Delta fish continue to hover at the brink of extinction, and conditions could worsen for the estuary and the economy unless winter gets a lot wetter, according to a state survey.
Native delta smelt, a threatened fish, is at its lowest point in 42 years of record-keeping. Two non-native fish, the American shad and threadfin shad, also set record lows.
The findings were in the state Department of Fish and Game's latest fall population survey of delta fish species, which concluded in December.
Three other species showed slight gains over 2007 but remain well below historical averages: the native longfin smelt and Sacramento splittail, and the non-native striped bass. Even though the survey found no splittails last fall, and just one in 2007, officials say the fish isn't often found in the areas netted and that some previous counts likewise have not detected them.
"When the uncommon ones like delta smelt and the common ones like threadfin shad both take a nose dive, there's something really wrong," said Bruce Herbold, a biologist who monitors the delta for the U.S. Environmental Protection Agency. "We're really seeing a massive change."
The Sacramento-San Joaquin Delta's health is of concern because it is a freshwater source for two-thirds of California's population and millions of acres of farmland.
Last year, delta water diversions were slashed by about 30 percent to protect fish, bringing a hit of at least $300 million to the economy, according to an estimate by the state Department of Water Resources.
It could get worse this year.
In December, the DWR warned water contractors that they might get only 15 percent of average delta water deliveries because of the drought.
On Wednesday, a DWR planning committee reported that the delivery forecast may shrink further, perhaps as low as 5 percent to 9 percent of average.
It is rare to see that forecast shrink midwinter. It usually grows as storms deepen the Sierra snowpack.
But as DWR Deputy Director Ralph Torres noted, California has seen little precipitation since December and needs a deluge to refill reservoirs.
The report was obtained by The Sacramento Bee before its official release. Torres said a new delivery forecast has not been made, but he confirmed it likely will be less than 15 percent.
"Originally we had planned on doing that (new forecast) by Feb. 15," Torres said. "But we may move that date up because we don't think any precipitation between now and then is going to change anything."
The water content of the statewide snowpack stood at 57 percent of normal Thursday. Oroville Reservoir, the main supply for the State Water Project, has nearly reached a record low level.
The report suggests that California's water supply is on a path to match the two worst droughts in state his- tory: 1923-24 and 1976-77.
Could things get that bad? "It's probably a scenario we have to consider," Torres said.
This could worsen conditions for struggling delta fish species and for water quality.
Biologists warn that the delta is in the midst of a human-caused shift to a different kind of aquatic habitat, one that holds risks for human and environmental health.
The estuary is changing, they say, into a warmer and more stagnant water body where toxic algae blooms are common. Sea- sonal shifts in temperature and salinity that once defined and cleansed the es- tuary are disappearing.
Causes are many, experts say, including urban and agricultural pollution and the introduction of thousands of foreign wildlife species. The delta has also been managed for decades as a freshwater delivery tool serving the world's eighth-largest economy, ahead of the needs of wildlife and water quality.
"You put them together and you get what I'm calling a train wreck," said Bill Ben- nett, a University of Cali- fornia at Davis fisheries ecologist and and delta smelt expert.