Sturgeon have been around far longer than humans—a jaw-dropping 200 million years to our comparatively short 6 million—and survived the cataclysm that terminated the age of dinosaurs. But can these ancient fish survive the age of people?
New insights into the secret lives of these little-known fish, as well as into their increasing vulnerability, suggest ways of strengthening protections for sturgeon in California.
All 27 remaining species of sturgeon live in the northern hemisphere and all are at risk. Threats include overfishing, poaching for their caviar, and dams that block access to their spawning grounds. Fish in the San Francisco Bay are also threatened by harmful algal blooms called red tides, which release toxins that can kill aquatic life.
The Sacramento-San Joaquin Delta is home to two sturgeon species: green and white. Green sturgeon have not been legally fished in the state since 2006, when they were federally listed as threatened. White sturgeon, a state Species of Special Concern, are fished only for sport.
At a May 16, 2023 public meeting, the California Department of Fish and Wildlife (CDFW) announced its intention to establish new regulations for the white sturgeon recreational fishery by 2025.
“The population cannot continue to support our current harvest rate,” said CDFW program manager Jonathan Nelson.
WHITE STURGEON PROTECTIONS
The agency’s goal is to keep white sturgeon from joining their green cousins on the endangered and threatened species list. Colossal and long-lived, white sturgeon historically exceeded lengths of 20 feet, weights of 1,800 pounds, and ages of a century. California’s commercial catch peaked in 1887, with a haul of more than 1.5 million pounds. Soon after, the population began to decline precipitously. In 1917, the white sturgeon commercial fishery was closed for good.
By 1954, California’s white sturgeon had recovered enough that the state established a recreational fishery. But now their numbers are shrinking again. CDFW surveys aren’t comprehensive enough to tell how big—or, in this case, how small—the white sturgeon population is.
The surveys can, however, show trends. White sturgeon abundance has dropped about two-thirds since the early 2000s. Survey data also suggest that harvest rates are too high, at about 8 percent per year versus the annual 4 percent cap that Oregon and Washington state have found sturgeon populations able to withstand.
White sturgeon also face new threats linked to climate change. Among the most disturbing is last summer’s toxic red tide in the San Francisco Bay. Adult white sturgeon spend most of their lives in the brackish waters of the Bay-Delta, leaving only to spawn in the freshwater of the Sacramento River.
High temperatures and low flows through the Bay-Delta can trigger red tides, and this one coincided with an intense August heatwave that struck when rivers were down after three years of drought. Massive fish deaths resulted and at least 864 sturgeon carcasses were identified.
“It was the largest fish kill ever recorded in the San Francisco Bay,” said CDFW sturgeon coordinator John Kelly, adding that sturgeon fatalities were almost certainly undercounted. “Sturgeon carcasses don’t float very long if at all—many of them just plain sink so there was likely more significant mortality.”
Now CDFW will evaluate options for the white sturgeon sport fishery going forward. Possibilities include a quota to keep harvest rates sustainable as well as switching to catch and release. The latter, which is required in Idaho, may also be instituted in the short term in California.
“We may need interim catch and release regulations so we don’t keep overharvesting until the new regulations are in effect,” CDFW’s Nelson noted.
WATER FOR FISH
Chris Shutes began fishing for sturgeon in the 1970s but gave it up voluntarily. He still misses it. “I’d like to go back to when you didn’t have to feel bad about catching them,” says Shutes, who grew up in Palo Alto and now directs the California Sportfishing Protection Alliance (CSPA). “But if white sturgeon get listed under the Endangered Species Act you won’t be able to fish them at all—I hope people are really thinking before they take these fish home.”
Shutes favors catch and release to give white sturgeon a chance to recover. That said, he also says the onus for sturgeon restoration does not rest solely on sport fishers. “We shouldn’t be in this situation at all,” he says, adding that all native fish have declined in the Bay-Delta. He favors maintaining more water in rivers for fish.
“We need to do a better job,” Shutes continues. “It costs water and it costs money and it’s hard—but that’s what needs to be done.”
GREEN STURGEON MIGRATION FLOWS
California already releases pulses of water from dams when it’s time for adult salmon to swim from the ocean to the rivers where they spawn. UC Davis fish researcher Andrew Rypel thinks green sturgeon, which are similarly imperiled, could also benefit from migration flows. But while the salmon life cycle is well-known, much of the sturgeon life cycle is a mystery.
“There’s a lot we still don’t know, like how they reproduce and what their migrations look like,” Rypel says.
A 2022 study he co-authored helps shed light on the hidden lives of green sturgeon. Like salmon, green sturgeon live mostly in the ocean and return to freshwater to spawn. Unlike salmon, green sturgeon return to the ocean after spawning and can live as long as people.
To learn more about green sturgeon migrations, Rypel and his colleagues analyzed 12 years of data tracking tagged adults in the Sacramento River, which is where they spawn. The researchers discovered that while these sturgeon arrive in the river in one big group in the spring, they divide into two groups after spawning.
“One batch scoots right back out to the ocean,” Rypel says. “Another batch over summers in the river and leaves in the fall after the rains begin.”
During drought years, low water levels can trap adult green sturgeon in the Sacramento River. Rypel envisions migration pulse flows in the spring and fall to help keep these fish from being stranded so they make it back to the ocean.
“There’s been a lot of interest in managing green sturgeon better since they were listed as threatened,” Rypel says. “But there’s also tension between salmon and sturgeon management.”
For example, winter-run chinook, which are federally listed as endangered, benefit from cold water releases from Lake Shasta. Winter-run chinook spawn in the upper Sacramento River from May to June, and their eggs die unless the water is below 54⁰F. But, Rypel says, cool water is “probably not great” for green sturgeon. “Cold flows from Shasta for winter-run salmon might be too cold for green sturgeon in early life-stages.”
There may be much more to sturgeon than we know. While studying green sturgeon migration, Rypel and his colleagues noticed something surprising. Small groups of these fish, perhaps six to eight, always traveled together. These groups stayed with each other while migrating up and down the river, and also returned to spawn together over multiple years. “We called them fish friends,” Rypel says. He likens sturgeon to elephants, similarly long-lived animals with strong bonds.
“We can’t forget these guys—they’re wonderful,” CSPA’s Shutes says. “There’s still a chance for sturgeon to be plentiful and rebound.”