Tracy Press

With the Delta smelt population on the ropes, scientists working near Byron await a state grant that they hope will help solve the riddle of the tiny fish's decline.

Tiny adult Delta smelt rest in a net, caught from one of the Conservation and Culture Laboratory tanks. Glenn Moore/Tracy Press

Ecologists might lament the decline of the Delta smelt, but scientists at a lab next to Clifton Court Forebay, just south of Byron, expect to see an increase in the number of smelt they work with.

Since 1995, the U.C. Davis Fish Conservation and Culture Laboratory has been the state’s main breeding program for captive smelt. U.C. Davis expanded the lab in 2003, and in 2008 a $1.2 million grant from the State Water Resources Control Board and Department of Water Resources will enable the lab to expand again in an existing building.

Bradd Baskerville-Bridges, one of the lab’s directors since 1998, said the expansion comes at a critical time. As of last year, the population of wild Delta smelt declined so far that researchers are no longer allowed to take the smelt out of their native habitat.

"We had already come to the conclusion that it’s not the responsible thing to do," Baskerville-Bridges said. "Fortunately, we kept our brood stock from last year and will spawn them as 2-year-olds."

Baskerville-Bridges said about 600 fish are still alive from when researchers last collected smelt from the Delta in December 2006. Typically, a female will produce about 1,000 eggs, but some of the older fish can produce 4,000 to 5,000 eggs. They also have second-generation fish in their lab, which is separated into areas for spawning, larvae, juveniles and adult smelt.

The fish spawn in the wild between February and May, but the season is longer in the lab and more of the fish spawned will survive as compared to those in the wild. The 2008 population already includes larvae and groups of thousands of eggs ready to hatch.

Joan Lindbergh, who has been at the lab since 1995 when the whole lab was housed in a single converted shipping container, said the lab could potentially produce 100,000 to 200,000 fish every year.

Bradd Baskerville-Bridges of the U.C. Davis Fish Conservation and Cultural Lab looks at a sample of smelt eggs at the laboratories off Byron Road. Researchers are no

But the lab’s emphasis is identifying the genetic makeup and family groups of the fish, much like a pedigree. The lab expansion will enable researchers to do more detailed isolation of family groups among the fish, which will translate to better assurance of genetic diversity in future populations of fish bred in captivity.

For that reason, the number of fish produced in the lab is much lower, about 60,000 in 2006, but the lab can provide other researchers with detailed information on any particular fish used in a study.

The refuge and breeding program isn’t designed to produce fish to go back into the Delta, but it will provide fish for research into the species’ life cycles, feeding habits, habitat needs and other studies.

"If you want to do any laboratory study you have to have fish of a known origin and known age," Baskerville-Bridges said. Researchers who use the fish include other scientists at U.C. Davis, the California Department of Fish and Game, the U.S. Bureau of Reclamation and the U.S. Fish and Wildlife Service.

Researchers also used raised fish to study how screens designed to keep fish out of irrigation pumps, including the huge state and federal export pumps north of Tracy, affect the fish, and also how other factors, such as Delta water quality and predators, affect the fish’s overall numbers.

While the smelt are believed to be at their lowest numbers ever in the wild, the lab directors said that breeding fish for release back into the Delta is not practical if the conditions that caused their decline in the first place are not corrected.

"They’ve considered that, but there are real downsides to producing cultured fish and releasing them into the wild," Lindberg said. "If the cultured fish breed with the wild fish, it could bring down the health of the wild fish.

"When it gets way down to a bottleneck, that’s when people consider putting laboratory animals back into the wild."

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