November 30, 2022

By Dan Bacher

For the seventh straight September, the California Department of Fish and Wildlife caught zero Delta eel during its Fall Midwater Trawl Survey of the Sacramento-San Joaquin River Delta.

The latest Delta Meling — an indicator species for the wider ecological health estuary — was found in the September 2015 CDFW survey. Only 5 were caught by state biologists at the time.

After that, the only year Delta smelt was caught during the entire four-month study was in 2016, when a total of 8 smelt were reported.

The final results of Fish and Wildlife’s four-month survey of pelagic (open water) fish species, conducted from September to mid-December, will not be available until early next year. Current September 2022 data is available here on the Annual State Surveys webpage.

Is smelt lost in the rivers?

The Delta smoked.

Once the most common fish in the entire estuary, the Delta eel is now nearly extinct in the wild, although UC Davis continues to breed the fish in a captive breeding program. Thousands of these hatchery-grown smelt were released in an experiment in the Delta late last year and early this year.

That effort began in mid-December 2021. The U.S. Fish and Wildlife Service and CDFW, in coordination with other state and federal agencies, have experimentally released 12,800 hatchery-grown smelt in the Delta for the first time. The agencies released another shipment of smelt in January, and three more in early February.

The goal of the project is to “take advantage of the conservation of the species through studies of experimental release of captive-produced fish,” officials said.

Since the State Water Project began exporting large amounts of freshwater from Delta to growers in the San Joaquin Valley in 1967, the Delta smelt population has declined sharply in recent decades.

While there are several factors scientists point to for the collapse of the ecosystem, including toxic chemicals, declining water quality and invasive species, no factors play a greater role in the disaster than water diversions from the Delta and its rivers and tributaries. The State Water Project sends that water to operations in Central California, including the Westlands Water District and multi-billion dollar agribusinesses like the Wonderful Company, owned by Stewart and Lynda Resnick.

“Delta smelt is the thread connecting the delta to the river system,” said Caleen Sisk, chief of the Winnemem Wintu tribe. “We all need to understand how that affects all the water systems in the state. They are the irreplaceable thread that holds the Delta system together with the Chinook salmon.”

In its recent findings, CDFW also reported an index of 7 longfin melt, a cousin of the Delta melt, found in monitoring stations across the Delta in September. That compares to just 1 longfin melt last September.

The U.S. Fish and Wildlife Service proposed on Oct. 6 that the separate population segment of the San Francisco Bay-Delta longfin melt be listed as an “endangered” species under the Endangered Species Act, or ESA.

“Scientific analysis shows that the Bay-Delta longfin melt is at risk of extinction throughout its range,” the agency said in a statement. The agency is now seeking public comment for 60 days after publishing about the proposed rule in the federal registry.

Commenting on the proposed list, Jon Rosenfield, Ph.D., senior scientist for San Francisco Baykeeper and a recognized expert on longfin melt ecology, said: “Our local longfin melt population is particularly sensitive to changes in freshwater volume. The catastrophic decline of the longfin smelt is yet another sign that water diversions from the rivers that feed the bay are unsustainable.”

Rosenfield added that the longfin smelt was once one of the most common fish in the San Francisco Bay estuary, which includes the Delta.

“But annual state surveys show that longfin smelter in San Francisco Bay has hit record highs nearly every year since 2007 — and the species is nearly undetectable in other Northern California estuaries,” Rosenfield noted.

An ecosystem on the edge

The South Mokelumne River in the Delta. Photo by Scott Thomas Anderson

Adding concern is that, for the 11th September in a row, state scientists have not caught a Sacramento splittail, a native member of the minnow family found only in the Delta and Central Valley rivers. The last time a split tail was reported in the investigation was in 2017, when 1 split tail was found in December.

Striped bass, an East Coast game fish introduced to the Delta over 130 years, continues to do very poorly, but the index was better than last year. The CDFW caught an index of 10 juvenile striped bass in September, compared to 1 in September.

The American shad, another introduced species, outperformed last September, although the index has fallen sharply from historical levels. Biologists reported an index of 110 for this herring relative in September, compared to 24 in September.

Finally, in September 2022, CDFW officials reported an index of 7 threadfin shad, an introduced forage fish. That is even lower than the index of 11 reported in September last year.

The decline of the Delta’s various pelagic species began years before several California governors began supporting a proposed tunnel to export even more freshwater from the Delta. The State Department of Water Resources is still trying to get that tunnel approved.

Between 1967 and 2020, the state’s Fall Midwater Trawl’s abundance indices for striped bass, deltoid smelt, longfin smelt, American shad, split tail, and wirefin shad fell by 99.7, 100, 99.96, 67.9, 100, respectively. and 95%, according to Bill Jennings, executive director of the California Sportfishing Protection Alliance.

As a five-year average, the declines for striped bass, Delta melt, longfin melt, American shad, splittail, and threadfin shad are 98.1, 99.8, 99.8, 26.2, 99.3, and 94, respectively. 3%, Jennings added.

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