Extinction's Edge: Zero Delta smelt found in September 2021 during CDFW Fall Midwater Trawl Survey

By Dan Bacher | 

For the fifth September in a row, the California Department of Fish and Wildlife has caught zero Delta smelt in its Fall Midwater Trawl Survey (FMWT) throughout the Sacramento-San Joaquin River Delta.

Once the most abundant fish on the entire estuary, the fish is now near extinction in the wild, although UC Davis continues to raise the fish in a captive breeding program.

The Delta smelt population has plummeted over the decades since the State Water Project began exporting Delta water to San Joaquin Valley grower sin 1967.

While there are several factors that scientists pinpoint for the ecosystem collapse, including toxic chemicals, decreasing water quality and invasive species, no factor figures greater in the collapse than the export of massive quantities of state and federal project water from the Delta to San Joaquin Valley agribusiness interests like the Resnicks and the Westlands Water District. 

The last year when Delta smelt were recorded in September was in 2015, when 5 were caught by the CDFW. The last year when any Delta smelt were caught during the four-month survey was in 2016, when a total of 8 Delta smelt were reported.

The Delta smelt is an indicator species that demonstrates the health of the Delta, the largest estuary on the West Coast of the Americas.

“All signs point to the Delta smelt as disappearing from the wild this year, or, perhaps, 2022,” according to a California Water Blog post by Peter Moyle, Karrigan Börk, John Durand, T-C Hung and Andrew L. Rypel on January 10, 2021. “In case you had forgotten, the Delta smelt is an attractive, translucent little fish that eats plankton, has a one-year life cycle, and smells like cucumbers.”

The CDFW also found only one longfin smelt, another native fish species, in its surveying stations throughout the Delta. The survey didn’t find any longfin smelt last September.

For the tenth September in a row, the CDFW caught zero Sacramento splittail, a native member of the minnow family. 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, fared poorly also. The CDFW caught only 1 young-of-the-year striped bass this September, compared with 11 last September.

The catch of American shad, another introduced species, did poorly this September also. The CDFW found only 24 of this member of the herring family, compared with 202 in September 2020.

Finally, the CDFW caught just 11 threadfin shad, an introduced forage fish, this September. That compares to 43 fish last September. 

I will be monitoring this survey every month and writing a brief report on the monthly results for each species. When the survey terminates in December and the final results are compiled for the four months, I will write a comprehensive report on the survey and its ecological implications.

Between 1967 and 2020, the California Department of Fish and Wildlife’s (CDFW) Fall Midwater Trawl (FMWT) abundance indices (combined September, October, November and December surveys) 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 (1967-1971 vs. 2016-2020), 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.

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