By Laura Zuckerman
SALMON, Idaho (Reuters) - The U.S. Fish and Wildlife Service proposed on Tuesday actions needed to support imperiled bull trout, an iconic native fish that is still found in pristine, cold-water streams and some lakes in Idaho, Montana, Nevada, Oregon and Washington.
The proposed measures, which will stay open for public comment until July 20, divide threatened bull trout in the mainland United States into six areas targeted for recovery and seek to tailor conservation efforts to the specific challenges facing fish in waters from east central Idaho to southern Oregon.
The overall range of bull trout is thought to have decreased by as much as 60 percent when it was added in 1998 to the federal endangered and threatened species list, according to the Fish and Wildlife Service.
Threats include warming streams tied to climate change, impassable dams and destruction of their habitats by activities ranging from livestock grazing to road-building associated with logging and mining operations.
Measures designed to bolster the fish came after conservation groups filed a legal challenge alleging the Fish and Wildlife Service violated the Endangered Species Act by failing to finalize a recovery plan spelling out the actions it would take to prevent the fish from going extinct.
The Fish and Wildlife Service said the numbers of bull trout, which can weigh as much as 32 pounds (15 kg) and which depend on clean, cold water for survival, have not been thought to have declined since coming under federal protections.
Population trends in certain core areas in the five states, however, are not known because of gaps in monitoring, federal biologists said.
Conservation actions in mountain streams found in ranching areas such as Salmon, Idaho, include identifying and circumventing barriers to the fish's passage upstream to colder waters with spawning habitat.
Such barriers can include temporary dams used to divert water for crop irrigation and the blockages can be overcome by construction of a series of graduated pools, government biologists said.
Recovery efforts do not include northern California waters that once contained thriving populations of bull trout but which no longer support them.
The Fish and Wildlife Service is expected to issue a final recovery plan in September.
(Editing by Curtis Skinner and Muralikumar Anantharaman)