USGS salmon research features at Yukon River Panel preseason meeting

Vanessa von Biela’s studies on heat stress, spawning, and salmon mothers received great attention from U.S. and Canadian leaders.

For Vanessa von Biela, a research fish biologist with the U.S. Geological Survey’s Alaska Science Center, the summer of 2016 passed with a splash of serendipity. 

As she collected samples of spawning Chinook salmon near Tanana, Alaska, babies were doubly on her mind. Her research on adult salmon and their spawn in the Yukon River coincided with her own twin pregnancy. Katie Howard, her co-investigator who at the time was a lead scientist with the Alaska Department of Fish and Game (ADF&G), was pregnant as well.

It was a unique circumstance, von Biela recalls, and one that offered the scientists a heightened connection to the challenges facing the salmon mothers they were studying. Continued analysis of historic Yukon River salmon escapement and water temperature datasets, they found, revealed gaps in long-held assumptions about Chinook salmon mortality. 

“In the world of salmon research, their juvenile phase in the ocean has typically been considered the most critical to their life history,” von Biela says. 

And for good reason — the initial shock of the sea is a daunting physical challenge for young salmon, who are still growing and gaining the strength required to master ocean feeding and avoid predators. Surviving the first few months of marine life is no easy task, and those who do are usually fit enough to persevere through future life stages.

But over the next several years, as von Biela and Howard turned their attention inland to the river, the duo placed a similar emphasis on the latter stages of a salmon’s life — how river conditions impact the health of salmon mothers and, consequently, the next generation of salmon. 

In 2016 and 2017, von Biela and her colleagues collected samples that indicated Yukon River Chinook salmon were experiencing heat stress. In 2019, observers found salmon mothers dying with eggs still inside their bodies when the river was unusually hot. In 2021, a group of Canadian scientists published their finding that salmon mothers were twice as likely to die than salmon fathers when they faced a stressful situation on their spawning migration.

This growing body of evidence encouraged von Biela and Howard to continue their work in earnest.

“We saw very similar relationships in the ocean, as we did with river temperatures,” von Biela says. “Whether it was a warm ocean for the salmon babies or a warm river for the salmon parents, warmth was associated with lower productivity — lower catches of salmon babies in the next generation.”

Salmons’ migration from the Pacific Ocean to their riparian spawning grounds, which covers hundreds to a thousand miles swimming upstream, is already exhausting. This journey is even greater for mothers, who expend large amounts of energy to develop eggs, dig nests, spawn, and guard their young as long as possible. 

The additional challenges of extreme heat and low water levels — induced by warming atmospheric and water temperatures — can overwhelm salmon mothers and are likely a factor in the decline of Chinook populations in Alaska’s longest river. 

“When you’re a Western scientist, you’re taught not to make connections between your own life and what you’re researching,” von Biela says. “But I think we need to be borrowing what we learn in different facets of our life. I’ve been a pregnant adult and a non-pregnant adult. Life is much harder, and energy demands are higher, when you’re pregnant.”

Their conclusions were published in 2023 in the journal Global Change Biology. For von Biela, it is one of many studies she’s completed over the past several years that focus on Yukon River salmon and drought, energy allocation, heat stress, and protein responses. 

Centering adult salmon health in her work, she says, has “dovetailed nicely” with other salmon research that continues to be conducted by the USGS Alaska Science Center, ADF&G, Yukon River Drainage Fisheries Association, and other organizations across Alaska. “There are still open questions about how different stressors shape the salmon population dynamic and trajectory,” she says. 

Earlier this month, von Biela was invited to speak about her work at the 2025 preseason meeting for the Yukon River Panel, an international advisory body established by the Pacific Salmon Treaty that makes recommendations on Pacific salmon management to both American and Canadian leaders. 

The event gathered researchers and Yukon River community members to discuss the year’s escapement projections, highlight restoration projects, and communicate ongoing research and education efforts.

Over the coming months, von Biela will continue several USGS-led studies with collaborators to understand water temperatures and heat stress concerns across Alaska. The work, done in response to subsistence provisions in the Alaska National Interest Land Conservation Act, will likely have wide-reaching impacts for fishers and Indigenous communities throughout the watershed. 

“Why have salmon populations declined in Alaska? That’s the million-dollar question,” von Biela says. “And if we answer that, the next question is: Can we do anything about it?”