NORTHERN CALIFORNIA—As many as 3.8 mullion juvenile winter-run Chinook salmon trekked from the Sacramento River in the Central Valley to the Pacific Ocean in 2019, according to NOAA Fisheries – the highest number in a decade for the endangered fish.
Nearly 5 million juvenile winter-run Chinook salmon made the trip down the Sacramento River and toward the Pacific Ocean in 2009, the last time this many of the species made the trek.
NOAA Fisheries added an estimated 8,000 adult fish made it back to the Sacramento River this year for spawning, the highest number since 2006.
“This year’s generation of juvenile winter-run Chinook salmon is considered especially critical because two years’ worth of naturally produced winter-run Chinook salmon offspring were almost entirely lost in 2014 and 2015 during California’s severe drought,” NOAA Fisheries staff stated in a released report on Dec. 6. “That left few juvenile fish to migrate to the ocean in those years and return as adults to spawn.”
Winter-run Chinook salmon thrive in cold-water rivers of Northern California. The species’ long-distance migration, however, was essentially cut off when the Shasta Dam was completed in 1945.
“The fish were then forced to spawn instead in the exposed main channel of the Sacramento River below the dam, far from their historic cold-water habitat, in the summer where they are vulnerable to high temperatures that can stress and kill their eggs,” NOAA Fisheries staff stated. “Biologists and water managers coordinate the storage and release of cold water behind Shasta Dam to cool the river downstream and help the fish and their eggs survive the hot summer months. After the losses in 2014 and 2015, they took additional measures in 2016 to conserve the cold water for use later in the summer.”
Seasonally cold water released from the Shasta Reservoir has helped the single remaining population of winter-run Chinook salmon survive in the Sacramento River.
Federal officials tried to help the endangered Chinook salmon in 2014 and 2015, releasing a combined 1 million of the species from the U.S. Fish and Wildlife’s Livingston Stone National Fish Hatchery during those two years to supplement critically low numbers of the winter-run fishery.