The largest freshwater fish in North America, which was once abundant in California’s major rivers and San Francisco Bay, has declined in numbers to a point that state officials will consider whether to protect the fish as a threatened species under the state’s Endangered Species Act.

White sturgeon can grow to more than 10 feet long and spend much of their lives in San Francisco Bay, swimming upstream in rivers to spawn. Some white sturgeon are thought to live as long as a century.

Recent population estimates indicate the fish have been struggling to survive in the face of multiple pressures.

The California Fish and Game Commission voted last week to accept a petition that calls for placing white sturgeon on the state’s endangered species list. The commission’s decision that protections may be warranted starts a review by state fisheries experts, who are expected to present a report within about a year. The commission will then decide whether to declare white sturgeon a threatened species.

Proponents of imposing protections say the fish are threatened by diversions of water that reduce river flows, harmful algae blooms that can trigger fish kills, and overfishing by recreational anglers. They say the fish are particularly vulnerable because they spawn infrequently — only in wet years that bring high river flows.

The giant size of white sturgeon makes them an outlier among fish species in the Sacramento-San Joaquin River Delta estuary.

“They’re even larger than a mountain lion,” Jon Rosenfield, science director for the group San Francisco Baykeeper, said in a speech to the commission. “This is an ancient lineage. White sturgeon diverged from other sturgeon and paddlefish about 46 million years ago. In that time, they’ve withstood everything that Mother Nature had to throw at them, which makes it particularly poignant that they’re having trouble surviving us.”

San Francisco Baykeeper and other groups, including California Sportfishing Protection Alliance and Restore the Delta, submitted the petition last year calling for listing the species as threatened.

If the state ultimately declares white sturgeon a threatened species, the protections could further complicate debates over water management and ecological protections in the delta, the central hub of the state’s water system, where pumps fill aqueducts that supply farms and cities across California.

Advocates for protecting the fish argue that the state’s plans for infrastructure projects such as Sites reservoir and a proposed water tunnel in the delta would further imperil the species.

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