DAVIS, Calif. — Last summer, state fish and game workers dragged a net dozens of times through the milk-chocolate waters of the Sacramento-San Joaquin Delta, looking for a tiny, steely blue fish found nowhere else in the world. The catch, 17 delta smelt, was shockingly small.
Never in the nearly five decades that the state has monitored smelt in the sprawling delta, where two of the state's biggest rivers converge just east of San Francisco Bay, have their numbers been as dismal. So abundant a generation ago that fishermen used the translucent, finger-length fish for bait, the delta smelt population has plummeted from the millions to an estimated 100,000 or less -- bringing it, some warn, to the brink of extinction.
The smelt's recent collapse, coupled with the decline of three other fish species that swim in the delta, has launched a multimillion-dollar scientific detective hunt for the reason.
There is a sense of urgency because the smelt's only home is one of California's most important, if troubled, ecosystems. The hub of the state's giant water system and a Bay Area playground, the delta is a vital link in the estuary chain that supports most of California's commercial fish species.
If the smelt is lost, it will be one more sign that the delta is too taxed to give Californians everything they demand of it.
"The only way we'll be able to save this estuary and the valuable resources it provides ... is by figuring out what's going wrong for this little fish," said Tina Swanson, a senior scientist with the Bay Institute, which last month petitioned the federal government to upgrade the smelt's protected status to endangered.
Environmental safeguards in place for more than a decade have altered the operation of the big government water projects, sometimes even shutting down the enormous delta pumps that supply two out of three Californians. But that hasn't been enough.
"I think for delta smelt it's looking pretty gloomy," said UC Davis research ecologist Bill Bennett, who has spent much of the last decade studying the fish's decline. The delta "is really not a good place for them to live anymore. It's a very different aquarium these fish are in than it was 30 years ago."
