The U.S. Fish and Wildlife Service decided against listing the Bonneville cutthroat trout as threatened or endangered in 2001, then withstood a legal challenge to the decision last year. Now a new agency rule is causing biologists to take another look at the cherry-cheeked fish that swims mostly in Utah high country.

It doesn't mean the trout have declined in the last year, but rather that biologists now have orders to consider whether it's endangered in any significant swath of its range - not whether the entire population is at risk.

State biologists welcome the study but say they believe recovery efforts are working. The fish was in just 35 percent of its historic range at last count, but habitat improvements and removal of non-natives have led to expansion, said Roger Wilson, cutthroat trout program coordinator for the Utah Division of Wildlife Resources.

"They're doing pretty well in a lot of areas," he said. "The trajectory is in a positive way."

Cutthroats were an important food fish for American Indians and Mormon pioneers until commercial fishing, irrigation diversions and introduction of non-native competitors cut into their numbers. Some areas, such as Utah Lake, have never recovered from the assault.

Other areas, especially mountain streams far removed from large human settlements, kept a reservoir of the trout. One stream that still provides great - but regulated - cutthroat fishing is the Logan River, said Chris Thomas, a Logan resident and president of Utah Trout Unlimited.

"There are not a lot of them left, but they're fantastic fish for dry-fly fishing," Thomas said. "They'll readily take a dry fly. And they're just beautiful fish. You can just tell they're wild."

The Bonneville cutthroat has spotted sides, often red cheeks and a colored slash under the gills. That slash often is more orange than the blood-red versions on some of the species' western and northwestern cousins.

Thomas said his group favors the state's generally effective efforts to repopulate former trout habitat, and he's unsure whether federal listing will be necessary. But as housing and cabin development presses higher into alpine valleys, federal protection probably would require crucial setbacks from streams, he said.