Science

Yukon River salmon declines: What’s under the surface

Tongass, also known as the Salmon Forest. Photo by Bryan Gregson

And what anglers who value the abundance of these fisheries can do to help

When I moved to Fairbanks, Alaska in 2008 to study for a degree in fish biology, I was mesmerized by the salmon that ascended thousands of miles up the Yukon River and its tributaries to spawn and die, begetting the next generation of these iconic fish.

Driving through Yukon Territory, Canada in late summer I saw a battered but determined bloodred hen Chinook salmon move through the viewing window at the Whitehorse dam on the Yukon River, already 1,745 miles into her upriver journey through both Alaska and Canada.

Yukon drainage coho

Later that autumn, near Fairbanks, I caught my first Arctic grayling under a backdrop of fluorescent yellow birch and aspen, marveling at the carcasses of a dozen chum salmon that ascended more than 900 miles of the Yukon River drainage to reach their spawning grounds.

These were my first glimpses into the world of salmon, and I am not alone in marveling at their magnificence.

Freezer-filling and awe-inspiring fishing in Alaska

As a transplant to Alaska, I quickly became aware of the importance of salmon to the Indigenous Peoples of the region but also reveled in the recreational angling opportunities that salmon offered, directly and indirectly.

I caught and kept a 36-pound King salmon on the Salcha River near Fairbanks, which smoked delightfully despite the long distance it traveled from saltwater. Harvesting this fish, the biggest I had ever caught at the time, was a great source of pride and a healthy freezer-filler for a student with limited means.

Salcha river king salmon

I enjoyed fishing with nymphs and beads for greedy Arctic grayling on the Chena River, lurking downstream of spawning chum salmon. While enumerating coho salmon in a beaver dam-clogged creek, I discovered rare, delicate dwarf Dolly Varden in full spawning colors, a Thanksgiving feast for the eyes.

But the good times were not to last

In 2020, for the first time during my tenure in Alaska, Chinook salmon fishing was closed in the rivers near Fairbanks. Soon after, chum and coho salmon fishing were also closed. These were symptoms of a devastating crash of salmon populations in the Yukon River drainage. Salmon fisheries in the drainage have remained shuttered due to low salmon abundance.

Yukon drainage dwarf dolly

The reasons for salmon run declines are commonly debated but include culprits such as disease, changing ocean conditions and bycatch of salmon in fisheries for other species.

Rural and Indigenous residents of the Yukon River have undergone huge impacts due to the loss of salmon, and there are implications for the recreational fishing community as well.

Cascading effects of salmon declines

Resident freshwater fish prized by sport fishermen, such as Arctic grayling, seek out areas where salmon are spawning and consume stray eggs and bits of flesh from dying spawners. Research from interior Alaska suggests that these “food subsidies” positively affect grayling body condition and boost fat content in late summer, better preparing grayling for the long, harsh winter months during which they primarily live on energy reserves. Grayling that begin the winter with more reserves are more likely to survive until spring, and when spring spawning season begins, they will be able to produce more eggs or milt, potentially resulting in a more productive population.

This is an important consideration in the Fairbanks area, where we boast some of the top Arctic grayling fisheries in Alaska, namely the Delta Clearwater and Chena Rivers, which were, until recently, home to thousands of spawning salmon.  Northern pike, sheefish, grizzly bears, bald eagles, otters, waterbirds and many other animals also heavily rely on adult and juvenile salmon for sustenance.

Salmon bring literal tons of nutrients to river ecosystems

Finally, the marine-derived nnutrients delivered by dying salmon to nutrient-poor freshwater ecosystems boosts productivity of microbial, invertebrate and plant populations in an around streams, echoed in the famous example of the “Salmon Forest” in Southeast Alaska.

With recent salmon declines in the Chena River, for example, a decrease in average Chinook and chum salmon run size estimates from 2004 (9,645 Chinook and 15,163 chum) to 2023 (1,109 Chinook and 821 chum) results in an estimated annual loss of 10,400 pounds (more than 5 tons) of marine-derived nitrogen to the river, an informal calculation based on values from Alaska Department of Fish and Game and NOAA Fisheries publications that assume an average sized 15-pound Chinook would translate to 0.75 lb of nitrogen and average chum to 0.28 lb. In the nearby Salcha River, a similar pattern was seen over the last two decades, with an estimated annual loss of ~24,000 pounds (12 tons) of nitrogen from Chinook and chum decreases annually.

While the salmon problems on the Yukon River are concerning, this is not the only river drainage in Alaska where declines are manifesting. In 2024, for the first time ever, sport fishing for Chinook salmon was closed in all major road system drainages in Alaska: Kenai, Susitna, Gulkana, and Yukon Rivers. Given that, this article is intended as a wake-up call to inform and mobilize recreational anglers who value Alaska’s world-class fishing opportunities for salmon and other species that depend on them.

Chinook salmon

Looking to the future

In David R. Montgomery’s book “King of Fish,” the iterative crash of global salmon fisheries is outlined. These crashes followed a predictable pattern of removal of traditional stewardship, overfishing and habitat degradation. We now have bountiful historical perspectives and the ability to apply that knowledge in Alaska, which holds one of the final bastions of wild salmon.

User groups and industries can use our common interests to produce a unified awareness campaign, voluntary improvements to minimize our negative impacts on the fish and sound initiatives to improve salmon habitat and minimize mortality.

For us anglers, we can help by following fishing regulations designed to protect salmon, buying products from responsible businesses, donating to salmon conservation causes and above all not losing hope nor becoming apathetic.

If we can work to maintain salmon populations in Alaska, it will also benefit resident fish, the associated world-class angling opportunities, Indigenous Peoples, commercial fisheries and our planet. Let’s work together to keep Yukon River and Alaskan salmon populations strong.

Follow along for updates on our work in the Yukon on Trout Unlimited Alaska Instagram and Facebook.