California’s winter-run Chinook salmon population rebounded significantly this year, federal officials said Thursday, providing hope that the species can be saved from extinction even as the drought continues.
The health of the winter-run salmon, which are protected by the Endangered Species Act, has major implications for California’s drought management policies and the way water is allocated to Central Valley farmers. The fish have been decimated by the drought, and reservoir managers have been curtailing deliveries to farms in an effort to keep the species alive.
Figures released Thursday by the federal government suggest those efforts are helping. About twice as many winter-run salmon have been counted on the Sacramento River so far this year compared to 2015, and the percentage of fish killed by river conditions has fallen considerably.
The total number of fish remains small by historical standards, however.
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“This species has a long way to go in terms of viability,” said Maria Rea, assistant regional manager at the National Marine Fisheries Service.
The winter-run salmon depend heavily on having cool water – 56 degrees or lower – on the Sacramento River. If the temperatures get too high, the eggs and the juveniles bake to death. Despite their name, the fish spend much of their young lives in the Sacramento River during the summer before heading out to sea in the fall.
In an effort to maintain the population, the U.S. Bureau of Reclamation has been holding additional water back at Shasta Lake during the spring, trying to keep the reservoir cool, and releasing that water later than usual into the Sacramento River. The idea was that the water in the river would be cool as the adults returned to spawning grounds below Shasta Dam.
The plan largely failed in 2014 and 2015, with only 5 percent of juveniles surviving in 2014 and 3 percent last year. Meanwhile, farmers were angry because they weren’t getting a lot of their irrigation water delivered when they needed it.
Because the Chinook have a three-year spawning cycle, executing this year’s temperature plan was considered critical to keeping the species alive. The bureau settled on a plan that called for an uninterrupted flow of water to farmers while closely monitoring water temperatures in the reservoir. Officials pledged to keep more water longer in Shasta if temperatures rose too high.
Rea said the plan worked, and temperatures stayed below 56 degrees while farmers didn’t see any delays in deliveries. “We’re declaring success on maintaining temperatures,” she said.
Yet the salmon population is still fairly low – less than half what it was in November 2010, for example. The reason is that far fewer adults returned to spawn this year. Those that did return were smaller than usual and laid far fewer eggs. Those problems are likely a result of the drought-related stress on the species, said Garwin Yip, branch chief for water operations at the fisheries agency.
Salmon fishermen said they were pleased that the population improved but are still worried about the species’ future. “They provided better conditions for this year, no doubt about it, they kept the water cooler,” said John McManus of the Golden Gate Salmon Association, which represents commercial fishermen.
But he added, “We’re not out of the woods yet.”