Just Keep Swimming… Even Through Wildfires

For tens of millions of years, adult Pacific salmon have been swimming hundreds of miles to return to their birth streams to lay eggs and start a new generation of salmon. However, this journey is now being challenged by climate change, human-created barriers, and the rise in wildfires, like the 2020 Holiday Farm Fire. Follow along as we discover how these fish are faring against the flames.

After traveling over 200 miles, climbing fish ladders to get over waterfalls, and avoiding tantalizing fishing lures from anglers, the Upper Willamette Spring Chinook finally arrived in the McKenzie in May 2020. Following their long journey, the fish spent their summer lazily swimming in pools, fighting over mates, and finding the best spots to spawn in the fall. 

Ignorant of the ongoing pandemic, these salmon had their own problems to worry about. Dams, pollution, and other human activities have decimated salmon populations, reducing the population by 80% over the past century. Climate change contributes to warmer streams across the Pacific Northwest—which is bad news for cold-water fish like salmon.

May turned into June, which turned into July, and then August. Some chinook started spawning while others continued to look for a good spot or the right mate. These salmon had made it upstream despite the barriers, and now they were at the end of their journey. Things seemed good. 

Then the world around their river went up in flames.

Flames from the Holiday Farm Fire surrounded the fish as they spawned, and ash and debris cascaded into the river. It took over a month to completely douse the Holiday Farm Fire, and all that was left were burned trees, dotting the landscape like the black marks on the backs of the chinook. 

Looking at the burned watershed, it was hard to imagine anything surviving in the river, leaving people to wonder what the Holiday Farm Fire meant for the Spring Chinook. Did the chinook even spawn? What would this do to the already threatened population? Did this fire mean extinction? 

Not quite.

In order to understand how fires will affect these fish, we need to understand more about their life cycle.

Spring Chinook are born in the darkness of the gravel nest their parents make and guard to their last breaths. The baby salmon emerge from their eggs, yolk sac still attached, buried in the gravel. As the days get longer, the streams get warmer, and their yolks dwindle to nothing, the salmon emerge from the gravel. Some juveniles migrate to the ocean in their first summer (sub-yearlings) while others stay in the river, fueling up on insect larvae, plankton, and detritus until the following spring (yearlings). Both sub-yearlings and yearlings follow the flow of the McKenzie to where it meets the Willamette just north of Eugene, down the Willamette until they reach the Columbia in Portland, and out to the Pacific. 

They spend a few years in the ocean and then find their way back to the mouth of the Columbia as early as February, set to return to their birth stream. 

The Upper Willamette Spring Chinook swim through Portland and Salem before making their way to the McKenzie just north of Eugene. They spend the summer in deep pools, away from the eyes of people, before finally spawning in September.

They dig nests in the gravel by beating their tail fin against the ground over and over, ignoring the wounds and rot they sustain as a result. The females lay their eggs, and the males fight to be the ones to fertilize them. Then the eggs are covered, and the adult salmon die soon after, guarding their nests until the end. Their bodies provide nutrients for the streams, feeding the insects and larvae their children will consume in a few months.

It’s hard to see images of the Holiday Farm Fire—flames surrounding the McKenzie, smoke billowing across Oregon, debris cascading into the river—and not assume wildfires will harm salmon. And they can; large wildfires increase the risk of erosion which can lead to landslides that suffocate nests. The juvenile yearlings in smaller stems can be buried in ash and debris. Large trees that once provided shade for streams burn down, leading to a potential rise in stream temperatures.

However, Rebecca Flitcroft, a Fish Biologist for the US Forest Service in Oregon, says wildfires are much more likely to help Spring Chinook in the long run despite how terrifying the fires might look.

“Salmon are used to wildfires and highly adaptive, so the complexity and habitat diversity that wildfires create can actually benefit them,” says Flitcroft. Wildfires burn down trees, leading to more large woody debris in streams. This debris creates deep pools of slow-moving cool water—perfect for Spring Chinook who need a place to spend their summers. Wildfires also lead to more food possibilities for juvenile salmon. 

Flitcroft also notes that water temperatures and erosion during a fire are generally not a problem because salmon are mobile, saying “as long as they aren’t in a narrow sidestream, they can easily move to cold reservoirs even if stream temperatures increase.” Similarly the salmon can avoid debris and landslides from the wildfire fairly easily, and spawning salmon were largely unaffected by the Holiday Farm Fire. Dams and similar barriers are much more dangerous to salmon than even severe wildfires, Flitcroft says.

Spring Chinook fry emerged from the McKenzie gravel in early 2021, having survived any ill-effects of the fire. Some migrated to the ocean last summer while others just migrated this spring, ready to begin their lives as adults alongside many students in nearby Eugene graduating from high school and college. 

Even in the face of devastating fires, salmon have proven they are resilient and adaptive. They’ll take stream restoration whether it comes from humans or fires. When streams become uninhabitable, they’ll find new ones. In a world changing rapidly, salmon like the Upper Willamette Spring Chinook are a symbol of adaptability and hope in the face of climate change. However, as more and more problems build up for the fish—ocean acidification, warming streams, dams, low streamflows—the world may change too fast for these populations to keep up. As humans, we need to rise to the challenge of mitigating and fixing the problems that we have caused for the salmon so that they have the chance to adapt and survive.

This is an interactive map of past and ongoing restoration projects on the McKenzie Watershed overlaid with the outline of the Holiday Farm Fire. Click here or on the map to interact with this map and learn more about these projects. Made by Jenna Travers.