Outlook for Delta smelt at new low
STOCKTON - A new, record-low number of Delta smelt is prompting some scientists to wonder if the entire species of the bellwether fish is heading belly-up. The 2- to 5-inch, translucent blue fish - often used to gauge the Delta's overall health due to its sensitivity to its environment - is at the lowest numbers in history, according to one measuring stick used by the state. The smelt population has dropped to a third of the number recorded in 2004, according to a Fish and Game survey last month. The 2004 numbers were already the lowest since the state began tracking the fish in the 1960s. "I would say most scientists who work with these fish are convinced that the species is at great risk of extinction within the next couple of years, based on these numbers," said Tina Swanson, a biologist with the San Francisco-based Bay Institute. The fate of the already-threatened species is linked to the massive water systems that deliver Delta water to 23 million Californians, most in the southern San Joaquin Valley and Southern California. Export pumps near Tracy are sometimes turned off because they kill large numbers of smelt. The populations of smelt and several other fish species in the Delta have been declining for several years, prompting a large research effort by a team of government and academic scientists last year. Initial results fingered water exports and invasive species as possible causes, although pollution is believed to be another factor. Fish and Game biologist Chuck Armor said the latest smelt numbers place even greater pressure on finding answers. "It basically says that we can't let up," he said. University of California, Davis, scientist Bill Bennett said he believes the smelt are headed for extinction. Rising water temperatures and time could deal the final blow, he said. The fish don't survive well in water warmer than about 66 degrees Fahrenheit, he said, and Delta waters during the summer already approach that temperature. "Given the inevitability of global climate changes, it's likely that the Delta-Suisun Bay environment will simply get too warm for the fish," he said. Losing the species may not have a significant impact on the Delta, Bennett said. But finding answers to the smelt's decline is still important. The fish is unusual because it lives for only a year and lays relatively few eggs compared with other fish. "There's an awful lot we can learn about the Delta environment by studying this fish," Bennett said. It's also important because many people will blame water exports if the smelt die off, he said. In 1993, the Delta smelt became a threatened species under the Endangered Species Act when the fish were found dying in water pumps near Tracy. Some scientists have tied increased water exports to the fish's decline. But the effect of water shipments won't tell the whole story, Bennett said. "The truth is going to be a lot muddier than that," he said. Swanson, however, said exports are something that officials have some control over. "It's a knob that you can turn that lets you change the system," she said. "There's not nearly enough knobs to manage invasive species, .. but for exports, you have something you can change." . She said the latest smelt numbers are prompting more talk of extinction, but there may still be time to do something. "I'm not optimistic," she said. "On the other hand, I'm not completely writing these fish off. ... I think it's going to take a real concerted effort." Contact reporter Warren Lutz at (209) 546-8295 or wlutz@recordnet.com
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