Saving Seafood

Anglers Catch Salmon for Science as Tracking Reveals Risks Facing Adult Fall Chinook

December 2, 2025 — Many thousands of fall-run Chinook salmon migrated beneath the Golden Gate Bridge into the upper Sacramento River to spawn this fall. About 100 of the adult fish carried small tags that signaled their location as they went.

A monitoring network tracked the fish, showing their progress online in real time as part of a joint project by scientists at NOAA Fisheries and UC Santa Cruz. They followed adult salmon through the Sacramento-San Joaquin River Delta into Central Valley Rivers and their tributaries. The scientists want to know what affects salmon survival and how many fish reach their spawning grounds.

“Are the salmon burning too much energy, and what factors affect this?” asked Miles Daniels, who leads the project for NOAA Fisheries’ Southwest Fisheries Science Center. The center operates a research laboratory adjacent to UC Santa Cruz, focusing on salmon. Adult salmon need cold water; they may stop if they hit water that is too warm. Since they do not eat on the way back upriver, delays could deplete the energy they need to complete their migration and spawn.

The research is funded by California’s State Water Board to learn more about how water temperatures influence the salmon that support valuable commercial and recreational fisheries. Officials are interested in whether water can be managed to benefit fish while still supplying Central Valley farms with irrigation water. Irrigation is vital to the production of billions of dollars worth of produce and other agricultural products every year.

Fall Chinook salmon are among today’s most abundant California salmon and have long formed the backbone of West Coast salmon fisheries. However, low numbers of returning salmon have closed California ocean waters to most recreational and all commercial salmon fishing for the last 3 years.

Read the full article at NOAA Fisheries

A Lifeline for Salmon: UCSC and NOAA Join Forces to Secure a Future for California’s Most Iconic Fish

October 30, 2025 — Nearly every day for the past 20 years, scientists from UC Santa Cruz and the National Oceanic and Atmospheric Administration (NOAA) have waded into Scott Creek, a 12-mile-long burbling stream in Santa Cruz County just a few miles north of Davenport.

Dressed in waders and toting bags and buckets, these scientists navigate the stream’s chilly waters and muddy banks in search of coho salmon. Along the coast of central California, coho salmon are endangered. But the young salmon in Scott Creek may hold the key to the species’ recovery.

As the southernmost population of coho in the state, the salmon in Scott Creek are adapted to warmer and drier conditions than their more northern cousins. By studying the evolution, ecology, and genetics of this population, scientists at UCSC and NOAA hope to gain insights that could help them ensure the survival of the species throughout California.

The project at Scott Creek is one of many that UCSC and NOAA have undertaken together to prevent the extinction of California’s iconic salmon. Since joining forces 25 years ago, the federal agency and the university have become the largest and most strategic force fighting to conserve salmon in California. But with climate change, habitat loss, overfishing, invasive species, and poor water management posing an ever-greater threat to salmon survival, the salmon-saving team continues to have its work cut out for it.

Read the full article at UC Santa Cruz

A data-driven model to help avoid ecosystem collapse

June 16, 2025 — Tipping points are the death of ecosystems. So scientists watch as warning signs gradually worsen until an ecosystem reaches the point of no return, when animal populations suddenly collapse. While tipping points can sometimes be predicted, what comes next is often shrouded in mystery, stymying efforts to prevent the impending disaster or prepare for what’s to come.

A new study by a team of researchers at the University of California, Santa Cruz, and the National Oceanic and Atmospheric Administration (NOAA) introduces a method for modeling the murky future beyond a tipping point. The paper, published on June 13 in PNAS, demonstrates how this model can act as a “crystal ball” into the future of ecosystems—providing enough lead time to intervene before there’s nothing left to save.

“It gives us this fundamental insight into predicting what’s going to happen in the future,” said Eric Palkovacs, a senior author on the paper and professor of ecology and evolutionary biology at UC Santa Cruz. “That allows us to either do the things necessary to avoid that transition, or if we’re going to experience it, to plan for it and figure out the best ways to cope with it.”

Seeing the future

In healthy ecosystems, species populations fluctuate in predictable ways: Sea urchins feed on a kelp forest, otters then feed on the urchins, and the kelp regrows. But if the ecosystem loses equilibrium, disaster can suddenly strike. If warming waters drive sea urchins to kill off a kelp forest, the ecosystem suddenly crosses a tipping point that can doom all the species it supports. The result is a new regime of population fluctuations that can be hard to correct.

“You have many of these cases where the system can live in different states. You have a state with lots of kelp, and a state without kelp,” said Lucas Medeiros, the study’s lead author and a former postdoctoral scholar at UC Santa Cruz.

Currently, researchers have some methods for predicting what lies beyond an ecosystem’s tipping point, but each approach has its tradeoffs. Some existing methods make predictions using machine-learning algorithms. However, these approaches require large datasets, which often don’t exist for research on ecosystems, where data might be collected yearly or even less frequently.

Read the full article at UC Santa Cruz

New study paints gloomy picture of climate change’s impact on commercial fishing

April 22, 2025 — A new study of some of California’s most commercially significant aquatic species paints a grim picture for the future of the state’s fishing industry under the growing threat of climate change.

The study, compiled by a host of researchers including federal and state scientists as well as researchers from UC Santa Cruz and UC Davis, looked at 34 aquatic species in an attempt to gauge how each would fare under predicted climate change scenarios.

Among the species studied were Dungeness crab, red abalone, Pacific herring, Pismo clams, pink shrimp, Pacific bonito and California spiny lobster. The group ranked each by their level of vulnerability to changing environmental conditions.

“The most striking thing that we found is that among the species that were ranked as the most highly vulnerable happened to also be some of California’s economically valuable and culturally important species,” said Mikaela Provost, assistant professor of fisheries ecology at UC Davis and co-author of the study.

California’s oceans are highly productive due to seasonal upwelling which keeps water temperatures cool and filled with nutrients. But models of future conditions forecast disruption through rising temperatures, deoxygenation and potential changes in circulation.

Read the full story at NBC Bay Area

Foraging seals enable scientists to measure fish abundance across the vast Pacific Ocean

February 14, 2025 — Over the past 60 years, marine biologists at UC Santa Cruz have monitored the behavior of northern elephant seals that journey to nearby Año Nuevo Natural Reserve. With the seals gathering on the beach by the thousands to breed and molt, generations of researchers have been able to amass more than 350,000 observations on over 50,000 seals.

With the help of powerful technologies and the intrepidness to get close enough to carefully tag, weigh, and observe these loud and lumbering marine mammals, the long-term research project has extensive historical and real-time data on their fitness, foraging success, at-sea behavior, and population dynamics.

Roxanne Beltran is next in line to lead the project, and her new study being published as the February 14 cover story for Science reports that seals can essentially act as “smart sensors” for monitoring fish populations in the ocean’s eerily dim “twilight zone.” This is the layer of water between 200 and 1,000 meters below sea level, where sunlight penetration all but stops, and today’s ocean monitoring tools cannot reach with ease. Ships and floating buoys only allow measurements of a tiny fraction of the ocean, while satellites can’t measure below the surface where fish occur.

Importantly, this zone holds the majority of the planet’s fish biomass. Because this is also where the seals feed, seals whose foraging success is tracked can provide a previously impossible way to measure the availability of fish populations across a vast ocean. This, Beltran said, represents a significant discovery because humans are considering harvesting these fish populations to satisfy humanity’s ever-increasing need for protein-rich foods.

Read the full article at UC Santa Cruz

Ecological Forecasts Offer New Insight into Changing Conditions that Can Shift Fisheries, Drive Conflicts

December 6, 2023 — Weather forecasts only look out a few days to weeks. Two new research studies describe the increasing accuracy of specialized scientific models in forecasting changes in the ocean up to a year in advance.

The models have increasing value as climate change drives shifts in ocean temperatures and other conditions with new and unexpected outcomes. The changes can have ecological and economic repercussions. For example, warming ocean temperatures increase the overlap between fishing fleets and protected species like whales and sea turtles, which can trigger fishing closures. The research was conducted by scientists at NOAA Fisheries and University of California, Santa Cruz.

NOAA Fisheries is also pursuing development of “Climate-Ready Fisheries” that adjust to changing conditions, even over the course of a single fishing season. Some forecasts examined in the new studies could provide insight as much as a year in advance. This could highlight potential conflicts or opportunities in time for managers and fishermen to do something about them. This kind of proactive management was highlighted in the recent National Climate Assessment as an important approach to addressing the impacts of climate change.

“We can now look months or even a year out and ask, what is that part of the ocean going to look like, and what does that mean for the species and for the people and industries who use it?” said Stephanie Brodie, lead author of one of the new studies. “For fisheries, it gives managers a chance to evaluate the trade-offs in reducing human-wildlife conflict and supporting an economically viable fishery.”

Read the full story at NOAA Fisheries

Survivor salmon that withstand drought and ocean warming provide a lifeline for California Chinook

November 2, 2021 — In drought years and when marine heat waves warm the Pacific Ocean, late-migrating juvenile spring-run Chinook salmon of California’s Central Valley are the ultimate survivors. They are among the few salmon that survive in those difficult years and return to spawning rivers to keep their populations alive, according to a study published October 28 in Nature Climate Change.

The trouble is that this late-migrating behavior hangs on only in a few rivers where remain cool enough for the fish to survive the summer. Today, this habitat is primarily found above barrier dams. Those fish that spend a year in their home streams as juveniles leave in the fall. They arrive in the larger and more likely to survive their one to three years at sea.

Researchers led by first author Flora Cordoleani, associate project scientist with the Institute of Marine Sciences at UC Santa Cruz and NOAA Fisheries, based their findings on an analysis of the ear bones of , called otoliths. These bones incorporate the distinctive isotope ratios of different Central Valley Rivers and the ocean as they grow sequential layers.

Read the full story at PHYS.org

 

Fish in California estuaries are evolving as climate change alters their habitat

November 21, 2019 — The threespine stickleback, a small fish found throughout the coastal areas of the Northern Hemisphere, is famously variable in appearance from one location to another, making it an ideal subject for studying how species adapt to different environments. A new study shows that stickleback populations in estuaries along the coast of California have evolved over the past 40 years as climate change has altered their coastal habitats.

The study, published November 21 in Global Change Biology, looked at variation in the armoring that protects the  from predators, specifically the number of bony plates along their sides (called lateral plates). Previous research showed that populations in northern California have a more complete set of this armoring than populations in southern California, corresponding to differences in their habitats.

“There’s a gradient from drier systems in the south, where the estuaries are more pond-like, with more vegetation, to increasingly more open, river-like systems as you go north,” explained coauthor Eric Palkovacs, associate professor of ecology and evolutionary biology at UC Santa Cruz.

The new study found that threespine stickleback in some California estuaries are evolving to have fewer lateral plates as their habitats become more pond-like due to a warmer, drier climate. Stickleback populations at some central California sites are now looking more like the low-plated populations typical of southern California.

Read the full story at PHYS.org

Review of noise impacts on marine mammals yields new policy recommendations

March 13, 2019 — Marine mammals are particularly sensitive to noise pollution because they rely on sound for so many essential functions, including communication, navigation, finding food, and avoiding predators. An expert panel has now published a comprehensive assessment of the available science on how noise exposure affects hearing in marine mammals, providing scientific recommendations for noise exposure criteria that could have far-reaching regulatory implications.

Published March 12 in Aquatic Mammals, the paper is a major revision of the first such assessment, published in 2007 in the same journal. Both efforts were led by Brandon Southall, a research associate at the Institute of Marine Sciences at UC Santa Cruz and senior scientist at Southall Environmental Associates.

“One of the things we did in 2007 was to identify major gaps in our knowledge, and we now have considerably more data. We thought there was enough new science to reconvene the panel and revisit these issues,” said Southall, who served as director of NOAA’s Ocean Acoustics Program from 2004 to 2009.

Read the full story at UC Santa Cruz Newscenter