State and federal wildlife officials this month are preparing extraordinary measures to protect Chinook salmon returning to spawn in California’s drought-depleted rivers.

Sacramento River fall-run Chinook salmon are making their way upstream from the Pacific Ocean to begin their annual spawning ritual. These fish, primarily produced in hatcheries, make up the most abundant salmon run in California and are the primary catch for an ocean fishery that sustains thousand of jobs.

But the species has had wild population swings over the past decade because of droughts, poor ocean conditions and loss of habitat. Officials are hoping to avoid another wild swing by taking action to help this year’s run, including some measures that have never been tried in California.

At the American River Hatchery near Sacramento, the California Department of Fish and Wildlife is installing water chillers at a cost of nearly $1 million to ensure water coursing through the hatchery doesn’t become lethally warm for salmon and other species hatched and raised there. The chillers, essentially giant refrigeration units, are in place at a few hatcheries around the state but had never before been used on the American River.

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