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Building a defense against extinction

Reclamation, partner agencies continue extraordinary effort to save Delta smelt

Media Contact: Gary Pitzer 916-978-5112
For Release: Mar 12, 2024
Delta smelt loaded into tanker truck Delta smelt loaded into tanker truck

The group of low-slung, nondescript buildings in a remote corner of San Joaquin County near Tracy are hardly noticeable and are not open to the public.

Inside, scientists are cultivating a slender, silvery minnow-like fish species with the aim of staving off its extinction, and reverse the course of decline of the long-troubled Delta smelt.

Those familiar with the plight of the Sacramento-San Joaquin Delta need no introduction to the Delta smelt. Derided by some pundits as a worthless bait fish whose existence stymies water deliveries, the once-plentiful smelt’s tale is one of the estuary’s woes. Found nowhere else on the planet, its numbers have plummeted, an indication of the many changes in the Delta ecosystem that negatively affect native fishes. 

This translucent fish lives in the open water of the Sacramento-San Joaquin Delta and completes its lifecycle in about a year. They hatch, mature and reproduce within the slightly salty to freshwaters of the Delta.

Since its listing by the Endangered Species Act 30 years ago, the Delta smelt has been the focus of an intense, comprehensive plan to protect the dwindling wild population, and in recent years to kick-start its recovery. Those years have been marked with barely perceptible advances that only protect against extinction, with occasionally noteworthy occurrences such as the release of thousands of fish via boat or tanker truck.

Such was the case on a recent winter morning as some 25,000 Delta smelt made the 50-mile trip via truck from the U.C. Davis Fish Conservation and Culture Laboratory near Tracy to the chilly, murky waters of the Sacramento River at Rio Vista. It’s the third year of the Experimental Release program, with each action adding to the trove of knowledge scientists have about the best way to supplement the much-depleted wild population of the fish.

“Every year that we do this we learn more and gain perspective on where and how we want to release the fish,” said Nick Bertrand, fish biologist with Reclamation’s Bay-Delta Office.

That includes discerning the difference between releasing fish in open water by boat or from shore via tanker truck, which is regarded as quicker and more efficient way to transport a greater number of fish.    

Reclamation funds the work at the U.C. Davis laboratory, as part of its responsibility for mitigating the operation of the Central Valley Project. Programs that supplement fish “are often the wall that prevents extinction,” said Bertrand.

Cultivation and release of Delta smelt is a multi-faceted effort involving the expertise and dedication of dozens of personnel with Reclamation, the U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, California Department of Water Resources, U.S. Geological Survey, and U.C. Davis.

Bertrand said he was introduced to the Delta smelt’s dilemma in the early 2000s in Texas when it was the subject of a segment on The Daily Show spotlighting the fish’s struggles and its use as a political football within the controversial world of California water. Since then, the smelt’s fortunes have dwindled as a multitude of ecological stressors push it to the brink of extinction.

“It’s death by a thousand cuts,” said Bertrand, when describing the many different ecological challenges facing the population.

The smelt are released after spending the first 200 days of their life at the U.C. Davis laboratory. Incubating, raising and marking them for release is a precise, calculated and labor- intensive process. They are a fragile, temperamental fish, and releases are carefully orchestrated to ensure they have the best chance for survival.

Fish release programs such as the one for the Delta smelt have a lot to compete against because they are often done in heavily altered ecosystems that make fish recovery a difficult proposition, said Bertrand. He praised the agencies and U.C. Davis team for getting smelt into the culture laboratory early, successfully managing the genetics of the population and establishing a program that has the greatest chance of success. 

It’s been a long process, about 30 years, to successfully culture a genetically diverse population of Delta smelt at the U.C. Davis laboratory with “confidence and consistency,” said Tien-Chieh Hung, director at the facility. Ultimately, the aim is to aid the recovery of a fish that’s struggling to survive.

“We would like to see the population in the wild have a good recruitment by themselves without the need of the supplementation of lab-bred fish,” he said. “That would be considered a success.”

Even with the odds stacked against Delta smelt, experts believe a supplementation program can succeed. “The optimism is high,” said Katherine Sun, fish biologist with the Fish and Wildlife Service’s Bay-Delta office. “We have demonstrated that we can transport them from the facility to the wild [and] we are doing mini experiments to ensure that process isn’t too stressful.”

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