I stood on the deck of a fishing boat this past summer, soaked from sweating inside my rain gear after an hour of picking sockeye salmon from our gill net at the mouth of the Nushagak River on Alaska’s Bristol Bay. Fishing is hard enough work, but an early July heatwave sizzled the region, making for grueling conditions on deck. The temperature in southwest Alaska pushed 32 °C. Smoke blowing in from wildfires burning hundreds of kilometers east blotted out the mountains on the northern horizon. Nothing about the conditions was normal.

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. Read more…