At Least 100,000 Salmon In Bristol Bay Died Of Heat Stress in 2019 - Returns Cut In Half Or Worse

Dead salmon on the shores of the Ugashik, Alaska in July 2019. More than 100,000 fish in Bristol Bay were killed by heat stress in 2019. Photo: Birch Block

DILLINGHAM, Alaska (Alaska Public Media) – The sun beat down relentlessly on Bristol Bay this summer, heating up the rivers and lakes where millions of sockeye salmon returned to spawn. July was the region’s hottest month on record, and in some rivers, that heat was lethal. Tim Sands, an area management biologist for the Alaska Department of Fish and Game, estimates tens of thousands of fish died.

“Based on the catch rates we normally see and the escapement we normally see, well over 100,000 fish died in the river,” Sands said. He’s talking about the Igushik River on the west side of Bristol Bay. It’s a long, winding, muddy river in the Nushagak District.


A team examines salmon along the Koyukuk River in July 2019. Photo: Stephanie Quinn-Davidson

By early July, biologists were expecting an average of 15,000 fish to swim upriver every day. Instead, Sands said, “We saw 714 fish go up the Igushik by the tower on July 8. The lack of fish moving up the Igushik River definitely was abnormal.”

Salmon won’t swim through water once it reaches a certain temperature. Water loses oxygen as it gets warmer, and the warmer it gets, the more oxygen fish need. As fish crowd on the bottom of a river waiting for the water to cool, they have less and less oxygen to breathe. Sands said about half a million fish should have escaped upriver to spawn. They only counted half that.


Dead chum salmon line the shore of the Koyukuk River in July 2019. Photo: Stephanie Quinn-Davidson

EDIT

https://desdemonadespair.net/2020/01/record-summer-heat-in-alaska-wiped-out-at-least-100000-kuskokwim-salmon-in-bristol-bay-ive-never-seen-a-salmon-that-is-still-ocean-bright-acting-in-such-a-way.html