After tossing the trawl nets and tallying the numbers, the agency found a record low population of longfin smelt in the Pacific Coast’s largest estuary. Populations of Sacramento splittail, American shad, striped bass and the threatened Delta smelt also neared their lowest since the annual fall survey began in 1967.
“These data are just one more clear indication that the overall ecosystem of the Delta is in dire straits,” says Christina Swanson, senior scientist at The Bay Institute, a nonprofit that protects the San Francisco Bay. “Longfin and Delta smelt are teetering on the brink of extinction. They could be gone next year.”
The state’s Department of Fish and Game agrees that the fish are in serious trouble. “We’re very concerned about the trend that these data indicate,” says Marty Gingras, supervising biologist. The department says it cannot determine exactly how close to extinction the five species are, because the survey compares current fish populations to past abundance rather than providing a precise tally of the number of fish. Nonetheless, says Gingras, “there is merit in listing longfin smelt under the California Endangered Species Act, and uplisting the Delta smelt from threatened to endangered.”
A major factor harming the Delta’s fish is the overdraft of water from Delta watersheds. State and federal records indicate that water project diversions, which supply 24 million Californians and a $31 billion dollar agricultural industry, gulp an average of nearly 2 trillion gallons of Delta water per year. That’s more than half of the water that trickles into the Delta in a dry year, and 20 to 30 percent of total flows in a wet year.
“Clearly these data are confirming that we regularly take too much water out of the Delta and rivers,” says Swanson. The Bay Institute recommends that the state consider higher water efficiency, better management of groundwater, and water recycling to ease Delta demand.
Other problems threaten the Delta’s fish as well. Non-native species, such as the overbite clam, tend to out-compete natives and create less suitable habitat for them. Additionally, the water contains unhealthy levels of herbicides and pesticides from upstream agriculture and ammonia from sewage.
Habitat loss is another important factor in the Delta. Over the past 150 years, most of its marshes and waters have been leveed, drained and rerouted for agricultural and urban development.
A recent court ruling may provide some relief for the Delta’s fish. Last August, U.S. District Court Judge Oliver Wanger of California’s Eastern District imposed restrictions on export pumping from the Delta after ruling in favor of environmental groups. The groups had sued the U.S. Fish and Wildlife Service for failing to protect the federally listed smelt. Until the agency completes a new biological opinion on Delta management, the smelt and their ecosystem remain under interim protections.