Is runoff killing Edmonds salmon?

It’s not easy being a salmon.

From the moment these fish hatch until they return to their home streams to spawn, they run a hundreds-mile-long gauntlet rife with hazards including salmon-loving predators like Orcas and sea lions, sport and commercial fishing operations, dams and other barriers to migration, pollution and warming ocean temperatures, to name a few.

Driven by instincts deep in their DNA, salmon return from their years-long ocean journey ripe with eggs. They enter their home streams compelled by a single-minded purpose: to spawn and complete their life cycle.

But for many salmon returning to western Washington streams, the journey ends very badly.

As if their long twisted odyssey weren’t enough, researchers have found a new threat hiding in the waters of their western Washington spawning streams — a combination of deadly toxins. Swimming through this chemical stew, the fish become disoriented, turn belly up and die before they can complete the final ritual that gives rise to the next generation of their kind and ensures the survival of the species.

The culprit: toxic runoff.

Finding that stormwater is “unusually lethal” to adult Coho returning to spawn, a group of National Marine Fisheries Service/NOAA scientists working out of the Seattle NOAA Center on Portage Bay embarked on a study to see how this is playing out in our local waterways. Using 51 spawning sites in the Puget Sound basin, they considered a host of factors that affect runoff quality including patterns of land use and land cover, amounts of impervious surfaces, human population density, roadways, traffic intensity, and annual summer and fall precipitation patterns.

According to the researchers, the problem of toxic runoff is particularly acute for Coho salmon, a sentinel species in freshwater communities and a species of concern under the U.S. Endangered Species Act. Coho have the misfortune to be far more sensitive to pollutants than their Chum and Chinook cousins, and are being hit the hardest.

Think of Coho as the canary in the coal mine.

One example: the scientists exposed hatchery Coho to runoff collected from Highway 520 near Montlake. All of them died. Every one.

The paper by principal researcher Blake Feist and various associates sheds light on factors associated with and contributing to polluted stormwater and its devastating effects on salmon spawning areas in the Puget Sound basin. Their work has caught the attention of local fish biologists, environmentalists and the general public, and was recently featured in a story written by environmental reporter Lynda Mapes from our online news partner The Seattle Times.

The researchers report that the sweet Northwest rainwater that traditionally feeds our streams and creeks is increasingly a thing of the past. In many places our surface water has become a complex chemical mix spiced with motor oil, brake pad dust, pesticides, herbicides, antifreeze, fertilizers, tire dust, detergents and a myriad other substances picked up from our streets, lawns, homes, parking lots and rooftops.

Their initial findings: Coho die in greater numbers where there are more impervious surfaces, roads and traffic, and that the highest death rates are associated with rainy periods in summer and fall when rains wash the accumulated mix of chemicals and particulates into our waterways. In some local streams the researchers predict that more than half the salmon will die before they spawn.

After running these data through their admittedly complex computer program, the researchers came up with a model to predict salmon mortality in other areas across the Puget Sound basin based on traffic, road and rainfall patterns. From this, they developed maps breaking down the region into areas where they expect mean mortality of returning Coho to be less than 10 percent, between 10 and 40 percent, and greater than 40 percent.

Predicative map for Edmonds, courtesy of Blake Feist, NOAA

They caution that these numbers are the result of a complex model using varied sets of data, and that in any given year could vary widely from their predictions due to fluctuations in rainfall, traffic patterns, and a host of other variables. Most importantly, the predictions are based on factors contributing to runoff that are statistically associated with higher levels of salmon mortality, not the actual toxins that are killing the fish.

But when applied to Edmonds salmon streams, the numbers are concerning, showing a predicted mean mortality rate for returning Coho as between 30 and 40 percent in Shell Creek, and a troubling 40-plus percent in Shellabarger.

Joe Scordino (right) and members of the Edmonds-Woodway High School Students Saving Salmon club look for returning salmon in Shell Creek. (Photo courtesy of Joe Scordino)

Edmonds’ Joe Scordino has been in the middle of our local salmon situation for years. A retired fisheries biologist, Scordino works closely with the Edmonds-Woodway High School Students Saving Salmon club, and is seen as an expert on the topic. Over the past few years he and the students have overseen and conducted several streambank restoration projects and water quality analyses, counted returning salmon, and released hundreds of hatchery salmon into our local waterways, all in an effort to help restore Edmonds’ once-plentiful salmon runs.

“There’s no doubt in my mind that runoff is a major factor affecting salmon in our community,” Scordino said. “It’s a staggering problem really, and the NOAA study only scratches the surface.

“Runoff is a complex stew of chemicals from a myriad of sources,” he continued. “Take just one — tire dust. No one really knows what it’s composed of and in what proportions. It’s never been studied. The same goes for the host of other chemicals present in runoff. And then how do these various chemicals interact once they’re in the stormwater? Are there synergistic effects? Is the whole more toxic than the sum of its parts? Do they react with one another in a way that makes the stew more toxic? And finally, what part of this brew is actually killing the fish?”

As a start, Scordino and the students have done chemical sampling of streams in Edmonds, sending the samples off to an Everett-based lab for analysis.

“We’ve been collecting water samples from our streams and in and around the marsh for two years now and having them analyzed,” he reports. “We’ve found levels of polycyclic aromatic hydrocarbons (PAH’s), a recognized carcinogen, that exceed EPA standards. The highest levels we’ve found are where runoff from Highway 104 drains directly into the marsh, which suggests to me that the researchers are going in the right direction correlating roads and traffic with salmon mortality.”

With the fall spawning season in full swing, Scordino and the students have been monitoring salmon returns in Shell Creek and other local waterways, and asking the public to help by reporting any salmon sightings.

“So far it’s been disappointing,” he says. “We’ve found one dead Coho and a few chum. The Coho showed clear signs of predation (meaning it was killed by a predator, like a raccoon or coyote), so we’re pretty confident that this was not a case of pre-spawn mortality. Historic records from the last century suggest fairly robust runs, but these are all anecdotal and don’t give a quantifiable picture of how things used to be. But just knowing they were there gives us the impetus to work to restore them.”

Scordino freely admits that we need to know more to better target local salmon restoration efforts.

“We’re starting to get a picture of where the toxins are coming from,” he adds. “It would be easier to address if it came from a point source like a leaky oil tank, but stormwater is a moving target. It has no single source, and the mix of chemicals it carries varies with the season, rainfall, traffic and land use patterns. It’s maddeningly complex, but knowing what these toxins are, which ones are killing the fish, and where they’re coming from is critical to directing any kind of effective salmon restoration.

“I wish it were a simple solution,” he concluded. “But this just isn’t one of those.”

— By Larry Vogel

5 Replies to “Is runoff killing Edmonds salmon?”

  1. I’d love to know your thoughts on the neighborhoods near the water that are on septic systems. I happen to live in one of these neighborhoods in unincorporated Snohomish County (between Edmonds and Mukilteo) and know it has a negative impact on Puget Sound and the salmon (and thus the orcas as well). Do you know if there has ever been a push to convert these neighborhoods to a local sewer system? I did try to bring it up within the community, but there is definitely resistance.


  2. How do you know that septic systems are doing the damage? Its seems more likely that the runoff from the streets making its way into streams is more demonstrably damaging.


  3. National Geographic, years ago, had an article about cleaning up toxic sites using trees. The chemicals would be drawn up through the roots to the leaves where the sun would, apparently, break down those chemicals. Not sure how this would work in the land of rain but it might be worth investigating. The people interviewed for the article were named and research referenced.


  4. I have been wondering about the toxic asphalt that was put on our street 2nd Avenue North a couple years ago. We have cleaned up BUCKETS of this toxic material that did NOT stick to the asphalt……the tiny rocks with the toxic asphalt on it. I am assuming that so much was washed right to the water here. I believe there is still some coming up as we can still see it. It so shocking that government officials here do not seem to give a you know what about our aquatic life………Particularly the SALMON!! Many can attest to trying to sweep up this asphalt rock before it gets in the system……….


  5. I wonder if a selective breeding program could be undertaken, which would produce coho that are more resistant to storm run-off. Then the rivers could be stocked with these resistant fish just like what is already being done. That’s obviously not a permanent solution even if it’s not a ridiculous idea, but it has worked in conservation of other plants and other animals. The long term strategy is to reduce pavement so that water can leach. There’s less urban sprawl in Europe because older cities evolved before planners started zoning/planning. In the US, commercial is zoned over ‘there’ and home is zoned over ‘here’, and we use cars to get from ‘there’ and ‘here’. European cities initially evolved more organically with little to no planning, meaning less roads, more mixed use buildings, more public transit and walking; thus less cars and less toxins in run-off. The irony of advocating selectively bred fish to deal with our selectively bred transportation system.


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