Zero Delta smelt found in Midwater Trawl Survey for seventh September in a row
For the seventh September in a row, the California Department of Fish and Wildlife (CDFW) has caught zero Delta smelt during its Fall Midwater Trawl Survey of the Sacramento-San Joaquin River Delta.
The last September when Delta smelt, an indicator species that demonstrates the relative health of the San Francisco Bay-Delta Estuary, were found in the survey was in 2015, when 5 were caught by CDFW biologists.
The last year when any Delta smelt were caught during the entire four-month survey was in 2016, when a total of 8 Delta smelt were reported.
The final results of the four month survey of pelagic (open water) fish species, from September through mid-December, won’t be available from the CDFW until late December or early January. Normally a report from the Department summarizing the results of the abundance indices (a relative measure of abundance) for the different fish species is released at that time.
The September 2022 data is available here on the annual state surveys webpage.
Once the most abundant fish on the entire estuary, the Delta smelt is now near-extinction in the wild, although U.C. Davis continues to raise the fish in a captive breeding program. Thousands of these hatchery-raised smelt were released into the Delta in an experiment late last year and early this year.
On December 14 and 15, 2022, the U.S. Fish and Wildlife Service and CDFW, along with the California Department of Water Resources and U.S. Bureau of Reclamation, experimentally released 12,800 hatchery-raised Delta smelt into the Delta for the first time. The agencies released another load of smelt in January and three more in early February.
The purpose of this Delta smelt project is to “benefit conservation of the species through studies of experimental release of captively-produced fish into a portion of its current range,” according to the service: http://ow.ly/W2Fj50HeENQ
The Delta smelt population has plummeted over 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 pinpoint for the ecosystem collapse, including toxic chemicals, decreasing water quality and invasive species, no factors figure greater in the collapse than water diversions from Central Valley rivers and the export of massive quantities of state and federal project water from the Delta to San Joaquin Valley agribusiness interests like Stewart and Lynda Resnick, owners of the Wonderful Company, and the Westlands Water District.
”Delta Smelt are the thread that ties the Delta together with the river system,” said Caleen Sisk, Chief of the Winnemem Wintu Tribe. “We all should understand how that affects all the water systems in the state. They are the irreplaceable thread that holds the Delta system together with Chinook salmon.”
The Department also found 7 longfin smelt, a cousin of the Delta smelt, in its surveying stations throughout the Delta this September. That compares to just 1 last September.
The U.S. Fish and Wildlife Service on October 6 proposed the listing of the San Francisco Bay-Delta distinct population segment of longfin smelt as an “endangered” species under the Endangered Species Act (ESA).
”Scientific analysis shows the Bay-Delta longfin smelt is in danger of extinction throughout its range,” the service said in a statement. The Service is now seeking public comment for 60 days after publication on the proposed rule in the Federal Register.
In response to the proposed listing, Jon Rosenfield, Ph.D., senior scientist for San Francisco Baykeeper and a recognized expert on longfin smelt ecology, said, “Our local longfin smelt population is particularly sensitive to changes in the volume of fresh water flowing into San Francisco Bay. The longfin smelt’s catastrophic decline is yet another sign that water diversions from the rivers that feed the bay are unsustainable.”
Rosenfield said longfin smelt were once one of the most abundant fishes in the San Francisco Bay estuary, which includes the Sacramento-San Joaquin River Delta.
“But annual state surveys reveal that longfin smelt in San Francisco Bay have been at or near record low abundance almost every year since 2007 — and the species is nearly undetectable in other Northern California estuaries,” according to Rosenfield.
For the eleventh September in a row, state scientists also caught zero Sacramento splittail, a native member of the minnow family found only in the Delta Estuary and Central Valley rivers. The last time that any splittail were reported in the survey was in 2017, when 1 splittail was reported in December.
Striped bass, a gamefish from the Eastern Seaboard introduced to the Delta over 130 years, continue to fare very poorly, but the index was better than last year. Fire and Wildlife caught an index of 10 young-of-the-year striped bass this September, compared with 1 last September.
The American shad, another introduced species, did better than last September, although the index has declined precipitously from historical levels . Biologists reported an index of 110 for this herring family member this September, compared with 24 in September 2021.
Finally, CDFW officials reported an index of 7 threadfin shad, an introduced forage fish, in September 2022. That is lower than even the index of 11 found last September.
The decline of the Delta’s pelagi species has been catastrophic since the State Water Project went into operation in 1967. Between 1967 and 2020, the state’s Fall Midwater Trawl abundance indices for striped bass, Delta smelt, longfin smelt, American shad, splittail and threadfin shad have declined by 99.7, 100, 99.96, 67.9, 100, and 95 percent, respectively, according to Bill Jennings, Executive Director of the California Sportfishing Protection Alliance (CSPA).
“Taken as five-year averages, the declines for striped bass, Delta smelt, longfin smelt, American shad, splittail and threadfin shad are 98.1, 99.8, 99.8, 26.2, 99.3 and 94.3 percent, respectively,” said Jennings.
