Zero Delta was smelt in the CDFW trawl survey for the fifth consecutive October

Once the most abundant fish in the entire estuary, Delta smelt are now extinct in the wild, although UC Davis continues to breed the fish in a captive breeding program. In an experiment late last year and early this year, thousands of these hatchery-raised smelt were released into the Delta.

On December 14 and 15, 2022, the US Fish and Wildlife Service and CDFW, along with the California Department of Water Resources and the US Bureau of Reclamation, experimentally released 12,800 hatchery-raised Delta smelt into the Delta for the first time. The agencies released another shipment in January and three more in early February.

The purpose of this Delta smelt project is to “benefit species conservation through experimental release studies into a portion of the current range of captive-produced fish,” according to the service:

The Delta smelt population has declined dramatically in the decades since the State Water Project began exporting Delta water to San Joaquin Valley growers in 1967.

While there are several factors that scientists have identified for the ecosystem’s collapse, including toxic chemicals, declining water quality, and invasive species, none is a bigger factor in the collapse than the diversion of water from Central Valley rivers and the export of large amounts of state and federal project water. From the Delta to the San Joaquin Valley, agribusiness interests such as Stewart and Lynda Resnick, owners of the Wonderful Company and Westlands Water District.

“Delta Smelt is the thread that connects the Delta to the river system,” said Winnemem Wintu Chief Caleen Sisk. “We all need to understand how this affects all water systems in the state. They are the indispensable thread that holds the Delta system together with Chinook salmon.”

The department also announced its index 261 Longfin smelt, a cousin of the Delta smelt, at gauging stations throughout the Delta this October. This compared to just 12 in October last year. This is the largest index reported for any October since 1999 2736 information was provided.

The US Fish and Wildlife Service proposed on October 6 that a distinct population segment of the San Francisco Bay-Delta be listed as a “threatened” species under the Endangered Species Act (ESA).

“Scientific analyzes indicate that the Bay-Delta longfin smelt is threatened with extinction throughout its range,” the service said in a statement. The Service is now seeking public comment within 60 days of publication of the proposed rule in the Federal Register.

In response to the proposed listing, Jon Rosenfield, chief scientist at San Francisco Baykeeper and a noted expert on longfin smelt ecology, said, “Our local longfin smelt population is particularly sensitive to changes in the volume of inflowing freshwater. to San Francisco Bay. The catastrophic decline in longfin smelt is another sign that the flow of water from the rivers feeding the bay is unsustainable.

Eel smelt were once one of the most abundant fish in San Francisco Bay, which spans the Sacramento-San Joaquin River delta, Rosenfield said.

“However, annual state surveys show that longline smelt in San Francisco Bay have been at or near record lows nearly every year since 2007 — and the species is virtually undetectable in other Northern California estuaries,” Rosenfield said.

For the eighteenth consecutive October, state scientists caught zero Sacramento splittails, a native member of the minnow family found only in the Delta Estuary and Central Valley rivers. The last time any split was reported in the October survey was in 2004 2 splittail werer reported.

Eastern Seaboard striped bass, imported to the Delta for 130 years, continue to fare poorly, but this October’s index was better than last year. Caught the CDFW index 34 young of the year striped bass this October compared to 10 last October.

Although the index is down sharply from historical levels, another introduced species, American shad, was better than last September. Biologists reported an index of 155 this October, compared to 53 in October 2021 for this member of the herring family.

Finally, CDFW officials reported an index of 39 threadfin shad, a forage fish introduced in October 2022. This is up from the 28 index reported last October.

Since the State Water Project was launched in 1967, the decline of the Delta’s pelagic species has been catastrophic. Between 1967 and 2020, the state’s Fall Midwater Trawl abundance indices for striped bass, Delta smelt, longfin smelt, American shad, splittail and threadfinsmelt were 99.7, according to Bill Jennings, executive director of the California Sport Fisheries Conservation Alliance (CSPA). , decreased by 100, 99.96, 67.9, 100 and 95 percent.

Taking the five-year average, declines for striped bass, Delta smelt, longfin smelt, American shad, splittail, and threadfin shad were 98.1, 99.8, 99.8, 26.2, 99.3, and 94.3 percent, respectively. does. Jennings said.

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