CHICO — Spring-run chinook salmon, native to Butte Creek, Deer Creek and Mill Creek, whose populations reported sharp declines in the 2023 season as a result of recent drought years, are being taken to UC Davis in an “urgent action” to conserve their genetics.
Biologists began early October making trips to capture juvenile fish before they head towards the ocean at Deer Creek, where fewer than 25 adult salmon returned this year, said Peter Tira, information officer for the California Department of Fish and Wildlife.
“This is the first time we’ve ever done it with spring-run salmon, where we bring them into a hatchery environment to kind of safeguard the population in case it disappears in the wild,” Tira said.
While at UC Davis, the fish will be staged at the university Center for Aquatic Biology and Aquaculture for the next two years until a new home is found for them.
“The plan is not defined at all. We’ve never done this before with spring run, and so we don’t have a real long term plan thought out at the moment, we have to develop it,” Tira said. “But what we had to do is act to get some fish, just in case this population goes extinct.
“Hopefully we never have to use these fish. The salmon have shown a remarkable ability to kind of rebound; various environmental disasters and challenges and things like that. But in case they don’t, we have a population of fish,” he said.
Both Deer and Mill creeks reported fewer than 25 adults returned in the 2023 season, and Butte Creek reported 95 adults — the lowest count since 1987 by all measures, and the lowest count since 2001 by a standardized snorkel method, according to Tira.
Fall-run salmon and trout species have historically been taken for conservation in the past, but a phenomena field biologists call “cohort collapse” is now critically affecting spring-run salmon in the central valley, prompting the emergency conservation effort.
The drought from 2019 to 2022 in California, according to a statement from CDFW, led to a sharp decline in adults returning from the ocean to the three creeks.
And while chinook salmon have 3- to 4-year life cycles that gives the species resiliency against catastrophic events for single-year classes, the multi-year drought appeared to have a compound effect on the salmon’s ability to survive extirpation, the statement said.
“Not only does the population decrease, but you have so few fish spawning you have very limited genetic diversity. So we’re trying to collect as much genetic diversity so we can keep it in our back pocket,” Tira said.
Tira said Butte Creek is monitored by biologists year round, and that yearling fish will be taken later in the month in the area.
“It’s a big priority given its importance, and of the three creeks we mentioned, Butte Creek has produced the most salmon,” Tira said.
Matt Johnson, senior environmental scientist supervisor for the CDFW northern region, worked on capturing fish in upper Deer Creek on Oct. 10.
“We estimate there are 25 that return to Deer Creek this year, and that’s a warning sign for us,” Johnson said. “It’s a time to take action so we can have an insurance policy — if we have a couple more really bad years — we can have a captive brood population that we can use to start a conservation hatchery and make sure these fish don’t blink out.
“They’re at the point where they need a little help from us.”
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