Central Valley

Scientists breed smelt in case species becomes extinct in Delta

BYRON – Inside a makeshift collection of modified shipping containers lined up on a patch of asphalt, a system of gurgling pipes and buckets holds the Delta's future. Or, at least, one future.

These faded steel boxes house the beginnings of a new refuge population of threatened Delta smelt. The fish, only finger-length at adulthood, could be used one day to restore the population if their wild kin go extinct.

Unfortunately, extinction is all too likely after five years of steep population declines for the smelt and four other fish species in the Sacramento-San Joaquin Delta. All are known as "pelagic" fish because they live in the Delta's moving water column.

Scientists have been unable to explain the decline, much less solve it. So the refuge smelt are intended as a last-ditch effort to save the species, long considered a bellwether for the health of the estuary as a whole.

If the smelt disappear, scientists believe, other species will follow, along with a decline in water quality that could make Delta water undrinkable for the 25 million Californians who depend on it.

Smelt, in other words, are the lead car in an ecological train that's in danger of derailing.

"It's bigger than smelt," said Bradd Baskerville-Bridges, a marine biologist and co-director of the UC Davis Fish Conservation and Culture Laboratory, where the smelt are being raised. "It's affecting all the pelagic species right now, and there's no easy solution."

The lab has been breeding smelt for 15 years for research purposes, so scientists can learn more about how the fish respond to changing environmental conditions. But the new refuge population, which started breeding in December, has added new layers of rigor and importance to the operation.

The process is like a very specialized fish hatchery, but miniaturized. And it's a hands-on process.

Eggs and sperm are extracted by gently holding each tiny smelt in the fingertips and firmly squeezing the abdomen from head to tail. The female releases a nickel-sized puddle of eggs that resembles melted butter. The male excretes a droplet of clear sperm gathered up in a tiny suction device called a micropipette.

After mixing, the fertilized eggs are held in clear tubes about 3 inches in diameter hanging inside one climate-controlled shipping container. Each tube holds layers of fine, sandy sediment through which water is constantly pumped from bottom to top.

The eggs cling to the sediment with a flexible foot, not unlike a mushroom. After eight to 10 days, they hatch into tiny embryos to form a swirling cloud that, on first glance, resembles the foam in a mug of beer. Then you realize the cloud actually consists of about 5,000 baby smelt.

Eventually the embryos respond to light and rise to the surface of each tube, where they are drawn off into buckets to grow into juvenile fish, each ghostly transparent and no longer than a fingernail.

It then takes several months on a steady diet of tiny shrimplike animals – also raised at the lab – before the smelt reach adulthood.

"They're dependent on you like babies," said Sophie Wan, a laboratory assistant supervising the juvenile smelt. "To be working with a fish that's so close to being extinct is really interesting. It's important. People don't know how important it is."

The lab is creating the refuge population from a parent generation of just 500 smelt gathered from the Delta in December 2006. These are the last wild fish the lab was able to obtain before officials halted scientific collections in the Delta – another drastic step taken to protect the species.

These parents will produce about 5,000 young for the first generation of refuge fish, which must be tracked as individuals to ensure their genetic diversity is maintained when they become parents of the next generation in 2009.

That means more tubes, buckets and tanks.

State agencies recently contributed $2.1 million toward the effort to hire more people for the project and expand the facility into a nearby warehouse, expected to be ready in April.

There are currently no plans to reintroduce these fish. In fact, almost no one wants that to happen yet. At the moment, they represent only a backup plan.

Yet it's vital to ensure diversity in the refuge fish so that if they are reintroduced, they will behave like wild fish and not compromise any remaining in the wild.

So in addition to all the breeding steps, the lab now uses tiny scissors to take a fin clip from each male and female parent. These are stored in a color-coded vial for each fish – red for girls, green for boys – and shipped to researchers on the UC Davis campus for genetic analysis.

Scientists believe a variety of factors have contributed to the smelt's decline, including excessive water exports from the Delta to Southern California, water pollution, and invasive species that outcompete smelt for food.

Research using fish raised at the lab has shown that smelt feeding and movement depend on narrow salinity and water flow requirements. This is especially true when the fish are tiny juveniles, unable to control their own movement in the Delta's strong currents.

The fish essentially evolved to thrive in the natural ebb and flow of the Delta's rivers and tides, a pattern dramatically altered by the dams and pumps that now govern the estuary.

Before reintroducing refuge smelt, scientists also need to be sure the environment is ready for them. Otherwise, these fish might meet the same fate as their wild cousins, which appear unable to thrive in the altered water chemistry, temperature and runoff that exist now.

"It's because of human influences that these changes have occurred, so it's up to us to rectify it," said Joan Lindberg, an ecologist and co-director of the lab. "We haven't been the best stewards of the Delta. So there should be a lot of effort to understand that and manage it so it's more like a natural system."

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