Multiple Salmon Run Dieoffs Across AK As Water Temps Suffocate 100s Of Thousands Of Fish

[hatrack]

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I’ve worked as both a journalist and a commercial fisherman for over a decade, participating in more than a dozen fisheries from Southern California to the western Gulf of Alaska. I’ve seen booms and busts over the years, and this summer the fishing in Bristol Bay was booming. Estimates say 56.3 million salmon returned to the bay’s rivers. While down from 2018’s record-breaking runs, with 62.3 million fish, Bristol Bay has so far bucked the trend of declining salmon runs seen in other regions. But all is not well. As I was sweating on deck, the water was 18.9 °C—just a few degrees shy of 21 °C, when the temperature starts being lethal to salmon.

Twenty-five kilometers northwest, in the nearby Igushik River, the water was even warmer. One hundred thousand sockeye salmon waited for cooler conditions so they could move upstream to spawn. But, unwilling to pass through the hot, shallow water, the fish used up the available oxygen and suffocated—it was the largest sockeye salmon die-off seen in Bristol Bay, says Timothy Sands, a biologist with the Alaska Department of Fish and Game. Elsewhere in the watershed, temperatures also soared.

On July 4, Anchorage hit 32.2 °C for the first time in recorded history. Six days later, the Cook Inletkeeper, a nonprofit organization based in nearby Homer, announced that salmon stream temperatures were “off the charts,” with water in the Deshka River, northwest of Anchorage, reaching 27.6 °C. In Norton Sound, there was a reported mass die-off of pink salmon. Up the Koyukuk River, a tributary of the Yukon River, there was another heat-related die-off, this time of chum salmon that had yet to spawn.

“I have never seen a summer as extreme as this year,” says Sands, who has worked in the Bristol Bay area since 2002. By summer’s end, Sands and his colleagues saw dead fish in every river in Bristol Bay. The Pebble Mine, a massive open pit gold and copper mine proposed for the headwaters of Bristol Bay, poses a great threat to the world’s largest sockeye salmon run. But a rapidly changing climate and increasingly warm water could be an even bigger problem for the largely untouched salmon grounds. It’s a threat that can seem difficult to reconcile with the recent record-breaking seasons.

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https://www.hakaimagazine.com/news/bristol-bay-salmon-are-in-hot-water/