Delta Smelt Deaths Raise Concerns : Environment: Surge in mortality among endangered fish indicates new safeguards are not adequate, official says.

A sudden, dramatic rise in the mortality of the threatened delta smelt has sounded a new alarm about the biological degradation of the Sacramento-San Joaquin Delta and San Francisco Bay just a few months after a new plan was adopted to protect the tiny fish’s fragile habitat.

Last week, officials of the U.S. Fish and Wildlife Service and the California Department of Fish and Game began to find that smelt were dying at up to five times the maximum daily mortality rate the species can survive. Listed as “threatened” under the Endangered Species Act, the finger-size fish is regarded as a barometer of the ecological health of the delta.

“We had a whole series of protective measures in place, but what we’re seeing basically says those measures weren’t enough, at least not in the kind of critically dry year we have had,” said Bob Sweetnum, a biologist with the Department of Fish and Game.

Home to 400 fish and plant species, the delta is one of the largest and richest estuaries on the continent and is also the source of most of the state’s drinking water and irrigation supplies. The estuary is sustained by the brackish mixture of saltwater and freshwater. But as pumping from the Sacramento and San Joaquin rivers has diverted fresh water for agriculture, industry and urban growth, excessive salt levels have degraded the estuary and reduced its levels of spawning fish and wildlife.

The Clinton Administration has proposed a stringent set of rules to protect the delta by restoring an average of 540,000 acre-feet of water per year. Although that plan has not taken effect, the Fish and Wildlife Service issued an opinion in February regulating minimum freshwater flows into the delta and setting limits for the number of smelt that can be killed.

Bob Pine, a biologist with the Fish and Wildlife Service who worked on the opinion, said there had always been a concern that the prescribed freshwater flows would not be enough in an exceptionally dry year.

“We tried to put together a biological opinion that would deal with the survival of the smelt and fulfill state and federal water contracts. But we couldn’t come up with a formula for a critically dry year.”

A coalition of environmental groups filed a lawsuit in February, arguing that the protections under the opinion were not adequate. On Thursday, David Behar, director of the Bay Institute, one of the groups that filed the suit, said that the recent mortality rates--as high as 4,000 fish a day--were proof that the level of protection was not sufficient. But Behar also said that state and federal officials violated the opinion by failing to reduce freshwater diversion when the number of dead fish began to exceed the maximum limits set by the opinion.

The smelt die when they are sucked into the pumps that divert the water. The smelt thrive in the delta’s mixing zone where freshwater and saltwater meet. As pumping increases, that zone moves east toward the pumps and the smelt move with it.

Bob Potter, chief deputy director of the California Department of Water Resources, said that pumping is 10% of what it was last week when the high fish kill was reported. He said the level would remain low for the next few days while officials try to come up with a solution. But he said there was no way the state could maintain those low levels for more than a few days and meet its obligations to water users.

Potter also held out the possibility that the high mortality rate reflected an usually high number of smelt. “It could mean that the biological opinion has provided enough flow to grow a zillion fish.”