California should change fishing rules after hundreds of sturgeon die, scientists say
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A dozen independent fish scientists are calling for urgent changes to sport fishing rules to save California’s largest freshwater fish after an unprecedented red tide this summer left hundreds of them dead in the estuary on Sacramento’s doorstep.
The fish is the white sturgeon — an ancient species native to the West Coast.
The largest freshwater species in North America, they can grow 15 to 20 feet long, weigh a ton and live for nearly a century. Some of these behemoths migrate from the Pacific Ocean up the Sacramento River through California’s capital city each year.
The fish that look something like a cross between a shark and a catfish have existed more or less biologically unchanged since the time of the dinosaurs. They’ve managed to survive as modern humans polluted their habitats and built dams and levees across their migration routes.
But this summer’s deadly red tide has independent scientists worried about the future of this species. They’re calling on the state to change fishing rules to require anglers release any sturgeon they catch — a move that would likely be controversial for the state’s 46,000 sturgeon anglers.
In late August and early September, hundreds of sturgeon carcasses, as well as numerous other fish species including sharks and rays, started popping up dead in the San Francisco and San Pablo bays at the edge of the Sacramento-San Joaquin Delta.
The die offs coincided with an unusually massive outbreak of Heterosigma akashiwo, a type of algae that causes the toxic, oxygen-depleting blooms known as red tides that are deadly to fish and other aquatic life.
Andrew Rypel, a fisheries biologist and sturgeon expert at UC Davis, said the fishing changes are needed at a “critical point in time” if Californians want to keep the fish from ending up protected under the state or federal endangered species acts — decisions that would likely prohibit any fishing for them.
“We had a declining population already,” Rypel said. “Then we had this big fish kill. Hey, what are we going to do about this?”
Unclear how many fish perished
State biologists are still trying to sort through eyewitness tallies of dead fish to make an estimate of how many sturgeon died in the unusually massive red tide that spread through at least 1/3 of the sturgeon’s known summer range.
They’ve received reports of more than 670 dead sturgeon, though some of those numbers could be duplicates, Jordan Traverso, a spokeswoman for the Department of Fish and Wildlife, said in an emailed response to The Sacramento Bee’s request for an interview with a state biologist.
Whatever the official tally ends up being, it’s likely a substantial undercount since sturgeon tend to sink when they die instead of floating on the surface, Rypel said.
The huge numbers of dead fish — many of them adults — are especially troubling because the vast majority of California’s white sturgeon are believed to spend most of their time in the estuary. It takes at least 10 years before a sturgeon becomes mature enough to reproduce.
Before the fish kill, one recent study estimated that California’s white sturgeon numbers have been declining every year by as much as 5%, Rypel said.
Faced with such grim figures, Rypel and 11 other fish scientists at UC Davis, UC Santa Cruz and the private fisheries consulting firm Cramer Fish Sciences last week co-authored a blog that calls for state fisheries regulators to take immediate action to protect the sturgeon that they called “the redwoods of the San Francisco Estuary.”
“Although white sturgeon have proven resilient in the past, there is no reason to be sanguine about their future now, especially in California,” the scientists wrote.
Their top recommendation: Temporarily prohibiting anyone from keeping white sturgeon they catch in California, at least until the species recovers.
As it stands, California anglers are only allowed to keep three white sturgeon each year, and only if they’re a certain size. No one has formally petitioned the California Fish and Game Commission to change the rules, Traverso said. The commission sets sport fishing regulations and decides whether to protect species under the California Endangered Species Act.
James Stone, the president of the Nor-Cal Guides and Sportsmen’s Association, a top sport fishing advocacy group, declined to comment on the proposal to make California’s sturgeon fishery catch-and-release only.
He said the association is waiting on the state to finish its analysis on the fish kill before taking a position. Still, even before the red tide, he said anglers have been troubled by a decline in the sturgeon over the years and the lack of research on the popular sport fish.
“There isn’t enough data on white sturgeon,” Stone said. “We always could use more.”
State officials acknowledged they don’t have a good enough handle on the white sturgeon population to make an estimate of how much of the population died in the summer’s red tide.
Better sturgeon reporting needed
Anglers can help scientists on the data front, Rypel said.
California anglers are issued sturgeon reporting cards. They’re required to make a note on their cards of any sturgeon they catch, even if they’re released.
The cards are supposed to be mailed in or reported online, but only about one in three report card holders ever send in the data.
Last year, 33,008 of the 46,699 cards the state issued to anglers weren’t returned — numbers that “make it difficult to estimate the harvest rate that’s going on in the population,” Rypel said.
For now, the state has no plans to change the reporting rules or add new penalties for anglers who fail to report their catch, though state officials say they’re working on getting anglers to report more of their catches.
“We have implemented the ability to report online which improved reporting compliance,” Traverso said in an email. “And we are currently working on developing a mobile app that will ease reporting.”
Data problems aside, Rypel said the broader worry for the sturgeon is a future with more deadly red tides.
California is at the southern edge of the white sturgeon’s range, where climate change is bringing harsher droughts and more punishing heatwaves that warm up water and create perfect conditions for the algal blooms that proved so deadly for this long-lived species this summer.
“It’s worth thinking about how we respond to them,” Rypel said of the red tides, “and whether there are other things we can do to help conserve fish in the face of that.”
This story was originally published November 10, 2022 at 5:30 AM with the headline "California should change fishing rules after hundreds of sturgeon die, scientists say."