C-WIN: On the Brink: Repeat of Massive Sturgeon Die-Offs Likely

Huge die-offs of white sturgeon in the San Francisco Bay/Sacramento-San Joaquin Delta estuary over the last two years were so devastating that the California Fish and Game Commission recently moved to list the iconic gamefish under the state Endangered Species Act.

But that decision is hardly an adequate substitute for meaningful action, said Tom Cannon, a fisheries expert and consulting biologist for the California Water Impact Network. The reasons adult white sturgeon died by the thousands in 2022 and 2023 were warm water and algae blooms, conditions caused by excessive state and federal water diversions for corporate San Joaquin agriculture.

“The one meaningful thing the Newsom administration could do to avoid another kill is increase cool water flows down the Delta,” said Cannon. “But they aren’t doing that, and now we’re seeing the same conditions in the Bay/Delta that we saw in 2022 and 2023 just prior to the die-offs.”

Cannon explained summer kills of sturgeon typically happen following the June super moon cycle – commonly known as the Strawberry Moon.

“We get these extremely strong tides that quickly pull warm and nutrient-rich water from the Delta into the bay,” said Cannon. “That water then sloshes around the bay for extended periods, causing massive algae blooms. When the algae die it depletes oxygen in the water, killing sturgeon and other fish. That’s what happened in 2022 and 2023 – and that’s what’s starting to happen now.”

Cannon is charting water temperatures in the Sacramento River, the Delta, and the Bay, and his findings alarm him.

“The Sacramento River and Delta have been steadily warming since early June due to state and federal project diversions,” Cannon said, “and following the Strawberry Moon, the top two feet of the Delta’s water – the hottest layer – sluiced quickly into the Bay. Water temperatures in the bay recently hit 72 degrees F – even higher than when the sturgeon started dying last year. So we’ve set ourselves up for another catastrophe.”

Cannon noted there is a bitter irony in the current situation, given the Fish & Game Commission’s decision to list the sturgeon.

“They cited their reasons for listing, but they put too much emphasis on overfishing, which is hardly the primary issue,” said Cannon. “The Fish & Game Commission, the California Department of Fish and Wildlife, the California Department of Water Resources, the State Water Resources Control Board, Governor Newsom – they all know how to solve this problem, and that’s with less water for export almonds and other luxury crops, and more water for fish. But they won’t act.”

Cannon’s recommendations for ending the threat to white sturgeon include:

• Maintaining an average water temperature of 68 degrees F in the Lower Sacramento River at the Wilkins Slough gage. This will require raising river flow releases from the current 4,000 to 5,000 cubic-feet-a-second (cfs) to 6,000 to 8,000 cfs.

• Reducing water diversions or increasing Delta inflows as necessary during heat waves to maintain an average 68-degree temperature at the Freeport gage below the City of Sacramento.

• Implementing water diversion operational changes at the false River weir, Delta Cross-Channel gates, and the Montezuma Slough gates to reduce impacts to native fish, including sturgeon.