Biologists aboard the research vessel Scrutiny sounded the alarm a year ago when their nets came up with the fewest young striped bass and delta smelt since annual surveys began in 1959.
A closer look found the populations of two other fish species, longfin smelt and threadfin shad, also had crashed. The populations had gone down before but never simultaneously.
The decline is continuing this year, even though abundant water in the system means the species should be thriving. The fish are considered harbingers of the health of California’s vast delta, which supplies water to two-thirds of the state’s 36 million residents.
“There’s a lot of people’s jobs and lives and economic well-being depending on moving water through the delta in an ecologically sound manner,” said Chuck Armor of the California Department of Fish and Game, one of the scientists aboard the vessel. “It’s hard to imagine a more important issue.”
The delta collects water from the Sierra and Cascade mountain ranges in a ribbon of rivers stretching from Mount Shasta to the Central Sierra Nevada. The natural network of rivers, flood plains and wetlands drains 42 percent of California’s land area and eventually winds its way to San Francisco Bay, forming the largest estuary and one of the most important ecosystems on the West Coast.
From farmers to city folk
Finding solutions also could have significant consequences for farmers and Southern California water users. Enormous amounts of delta water are diverted south through federal and state pumps to irrigate some of the world’s most fertile fields in the San Joaquin Valley and to satisfy the needs of Southern California’s ever-expanding population.
“We are at a critical threshold,” said Bill Jennings, who until recently headed the Deltakeeper environmental watchdog organization. “We are going to make decisions within the next year that are either going to fix the delta, or we are going to use it essentially as a way station to transport water to Southern California.”
More than 200 foreign species have invaded the delta’s many waterways, including a toxic blue-green algae, a spiny zooplankton that may be replacing more beneficial species, and tiny clams that filter water like armies of tiny vacuum cleaners and compete with fish for food.
Pesticides from farm fields and the pumps that are powerful enough to suck in young fish also are thought to be playing a role in the demise of the delta’s fish populations.
Over the past 150 years, the delta has been artificially engineered by pumps, pipes, levees, canals and chemicals as California has harnessed its power for shipping, farming and drinking water supplies.
Pumps as culprits?
Among the possible culprits is water pumping from the delta — either its increase to near-record levels the last three years or a shift in timing of peak pumping. The pumps are so powerful that they reverse the delta’s natural seaward flow and have been blamed for killing fish.
However, B.J. Miller, a consulting engineer for water users, said there is no statistical proof the pumping is to blame for the species’ decline.
Scientists had hoped to eliminate some potential culprits with this summer’s research into the delta’s decline, but that hasn’t happened. There could be a half dozen smoking guns, said Bruce Herbold, a fisheries biologist with the U.S. Environmental Protection Agency and a member of the scientific panel studying the decline.
“What is happening to the delta ecosystem is like the canary in the mine. It is a warning that we have perhaps gone beyond its limits,” said Lois Wolk, a Democrat from Davis who chairs the state Assembly’s Water, Parks and Wildlife Committee. “We cannot allow the delta to fail. That is simply not possible.”