Washington ? In a move that may block changes to the Missouri River’s flow, the Bush administration yanked the government scientists and is bringing in a new team.

The U.S. Army Corps of Engineers, which has resisted making changes to how it manages the river, is under a December deadline to come up with a new operations plan that follows the Endangered Species Act.

Now, a different team of scientists at the U.S. Fish and Wildlife Service will say whether the corps can avoid major changes — such as a previously ordered switch to a more natural spring rise and low summer flow — and still comply with the act.

“The corps is legally obligated to make these flow changes because the Fish and Wildlife Service has said it needs to do so,” said Tim Searchinger, an attorney for the conservation group Environmental Defense. “What appears likely to happen is that the Fish and Wildlife Service will have its mind changed for it.”

The Fish and Wildlife Service said critics were jumping to conclusions.

“Obviously, that’s prejudging what’s going to happen here,” said Hugh Vickery, a spokesman for the Interior Department, which includes the service.

It’s the latest development in a long-running battle over management of the nation’s longest river, which stretches 2,341 miles from Montana to St. Louis, where it empties into the Mississippi.

The old team of scientists said three years ago the Missouri needed a more natural spring rise and low summer levels to comply with the ESA, and their findings were confirmed by the National Academy of Sciences. Current operations were put into place before the river’s sturgeon and shorebird species made the government’s threatened and endangered species list.

But the corps resisted, and the Bush administration postponed the changes and is seeking a new “biological opinion” from the wildlife service. This process began during legal wranglings last July that resulted in a contempt citation of the corps from a federal judge who ordered the changes; the court action was subsequently postponed.

Vickery said one of the new team leaders, Robyn Thorson, was regional director of the Service’s Big Rivers-Great Lakes region in Minnesota, which includes a portion of the Missouri. The other leader is Dale Hall, regional director of the agency’s Southwest Region in Albuquerque, N.M.

Conservation groups reacted angrily to the maneuvering, saying the administration was obviously trying to avoid changing to a more seasonal ebb and flow to benefit birds and fish.

“In a month’s time, a group of people that knows nothing about the Missouri are supposed to write a credible biological opinion? Give me a break,” said Chad Smith, spokesman for the group American Rivers.

Smith said the U.S. Fish and Wildlife Service’s decision to bring in a new team of scientists would erase more than a decade of expertise on the waterway and its native species.