The California Department of Fish and Wildlife (CDFW) and National Oceanic and Atmospheric Administration (NOAA) Fisheries biologists are pursuing urgent measures in northern California this fall to save some of the last remaining Central Valley spring-run Chinook salmon after the numbers returning from the ocean this year fell sharply toward extinction.
Biologists call this year鈥檚 sharp decline a 鈥渃ohort collapse鈥 because so few threatened adult spring-run Chinook salmon returned to the small streams still accessible to them. Mill and Deer Creek 鈥 two of the three streams that hold the remaining independent spring-run populations 鈥 each saw fewer than 25 returning adults this year. Returns to Butte Creek 鈥 the third independent population 鈥 were the lowest since 1991, and adults further suffered impacts of a canal failure in the watershed. These creeks are tributaries to the Sacramento River.
鈥淲e are running out of options,鈥 said Cathy Marcinkevage, assistant regional administrator for NOAA Fisheries West Coast region. 鈥淲e want this species to thrive in the wild, but right now we are worried about losing them.鈥
Housing captive broodstock
Central Valley spring-run Chinook salmon typically follow a 3- or 4-year life cycle, a strategy that provides some resilience to catastrophic events occurring to an individual year class. While other year-classes (or cohorts) will return in coming years, the 2019-2022 drought impacted multiple cohorts, increasing risks for extirpation.
Biologists will capture juvenile fish from Mill, Deer and Butte creeks to start a conservation hatchery program that will safeguard the genetic heritage of the species.
新澳门六合彩内幕信息 Davis will house the captive broodstock at the University鈥檚 Center for Aquatic Biology and Aquaculture (CABA) for the next two years until a longer-term facility is identified.
鈥淚t鈥檚 a privilege to work with this species, and I鈥檓 glad we have facilities and expertise that can help,鈥 said Nann Fangue, 新澳门六合彩内幕信息 Davis professor of fish physiological ecology and director of CABA. 鈥淢y staff, the students and our partners are all really dedicated to this work and to the goal of conserving native species.鈥
Conservation hatcheries are vital to the protection and recovery of other highly imperiled salmon stocks, including endangered Sacramento River winter-run Chinook and Central California Coast Coho salmon.
鈥淭hese drastically low returns come at a time when we鈥檝e already been taking extreme measures to protect salmon strongholds and eliminate existing barriers keeping them from their historic habitat,鈥 said CDFW Director Charlton H. Bonham. 鈥淲e鈥檝e got to continue to do everything we can to preserve these iconic fish.鈥
The remaining populations of spring-run Chinook are declining more than 10% each year and face high risk of extinction, according to an by NOAA Fisheries鈥 Southwest Fisheries Science Center. One population initially benefited from strong adult returns in 2021, but more than 90% of the fish died prior to spawning when high stream temperatures exacerbated by thiamine deficiency and wildfires fueled a disease outbreak in 2021.
Cold-water fish need cold water
Central Valley spring-run Chinook also face high risk from climate change since dams have cut off much of the high-elevation habitat where they once spawned in cold mountain rivers. Their survival in lower elevation habitat often depends on releases of cold water from reservoirs that face competing demands for their limited volume of water.
It鈥檚 a privilege to work with this species.鈥擭ann Fangue, 新澳门六合彩内幕信息 Davis
鈥淭hese cold water fish need cold water, and that is going to become more limited in California鈥檚 climate future on the Valley floor,鈥 said Rachel Johnson, research biologist at NOAA Fisheries鈥 Southwest Fisheries Science Center and lead author of the spring-run viability analysis. Their survival in the high temperatures of lower elevation habitat often depends on releases of cold water from reservoirs that already face competing demands.
Scientists will strive to maintain the genetic diversity of the species through the hatchery broodstock program. As the instream flow requirements and habitat restoration efforts improve the odds of the fishes鈥 survival in the wild, biologists could use hatchery offspring to restore genetically diverse and locally adapted populations of spring-run Chinook in California鈥檚 rivers.
Media Resources
Jordan Traverso, CDFW Communications, (916) 212-7352
Michael Milstein, NOAA Fisheries, (971) 313-1466
Kat Kerlin, 新澳门六合彩内幕信息 Davis News and Media Relations, (530) 750-9195
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