In the pre-dawn darkness, federal officials shut off water to Oregon farmers Thursday in order to save endangered fish, the latest event in the battle for Klamath Falls.

Ignoring catcalls from protesters, U.S. Bureau of Reclamation officials shut the bank of six headgates on the A Canal of the Klamath Project, then dismantled the operating mechanism so they cannot be opened again.

"Have some [courage] and walk off the job," Jeanne Hallmark of Klamath Falls yelled through a fence at four U.S. Bureau of Land Management rangers guarding the irrigation structure.

It was only the most recent time officials shut off the water, as angry farmers have forced the headgates open four times, the last time on July 4.

This time, farmers who organized a truck convoy that brought national attention to their fight for water had persuaded protesters not to storm the headgates, said Bill Ransom, a local businessman and farmer and one of the convoy organizers.

Chief ranger Felicia Probert said the headgates began closing at 5:10 a.m. and were shut within 20 minutes.

The government says it needs to shut off the water flow because endangered suckers in Upper Klamath Lake and coho salmon in the Klamath River face death if water levels don't remain at a certain depth. Last April, the Bureau of Reclamation shut off irrigation water to 90 percent of the 220,000 acres of the Klamath Project.

Farmers said the water cutoff would destroy their crops. The irrigation network was started in 1907 to irrigate the arid Klamath Basin, not to save fish, they said. They grew angry enough to open the headgates themselves.

In July, Interior Secretary Gale Norton authorized a limited release of water to farmers — less than 20 percent of the water provided in past years. Norton said at the time she hoped the release would help defuse the building tension.

Gavin Rajnus, a farmer from Malin, said the extra water released by Norton had helped green up some hay, but was too late to nurture his primary crop, potatoes.

"The best thing we can do is conserve our water for next year," Rajnus said. "There's no point to forcing the issue.

Wendell Wood of the Oregon Natural Resources Council, a conservation group that has battled to win water for fish and wildlife, said the fight was not between farmers and fish. Rather, he said, it's between the economic interests of farmers, commercial salmon fishermen, Indian tribes and businesses associated with the migrating waterfowl that stop at local refuges.

"What we are seeing in the Klamath Basin today foretells the history of much of the rest of this century," Wood said. "There's not enough water for everybody who wants it. We have to decide if salmon and bald eagles are more important than potatoes and sugarbeets."

The Associated Press contributed to this report.