Five Delta fish species continue marching toward extinction, according to new data released Wednesday, a result that some observers warn may signify a major ecological shift in the West Coast's largest estuary.
The data come from an annual fall survey for fish that live in the Sacramento-San Joaquin Delta, the 740,000- acre estuary that also is the primary diversion point for drinking water enjoyed by 25 million Californians.
For four months each fall since 1967, California Fish and Game officials have used trawl nets in an effort to estimate the Delta's fish population. The product of that survey for 2007, released Wednesday, shows record-low numbers for three species: longfin smelt, Sacramento splittail and American shad. Two others, Delta smelt and striped bass, posted near-record lows.
The shad and bass are not native, but are important to the economy as sportfish.
The Delta smelt is listed as threatened under state and federal endangered species laws. Environmental groups last year submitted formal petitions to list the longfin smelt.
"These species are on the verge of extinction, and they should not be allowed to go extinct," said Peter Moyle, a University of California, Davis, professor and one of America's leading fish biologists. "It's an ecological change that is knocking out a precious part of our California heritage."
The Delta fish decline has been unfolding since 2003, and a team of government biologists has been working for three years to understand the collapse. It has yet to find a smoking gun.
But the team identified a combination of factors that may have converged to imperil the fish, including excessive water diversions from the Delta, poor water quality caused by urban and farm runoff, and competition for food from invasive species.
"These are very discouraging numbers," said Marty Gingras, a member of the investigative team and a supervising biologist at the Department of Fish and Game. "We're trying to understand the mechanisms for the variations in fish abundance. If it turns out the actions of man are contributing, we may be able to undo that and improve conditions for the fish."
Environmental and fishing groups have argued for years that the contributing factors are all manmade, and they blame a sluggish government response for the death spiral.
The state and federal governments operate separate canal systems that divert Delta waters to urban and farm consumers from the Bay Area to San Diego. These water exports have reached near-record volumes over the past five years.
The pumping systems are strong enough to reverse natural flows in the Delta, sucking tens of thousands of fish to their deaths each year.
Government agencies in September lost a federal lawsuit filed by environmental groups that contested the pumping practices. The resulting court order requires water exports from the estuary to be reduced to protect the Delta smelt.
The first of those cutbacks began Dec. 29. Ultimately, urban water users from the Bay Area to San Diego who depend on Delta water could see their deliveries slashed as much as 30 percent this year. More than 2 million acres of farmland will be affected as well.
But water exports alone aren't to blame. State regulators have been slow to protect water quality in the Delta, and Bill Jennings, executive director of the California Sportfishing Protection Alliance, said all Californians share some blame for their wasteful water habits.
He said we will all share in the consequences.
"I've always maintained that a world that is not safe for fish is probably not long safe for little boys and girls," Jennings said. "The tragedy is that what we're seeing could have been avoided with a little common sense and a recognition that there are limits to using these waterways as sewers and bleeding them of their water."
Solutions are in the works. State officials are simultaneously preparing a habitat management plan for the estuary and drafting ways to reconfigure the Delta to protect the environment and secure water deliveries. New operating rules also are being developed for the export pumps.
It remains to be seen, however, if these efforts will come in time. Just in case, officials also are scrambling to breed a refuge population of Delta smelt in case the species goes extinct in the wild.
Call The Bee's Matt Weiser, (916) 321-1264.
