2009 another bad year for Delta ecosystem
The latest survey of Delta fish populations shows another ominous dip.
Despite ramped-up regulations meant to protect Delta smelt, the imperiled fish that has come to symbolize the conflict between the Delta ecosystem and statewide water demands fell to a record low, beating out the previous year’s record low.
But the survey numbers, posted late Tuesday, show the problems are not restricted to Delta smelt, which some biologists believe are dangerously close to extinction.
Longfin smelt and young-of-the-year striped bass, a popular sport fish, both fell to their second-lowest measures ever. And the number of threadfin shad, a widely used baitfish, plunged last year.
“The Delta smelt numbers are disappointingly low but not too surprising considering dry year conditions,” said Peter Moyle, a UC Davis fisheries biologist and one of the leading experts on California’s fish.
Threadfin shad, he said, are plentiful upstream of the Delta. Their absence in the Delta reflects a shortage of food or other environmental problems in the Delta, but those fish should bounce back quickly once the underlying problem is solved, he said.
Delta smelt, however, are so few that they could have much more difficulty reproducing fast enough to recover their numbers, he said.
Government biologists said it was not surprising, given dry conditions, that the Delta smelt numbers have not rebounded in response to new federal regulations on water
deliveries. Those restrictions are meant only to prevent Delta pumps from driving the fish to extinction and are not, by themselves, designed to lead to a full recovery of the fish.
“The fact that the fish are not extinct might mean (the regulations are) doing their job,” said Marty Gingras, a supervising fisheries biologist at the California Department of Fish and Game.
Still, the low measures increase the likelihood of water supply disruptions this year, because they will trigger tougher limits on how many fish can be killed before regulators intervene at the Delta pumps, which siphon water into canals that feed farms and cities around the state.
Once a certain number of fish are killed at the pumps, water managers will have to ask federal biologists for direction.
“We would consult with them as to what actions would be necessary at that time,” said Victoria Poage, a fisheries biologist at the U.S. Fish and Wildlife Service, the agency that wrote the rules after its old regulations were nullified in 2007 by a federal judge who found them inadequate.
Since 1967, state biologists have trawled for fish from September to December to measure the health of a half-dozen Delta fish species. The numbers show that since about the time the big Delta pumps started running, the numbers for all those fish have fallen dramatically.
The index used to measure Delta smelt numbers was typically in the hundreds and occasionally reached over 1,000. Now it’s at 17. For longfin smelt, the index regularly reached over 10,000 and now sits at 65. For striped bass, the number was well into the thousands 40 years ago and now is at 70.
Still, experts say the problems are not limited to Delta pumping.
The Contra Costa Water District, for example, has found a strong connection between Delta smelt numbers and the saltiness of Delta water during the fall months. The connection points to the possibility that salt-tolerant clams that have moved into the Delta are filtering out food that small fish need.
Among the factors contributing to the increased fall salinity is the way state and federal water managers operate upstream dams and Delta pumps, which has resulted in less fresh water flowing through the Delta in the fall.
Discharges into water upstream of the Delta, particularly from Sacramento’s large sewer treatment plant, are also being considered as possible culprits.
Mike Taugher covers the environment. Contact him at 925-943-8257.