Pumps, clams eyed as culprits in Delta species decline

By Mike Taugher
CONTRA COSTA TIMES
Tuesday, November 15, 2005

Scientists unveiled a pair of theories Monday that might help explain a grave ecological crisis in the Delta, identifying possible culprits as unassuming as a small clam and as prominent as the giant pumps that ship trillions of gallons of water a year to the south.

Neither theory can fully explain the problem, which involves a sharp decline in several Delta fish species during the past three years that experts so far are at a loss to understand.

But together, they might.

For months, scientists have been looking at recent increases in the number of clams in Suisun Bay, an important rearing area for Delta smelt and other fish. The overbite clam, which arrived from Asia in ship ballast around 1986, is a prodigious filter feeder that can carpet the bay's floor with 10,000 tiny clams in an area just 3 feet by 3 feet.

Colonies of the clams are capable of filtering all of the water above them in a day. They could be cleansing the bay of the fishes' food.

More recently, scientists realized that the giant pumps that supply Delta water to the San Joaquin Valley and Southern California are, in recent years, killing unusually high numbers of fish during the winter months.

Winter previously received far less attention than spring, when major changes have been put in place to protect fish eggs, larvae and migrating juvenile salmon from the effects of pumping water out of the Delta.

But fish killed in the winter are adults ready to spawn, meaning the loss of a single fish means hundreds -- or thousands -- of eggs never get released And, as a result of trying to protect fish in the spring, the pumps are ru= nning harder in the winter.

U.S. Environmental Protection Agency biologist Bruce Herbold said the high winter fish-kill numbers were overlooked until he tried to figure out what time of the year threadfin shad turned up in the pump facilities.

Because the shad was a very common fish that was in rapid decline, Herbold was particularly interested in why that fish species was plummeting.

"It just leapt out that the take of threadfin shad had skyrocketed (in the winter months)," Herbold said.

He began looking at other fish species and found several troubling developments in the numbers. Not only was the winter fish kill at the pumps going up at a time when the overall populations were extremely low, but the concentration of fish was higher.

In other words, for some reason, pumping 1,000 gallons in the winter was killing more fish than pumping 1,000 gallons in other months.

B.J. Miller, a consultant for San Joaquin Valley water users, said the number of fish killed at the pumps was not enough to affect the overall populations of fish.

But Herbold said the new information will be more fully investigated next year.

The theories were unveiled at a forum in Sacramento to present the results of the first year of a scientific investigation into the cause of the ecological decline, which has affected major fish populations in the open-water zones.

Today, an independent panel will comment on the results of this year's work and help make recommendations for next year

In January, scientists confirmed an ongoing decline of Delta smelt, young striped bass, threadfin shad and longfin smelt. The results were surprising because the fish were all declining at the same time, beginning about three years ago when rain and snow patterns were favorable for the fish.

Scientists are convinced something profound has changed, but there are so many possibilities about what might have gone wrong they remain unconvinced that they have found any satisfactory answers.

The crisis has grabbed the attention of scientists, environmentalists and state policymakers.

San Joaquin Valley farm districts and Southern California water agencies are also concerned because of the potential that the problem could affect the availability of water.

Adding to the frustration was the fact that the crisis developed in the middle of a $3 billion-and-counting effort to improve conditions in the Delta and state water supplies.

The first-year scientific effort cost about $1.7 million. Further investigations next year are expected to cost about $3.25 million.

In addition to theories involving the loss of food for rearing fish in Suisun Bay and the death at the pumps from pre-spawning adult fish, several other potential problems remain under consideration.

For example, two power plants near Antioch are capable of pumping huge volumes of water for cooling. They release warmer water into Suisun Bay. That water potentially could contain pollutants.

State officials are investigating but said they have not received all the information they would like from Mirant, the owner of the power plants.

"They weren't very cooperative," said Zoltan Matica, an environmental scientist at the Department of Water Resources.

Another possible culprit is a toxic algae that began appearing in recent years. The algae is the first toxic algae to bloom in the Delta, a drinking water source for more than 22 million Californians, including nearly 500,000 people in Contra Costa County.

Microcystis aeruginosa can cause cancer in wildlife and in humans, but water agencies so far say they have not detected the algae at levels high enough to cause concern in water entering treatment plants. Contra Costa water officials said they have never detected it in water leaving its treatment plants.

Mike Taugher covers natural resources. Reach him at 925-943-8257 or mtaugher@cctimes.com.

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