The Bush administration announced Tuesday that it will not remove dams on the Columbia and Snake river system to save endangered salmon.

The announcement rules out what the federal government had once described as the most scientifically sound -- if politically problematic -- method for saving salmon in the heavily dammed river system.

As recently as four years ago, the federal agencies responsible for enforcing the Endangered Species Act had said, "Breaching the four lower Snake River dams would provide more certainty of long-term salmon survival and recovery than would other measures."

But Tuesday in Portland, Ore., the leaders of those same agencies announced that they have determined how to operate the dams in a way that "will not jeopardize fish."

"Our work shows that you can achieve recovery without removing the dams," said Bob Lohn, northwest regional administrator for the National Marine Fisheries Service.

The primary new tool for protecting young salmon as they migrate to the sea, Lohn said, would be the installation of removable spillway weirs that guide fish safely through dams.

The announcement angered environmental groups, which have repeatedly sued the federal government over the past two decades and forced major changes in the way it operates the country's largest federally built hydroelectric system.

"By suggesting that the dams do not jeopardize fish, the Bush administration is contradicting decades of experience and volumes of their own scientific data," said John Kober, wildlife program manager of the National Wildlife Federation, the lead plaintiff in a lawsuit over river operations that is before a federal judge in Portland.

Kober said that removable spillway weirs "are techno-fixes that provide very minimal survival benefits."

He also noted that President Bush, on campaign swings through the region, has repeatedly insisted that dams on the Snake River are crucial to the economic life of the Pacific Northwest and that he would never allow them to be breached.

"Federal officials are trying to fulfill the president's campaign promises," Kober said.

Polls show that wild salmon remain an important cultural icon in the Pacific Northwest but also that jobs and economic concerns are far more important to voters this year.

In Portland, Lohn said that "a very strong positive uptick" in the numbers of returning adult salmon in the Columbia and Snake rivers shows that federal fish-recovery efforts are finally working.