PORTLAND, Ore. (CN) – Biologists say unusually warm water in the Columbia River spells death for more than 250,000 Sockeye salmon.
June’s record heat combined with an ongoing drought to raise river temperatures more than six degrees, biologists said. Waterways in the Columbia River Basin have been clocking in around 70 degrees.
Temperatures above 68 degrees stress fish during their arduous journey from the ocean to the tributaries where they were born and return to spawn before they die.
In water 74 degrees and higher, the fish stop migrating altogether.
Warmer water makes fish congregate in the few available cool spots. Huddling together increases the exposure to deadly bacteria that the exhausted fish face.
The 2015 migration of Sockeye salmon was unusually large — an estimated 500,000 fish returned from the Pacific Ocean to the Columbia River.
But this year as many as 80 percent of those fish could die, said Ritchie Graves of the National Oceanic and Atmospheric Administration.
Scientists are looking ahead to the late summer migrations of Chinook salmon and steelhead. Management teams are releasing cooler water from the deep reservoirs that dot the Columbia in an effort to keep water temperatures below 70 degrees.
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