After 2022’s Fatal Algal Bloom, Scientists Fear the Bay’s Sturgeon Could Go Extinct

In an open letter, they’re calling for California to consider making white sturgeon fishing catch-and-release for now.

December 21, 2022
A white sturgeon with worn-down barbells—the whisker-like organs that dangle in front of its mouth. Sturgeon use barbells as well as external taste buds to detect morsels in the mudflats. (Photo by Andrea Shreier)
A white sturgeon with worn-down barbells—the whisker-like organs that dangle in front of its mouth. Sturgeon use barbells as well as external taste buds to detect morsels in the mudflats. (Photo by Andrea Shreier)

At Point Pinole, 21 sturgeon carcasses––some more than seven feet long––lay strewn along a mile-long stretch of beach in late August 2022, baking in the relentless heat. It was the peak of the largest harmful algal bloom on record in San Francisco Bay, and people noticed. 

Around the Bay, members of the public made hundreds of sturgeon carcass reports to government agencies and on the citizen-observation platform iNaturalist—so many that four months later, the California Department of Fish and Wildlife is still sorting through them.

Sturgeon survived the calamity that struck down the dinosaurs, the movement of continents across the ages, and the advent of the Anthropocene, hardly changing over 200 million years. But this summer’s harmful algal bloom, also known as a red tide, triggered the largest sturgeon mortality event ever recorded in the San Francisco Bay estuary.

In November, 12 fisheries scientists wrote an open letter expressing worry that this catastrophic event could push the Bay’s white sturgeon population onto a path toward extinction. The authors of the letter include fisheries and sturgeon scientists from UC Davis, UC Santa Cruz, the National Oceanic and Atmospheric Administration, and Cramer Fish Sciences, a fishery science consultancy. The letter was published on the California Water Blog, a collaborative project based at UC Davis’s Center for Watershed Sciences.

“We’re very alarmed,” says Levi Lewis, a fisheries biologist at UC Davis who cowrote the letter. “Sturgeon are long-lived, very slow-reproducing fish that cannot tolerate high levels of mortality.”

Both green and white sturgeon live in the Bay. The Bay’s green sturgeon are federally listed as threatened, and must be released if caught, while anglers can keep one white sturgeon 40 to 60 inches in length per day with an annual limit of three. White sturgeon are a California species of special concern.

According to the CDFW, at least 170 white sturgeon, 16 green sturgeon and 632 sturgeon of unidentified species perished during the bloom. Because dead sturgeon might sink and do not always wash ashore, the total number of affected fish may be much higher. 

“Action needs to be taken now to protect California white sturgeon to assure this ancient population survives long into the future,” the scientists wrote. They urged California to fund comprehensive research on population numbers, habitats, and causes of death––and make white sturgeon fishing strictly catch-and-release to help the population recover. “While monitoring is notoriously expensive, it is in the long run much cheaper than trying to recover an (Endangered Species Act)-listed species,” the letter says.

“Right now, we don’t know exactly how many sturgeons are even out there,” says UC Davis fish  geneticist and conservation biologist Andrea Schreier, another of the cowriters. “We have an idea of where in the Sacramento River they spawn, but we don’t know the exact spawning location.”

All 27 sturgeon species worldwide are considered vulnerable or in danger of extinction by the International Union for the Conservation of Nature. Sturgeon are particularly sensitive to mortality from harmful algal blooms and human activity in the San Francisco Bay because of their periodic reproduction, long migrations between the ocean or Bay and freshwater rivers, long lifespans, and slow maturation. It could take decades for the surviving sturgeon to replace the fish lost in the 2022 algal bloom.

The CDFW monitors sturgeon populations, enforces fishing regulations, and makes recommendations to the state Fish and Game Commission, which sets policy, including listing endangered species. Funding comes from several government agencies.

CDFW Fisheries Branch Chief Jay Rowan acknowledged the scientists’ concerns in an email to Bay Nature. “We have reviewed the open letter and existing data, and we do not feel that an emergency regulation change to a catch-and-release fishery only is necessary at this time,” Rowan wrote.

CDFW sturgeon manager James Hobbs also wrote that the agency is not working on a California Endangered Species Act listing or recommending a regulation change for white sturgeon.

‘If you smell something, say something’

Sturgeon are prized for their massive size, tasty meat and eggs, and epic fishing battles. Every year, anglers compete in sturgeon derbies in the Sacramento-San Joaquin River Delta to catch sturgeon of specific sizes for cash prizes. 

“They’re a hoot to catch,” says Lewis. “They’re these huge, 100-pound fish that leap into the air like marlin––and we can catch them right here in our backyard in San Francisco Bay.” 

Anglers can catch three white sturgeon per year by purchasing a CDFW “sturgeon report card.” An average of nearly 2,000 sturgeon per year have been legally harvested since 2007, according to report cards turned into the CDFW. But only about 30 percent of anglers who buy the cards turn them in.

Zack Medinas, a charter boat captain who takes people out sturgeon fishing—catch and release only, he says—loves catching the prehistoric behemoths, and has been concerned about their well-being for years. He even helps scientists find sturgeon hot spots during annual surveys, and participates in tagging efforts. Last summer, Medinas knew something was very wrong as he motored under the Golden Gate on the way back from a salmon-fishing trip. The Bay water was a dark, brownish red––“like bloody motor oil,” says Medinas. “It was horrible.”

The foreboding waters were caused by a tremendous bloom of the algae Heterosigma akashiwo. Sturgeon and other fish may have died from toxins released by H. akashiwo, or because they ran out of oxygen as the algae took over. It happened fast, and fisheries scientists were caught off guard, Lewis said; labs weren’t prepared to do the necropsies necessary to collect evidence that could help answer such questions. It’s only thanks to members of the public reporting carcasses across the coast, Bay and Delta regions that scientists have been able to more accurately assess how many fish died.

“This fish has a huge migratory range, and it’s very hard to keep track of it throughout its entire range,” says John Kelly, CDFW’s statewide sturgeon coordinator. “Citizen science makes that possible.” 

Even before the bloom, sturgeon populations in the Bay Area were threatened by pollution, caviar poaching, sea lion predation, ship strikes and habitat degradation. The California Sturgeon Project—a collaboration of the California Department of Water Resources, CDFW, UC Davis, UC Santa Cruz, Cramer Fish Sciences and NOAA Marine Fisheries Service—invites community members to report sturgeon carcasses to help scientists understand what kills them. On social media, the project urged the public, “If you smell something, say something.” As H. akashiwo bloomed across the Bay, community reports went from a trickle to multiple per day. 

Like the scientists who wrote the open letter, Medinas believes that sturgeon deserve more attention and government funding. He would like to see the state make sturgeon strictly catch-and-release for at least a couple of years to let the population recover.

“There’s a big movement of people that are really sick and tired of seeing so many of these fish killed when they’re already struggling,” says Medinas. 

Another charter captain, Steve Mitchell, of San Francisco-based Hook’d Up Sportfishing, is skeptical of the notion that sturgeon are struggling, given the lack of comprehensive population counts. 

“We know good and well that just the amount of fish that died in the red tide, that did not hurt the population of these fish,” says Mitchell. “I’ve been fishing for these fish for over 30-some years, and I have not seen anything change.”

Mitchell opposes the idea of restricting white sturgeon to catch and release. And if the population really is at risk—though he doubts this—Mitchell says a better intervention would be to ban the use of salmon roe, a nearly irresistible treat for sturgeon that anglers often use to bait them. 

Based on annual CDFW surveys done each fall in the San Pablo Bay, there were about 35,000 white sturgeon between 40 to 60 inches long in 2020. A 2019 study, coauthored by CDFW scientists, predicts sturgeon will decline by 4.6 percent a year over the next 20 years under current harvest rates.

Prolonged drought has diminished the fishes’ spawning opportunities. Female sturgeon migrate upriver every two to four years to lay their eggs, but their young need sheltered gravel beds and cool waters to hatch and survive. When the waters of spawning rivers or the Delta are too low, or water temperatures are too hot, egg-bearing females make a U-turn and head back to the Bay, waiting to lay their eggs until conditions improve. Heat waves further threaten fish by decreasing the water’s oxygen levels, and harmful algal blooms are more likely as climate change brings warmer temperatures.

“We are concerned for the status of the species and are continuing to evaluate available data,” wrote Rowan from the CDFW. “If we come to the conclusion that a regulation change is necessary, we will work closely with the angling community and through the Fish and Game Commission’s public process.”

For now, the CDFW’s Hobbs wrote, the agency continues to analyze carcass data, which involves combing through all the public reports to verify them and eliminate duplicates; this may take another month to finish.

“We’re very lucky to have white and green sturgeon in our system,” says Shreier, the fish geneticist. “Hopefully, with some additional research and possibly some regulation changes, we can maintain these populations into the future.”

About the Author

Guananí Gómez-Van Cortright started as Bay Nature’s first editorial fellow in July 2022 and is a recent graduate of the UC Santa Cruz Science Communication master’s program. She loves to cover living fossils (like sturgeon!), people working toward environmental solutions, and the tiny but mighty microbes that control the world.

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