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Photo: NOAA/FIS
NOAA: El Niño Yields to Upwelling in the California Current, Renewing Productivity of West Coast Ecosystem
UNITED STATES
Wednesday, March 12, 2025, 00:10 (GMT + 9)
Outlook for salmon improves after low returns closed California fisheries.
According to the NOAA California Current Integrated Ecosystem Assessment’s annual report, the California Current Ecosystem pulled out of a strong El Niño pattern in 2024.
Map of most sampling efforts in the California Current Ecosystem (CCE) and U.S. west coast Exclusive Economic Zone (EEZ). Symbols indicate hydrographic line sampling stations for oceanographic data. Shaded ocean regions represent biological sampling areas. Source: NOAA
That El Niño delayed the onset of the annual spring upwelling of nutrient-laden water that, was nevertheless strong enough to fuel the rich West Coast ecosystem and improv environmental conditions for salmon.
NOAA Fisheries scientists presented the report to the Pacific Fishery Management Council to inform upcoming decisions on fishing seasons. The report provides a snapshot of ocean conditions, fish population abundance and habitat, and fisheries landings and fishing communities’ conditions. It gives short-term forecasts and longer term projections of how conditions across the ecosystem may evolve in 2025 and beyond.
El Niño causes the Pacific jet stream to move south and spread further east. During winter, this leads to wetter conditions than usual in the Southern U.S. and warmer and drier conditions in the North.(Source: NOAA)
Report Highlights
- Upwelling resumed even more strongly and consistently than normal, supplying a greater influx of nutrient-rich waters that improved forage conditions for many species
- Productive waters supported abundant forage speciessuch as anchovy and krill and strong production of young hake and juvenile rockfish that could contribute to commercial fisheries in future years
- Improved freshwater streamflows should support survival of juvenile salmon migrating downstream in California to the ocean
- California sea lions found enough prey amid the El Niño warming, while experiencing harmful algal blooms that led to premature birth of pups and strandings along the coast
“Each year we learn more about how this marine ecosystem functions and what we should be watching to anticipate change,” said Andrew Leising, a research oceanographer at NOAA Fisheries’ Southwest Fisheries Science Center who coauthored the new report. “We’re getting better at forecasting what is coming at us, at the same time we see some new twists.”
Progression of the 2024 marine heatwave in the northeast Pacific Ocean. Colors represent standardized SST anomalies. Heavy black lines denote regions that meet the criteria for a marine heatwave (see Appendix F.2). Gray contours represent sea level pressure (in hectoPascals) and arrows represent wind speed and direction. Source: NOAA
Forage Species Plentiful
While delayed by El Niño, annual spring upwelling along the coast provided nutrients for rapid growth of zooplankton to feed the marine food web. Studies of the diets of highly migratory predators such as swordfish and some species of tuna benefited from abundant forage species such as anchovies and hake, and myctophids.
Harmful algal blooms closed some fisheries and killed some marine mammals in Southern California. However, the strong upwelling of cold water along most of the coast helped hold a large marine heatwave offshore. Similar marine heatwaves have repeatedly formed in the Pacific over the last decade, shifting species and reducing productivity. Salmon have suffered from the warmer waters, which often reduce survival of salmon in the ocean.
Diets of albacore tuna, swordfish, and bluefin tuna sampled from commercial and recreational fisheries in the CCE, 2008 - 2023. Data are proportional contributions of four key prey classes. Source: NOAA. (Click on the image to enlarge it)
Declining salmon returns associated with warmer ocean waters forced the closures of salmon fishing in California over the last 2 years. The boom in anchovies, which contain an enzyme that breaks down thiamine, a nutrient important to the health of their many predators, has also left many salmon deficient in thiamine, or Vitamin B. The offspring of adult salmon that preyed heavily upon anchovies often cannot swim and survive, with 25 percent or more dying from malnutrition.
Colder Waters Benefit Salmon
This year, though, cooler coastal waters should improve survival of young salmon entering the ocean in California. It could also promote improved Chinook salmon returns to the Columbia River system. The report predicted positive expectations for 2025 Columbia Chinook returns and better conditions for California salmon smolts migrating down rivers to the ocean.
The report adds that catches of juvenile yearling coho salmon were above average for a second straight year. This suggests an increasing five-year trend in their early marine survival.
The weight and growth of California sea lion pups in 2023 was slightly lower than usual. The renewed upwelling in 2024 supported enough forage species for above average pup survival. However, harmful algal blooms off Southern California produced a neurotoxin called domoic acid that affected sea lions in some rookeries and haulouts. Many pups were born prematurely, and many stranded on beaches, sometimes with seizures caused by the neurotoxin.
Scientists also evaluated their predictions from last year as to how the ecosystem would change over the course of the year. For instance, they correctly predicted that the size and abundance of krill would decline with El Niño, but then quickly recover.
 Revenue from the Dungeness crab fishery in California rose, as did coastwide landings for commercial fisheries, including highly migratory species, market squid, and shrimp. The whiting (hake) fishery is the largest on the West Coast by volume; landings declined from 2023 to 2024 due to a combination of a southerly shift in the species’ distribution and a decline in fishing capacity in the whiting mothership sector. In addition to providing indicators on fisheries targeting diverse species groups, the report also assessed the engagement of coastal communities in fisheries and their socioeconomic vulnerability to large-scale challenges like severe reductions in fish stock availability to fisheries.
“We know that changes will continue to affect the California Current Ecosystem, so we want to understand what that means to the environment and the economy,” said Mary Hunsicker, coauthor of the new report. “Are the species and the economy healthy and diverse enough to provide the resilience that they need going forward?”
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