Twenty of 31 species of prized fish are in sharp decline, including the Sacramento River winter run of Chinook salmon, coastal Coho salmon and the Sierra Nevada golden trout, the San Francisco Chronicle reported.

"Our fish need cold, clean water to survive, but they're getting less and less of it," said University of California, Davis, conservation biology professor Peter Moyle, the state's leading salmon expert.

"Dams block access. Climate change is now looming to exacerbate the threat, and it increases the urgency. All of these things are pushing our fish toward extinction," he said.

"If we allow these fish to go extinct, we've allowed the deterioration of the streams and rivers," Moyle said, noting the same waterways also supply clean drinking water to people.

One species, the bull trout, already has disappeared. The fish was last seen in the McCloud River, a Sacramento River tributary, in the 1970s, and scientists link its disappearance to the concrete Shasta Dam on the Sacramento River above Redding, Calif., and the McCloud Reservoir dam, the Chronicle reported.

The California Trout fish advocacy group, which commissioned the study, said it would use the results to try to persuade legislators and Gov. Arnold Schwarzenegger to direct the state Department of Fish and Game to provide adequate freshwater and habitats.