salmon die, often before they spawn, resulting in extinction in urban streams. No spawning means no new generation of salmon.

The good news is that we are taking steps to fix it. Installing green stormwater infrastructure, protecting riparian systems, and tracking and prioritizing locations with the highest runoff and biggest impacts helps.

But it takes all of us to pitch in, because in cases of extinction, and the loss of a culture, it is too great of a risk to stand by and hope someone else does it first.

So plant a rain garden. Take care of your car. And pick up after your pets. You’re not just saving money and peace of mind. You’re saving our history and protecting our priceless resources.


  • http://your.kingcounty.gov/dnrp/library/water-and-land/science/seminars/October-2007/pre-spawn-mortality-of-coho-salmon-in-restored-urban-streams.pdf
  • http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12534/full
  • https://www.seattletimes.com/seattle-news/environment/stormwater-pollution-in-puget-sound-streams-killing-coho-before-they-can-spawn/

About the author

Erin Rothman

Talk stormwater with erin@stormsensor.io With more than 15 years of environmental consulting experience, Erin observed so many opportunities for innovation in the stormwater industry. With those in mind, she founded StormSensor to enthusiastically embrace new technology to help solve the problems of an age-old industry.