FRESNO - A federal judge denied environmental groups' request for a temporary order to cut back water supplies sent to farms and Southern California, but asked both sides to reconvene so experts can present evidence about whether pumps in the delta are killing off a threatened fish species.

State and federal officials temporarily halted operations at pumping plants drawing from the Sacramento-San Joaquin Delta last month, but the pumps were switched back on when authorities found most of the delta smelt had moved past the pumps into the San Francisco Bay.

But in the last week, the Department of Water Resources found that state pumps killed more than 380 smelt, a silvery, two-inch long species considered a bellwether for the health of the delta, a vast ecosystem that also provides drinking water to 25 million Californians. Yesterday, 30 fish were ground up after being trapped in the pumps, according to the department.

"There isn't anybody in the courtroom who wouldn't agree that the species is in a critical stage," said U.S. District Court Judge Oliver Wanger. But, the judge said, the evidence does not show that "the last smelt in existence is at the pumps and their destruction will extinguish the species."

The Natural Resources Defense Council filed a request for a temporary restraining order on Tuesday asking that the federal courts force the bureau and the Department of Water Resources to follow an expert group's recommendation to reduce pumping, effective immediately.

Wanger denied that motion Friday.