New Indicators Anticipate Rising Challenges for California Chinook Salmon and Fisheries, Research Finds

Two decades of warming rivers, drought, and shifting ocean conditions have coincided with declines in California's Chinook salmon populations. This signals an uncertain future for one of the state's leading commercial fisheries-and the fleet that depends on them.

New NOAA Fisheries research links the stressors affecting juvenile salmon, including warm freshwater temperatures and low streamflows, to reduced adult salmon returns. Low returns closed commercial California salmon fishing for 3 years starting in 2022. While fishing resumed this year, the study published in the Canadian Journal of Fisheries and Aquatic Sciences describes key indicators likely to continue affecting salmon abundance.

The indicators can help managers take steps to improve salmon survival and reduce constraints on fisheries to meet administration priorities to extend Pacific salmon fishing. That will help fulfill the 2025 Executive Order: Restoring the Competitiveness of American Seafood .

"There are still dials we can turn to get more fish out there and improve fishing opportunities," said Regional Administrator Jennifer Quan.

Environmental stressors affecting salmon can compound previous impacts , scientists said. "Almost two centuries of human modifications to habitat and salmon genetics act as force multipliers for negative effects of those stressors," said Stuart Munsch, a fisheries biologist at NOAA Fisheries' Northwest Fisheries Science Center in Seattle and lead author of the new research.

The research grew out of annual Ecosystem Status Reports from NOAA Fisheries' two West Coast laboratories that assess the outlook for fisheries. Scientists set out to identify biological and physical indicators that best predict the success of three California salmon stocks:

• Sacramento River fall Chinook
• Central Valley spring Chinook
• Klamath River fall Chinook

Forecasting Fisheries

The two fall Chinook species form the backbone of California and Oregon ocean Chinook salmon fisheries. Accurate indicators help estimate future salmon survival and returns, guiding the Pacific Fishery Management Council in planning potential seasons and harvest levels, said Susan Bishop, who leads the Salmon Management Branch in the West Coast Region.

The indicators can also inform restoration and other actions to reduce risks to salmon, increase their survival, and anticipate impacts on coastal communities, she said.

"We're not there yet, but this study shows there is promise to improve forecasts with indicators," added Correigh Greene, senior scientist at the Skagit River System Cooperative who coauthored the research while previously at the Northwest Fisheries Science Center.

The West Coast Region is also looking toward salmon conservation goals, such as returning endangered winter-run Chinook salmon in the Sacramento River to their original mountain spawning streams. These streams are currently blocked by Shasta Dam. Trials starting in 2022 demonstrated reintroduction of the species to the cold McCloud River. Shifting the spawning grounds of the endangered species out of the mainstem Sacramento River would open new options for water management and boost fall Chinook salmon that support ocean fisheries.

Dashboard for Survival

Scientists identified indicators with the strongest connections to the success of the California runs, including:

• The number of naturally spawning Central Valley spring and Sacramento River fall Chinook salmon
• Water temperatures during egg incubation of Central Valley spring Chinook and migration to the ocean for juveniles of all three species
• Suitable river flows as juvenile salmon in the Sacramento River migrate downriver
• The abundance of alternative prey species such as juvenile rockfish that buffer Sacramento River fall Chinook from ocean predators
• The phase of the North Pacific Gyre Oscillation , a climate pattern that drives upwelling of nutrient-rich ocean waters benefiting the Central Valley spring and Klamath River fall Chinook

Declining natural spawners, increasing river temperatures, droughts, a long negative phase of the North Pacific Gyre Oscillation, and increased predation pressure in the ocean have coincided in the last two decades with lower salmon recruitment. That means fewer young salmon survived to join the adult population.

Cool river conditions especially have become more important as cold water has grown scarce in recent decades, the research found. The deteriorating conditions may explain why California Chinook salmon-at the southern end of the species' distribution-fared worse than salmon in cooler areas such as the Northwest.

Klamath River fall Chinook were considered overfished for return years 2017-2024. They were no longer overfished as of 2025 but continue to rebuild, while Central Valley spring Chinook are listed as threatened under the Endangered Species Act. Many salmon fishermen supported the recent salmon closures, sacrificing earnings to give salmon time to rebound.

Restoration such as beaver dam analogues and other low-cost improvements can improve the resilience of salmon populations. Targeted water management can also improve flows when salmon are most vulnerable. The removal of four dams on the Klamath River also reopened hundreds of miles of river habitat , boosting salmon survival and numbers. The West Coast Region works with federal, state, and tribal partners in the Klamath Basin to support salmon populations. Our actions reduce regulatory burdens and uncertainty for water users, improve the health of the ecosystem, and uphold tribal trust obligations.

Since salmon stocks listed under the Endangered Species Act mix with others in the ocean, managers may limit fishing to protect low numbers of listed fish. Habitat improvements can improve their abundance , though, relieving the limits and creating more flexibility for commercial and recreational fisheries to continue and and even expand.

Fleet Faces Challenges

The indicators are more than science metrics; they also affect the fishing fleet. Reduced runs and increasing costs have taken a toll on fishing communities such as Eureka, Fort Bragg, and Bodega Bay, Bishop said. In 1984, more than 2,500 vessels fished for salmon off California. Just 470 participated in the most recent full year of fishing in 2022, according to the California Department of Fish and Wildlife.

"This is real hard on people and their communities. It's not just about the money; fishing is identity-it's part of who fishermen are," Bishop said. "People will get out of the fleet because it just doesn't make economic sense for them anymore, and those effects will ripple throughout the community."

The California salmon fleet received more than $20 million in federal emergency relief following each of two disaster determinations for the Sacramento River and Klamath River fall Chinook fisheries in 2023 and 2024 . Disaster funding is a last resort, though. The better solution is to increase salmon abundance and fishing opportunities, she said.

Researchers stressed the value of continuing to track indicators to understand further changes in salmon abundance, and watching for new indicators of salmon performance.