Experts fear if elevated water temperatures continue, the fish species could be driven to extinction.
The California Department of Fish and Wildlife said the water is so warm that young salmon may not make it.
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Officials said salmon eggs are also at risk.
"Their eggs will be laid in water that is too hot. And those eggs will die," said John McManus, president of Golden State Salmon Association.
But things are being done to help the salmon population, such as relocating them directly to the ocean.
Fish and Wildlife officials also recently relocated hatchery salmon instead of releasing them into the Klamath River.
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Gov. Gavin Newsom is calling for Californians to voluntarily reduce their water usage by 15% to protect water reserves to help maintain critical flows for fish and wildlife.