Warming rivers in Alaska threaten Chinook salmon populations and Indigenous food security

(Press-News.org) For millennia, Indigenous people living in Alaska and Canada’s Yukon territory have relied on Chinook salmon. The large, fatty fish provide essential nutrients for Arctic living and have influenced traditions and languages across generations.

But over the past three decades, many communities have been unable to fish Chinook amid a sharp salmon population decline.

The situation could worsen as climate change warms rivers in the Arctic, stunting salmon growth, according to a study published August 6 in Scientific Reports led by the University of Colorado Boulder.  

“The fish are really important for maintaining the culture and language of Indigenous communities,” said Peyton Thomas, a research associate at the Institute of Arctic and Alpine Research. 

In collaboration with locals on the ground, the team is now working to help communities prepare for the changes ahead.

Over the past 50 years, the Arctic has warmed nearly four times faster than the global average. Climate change has melted sea ice, thawed frozen ground and eroded coastlines, reshaping the Arctic landscapes Indigenous peoples have called home for generations.

Prior research has suggested that increased river temperatures can affect fish species adapted to cooler environments. Chinook salmon in the Arctic are a prime example. One study estimated that Chinook salmon populations in the Yukon River, Alaska’s largest, plummeted by more than 57% between 2003 and 2010. 

Working closely with Indigenous communities in Alaska, Thomas and her team set out to better predict how climate change would affect fish populations in the seven river basins spanning watersheds in Alaska and Yukon. 

After talking to tribal members, the team focused on two species important for subsistence, Chinook salmon and Dolly Varden, a type of trout.  

Using computer models, the team simulated how the region’s climate and rivers might change by mid-century. They found that summer river temperatures could rise by 1.26 °C (2.27 °F) by mid-century compared to the average between 1990 and 2021. 

When they combined these data with a fish growth model, they found that in the warmest future years, four out of seven river basins would experience water temperatures surging above what juvenile Chinook salmon can tolerate. 

On the other hand, Dolly Varden thrive in slightly warmer water than Chinook salmon. The simulations suggested that these fish might nearly double their growth in many rivers.

“It is good news that not all species are going to decline under warming,” Thomas said. “But communities have different preferences about fishing Dolly Varden. We’re trying to show that maybe in warm years, Dolly Varden could be an alternative.”   

This study comes just a year after Alaska and Canadian authorities agreed to pause Chinook salmon fishing, both commercial and subsistence, for seven years in a bid to allow their populations to recover. 

“The coolest part of this work is just being able to see how we're all trying to connect with each other,” Thomas said. “We learned so much from history and people's daily lived experiences in these places. Everyone should be a part of all of this work, because we can't do it just by modeling.” 

 

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