A subspecies of mountain whitefish that only exists within the Big Lost River drainage northwest of Arco has experienced a substantial decline in numbers, and the Idaho Department of Fish and Game is hoping to bring the species back.
As a first step toward recovering the fish, a freshwater member of the salmonid family, the Idaho Fish and Game Commission last week unanimously approved a conservation and management plan for mountain whitefish living in the drainage.
The commission made its decision during its quarterly meeting, held at the Sun Valley Resort from May 16-18.
Steve Yundt, fisheries chief for the Idaho Department of Fish and Game, presented the plan.
"We're concerned the fish not wink out," Yundt told the commissioners.
Chief among the plan's objectives is to maintain two spatially separated populations of at least 5,000 adult mountain whitefish each, one above and one below the Mackay Dam on the mainstem of the Big Lost River.
Above the dam, the plan calls for a distribution of the fish between the Chilly Slough diversion and the North Fork of the Big Lost River. It calls for a population in at least three of the following four tributaries: the North Fork of the Big Lost, East Fork of the Big Lost, Wildhorse Creek and Star Hope Creek.
In each of those spots, the plan calls for a population of at least 100 fish.
Below Mackay Dam, the plan calls for a distribution of fish in the Big Lost River downstream to the Blaine Diversion, and in at least one of the following two stretches: the Big Lost River between the Blaine diversion and the Moore diversion, and Antelope Creek between Marsh Canyon and Iron Bog Creek.
According to the Fish and Game plan, factors contributing to the decline of mountain whitefish subspecies include habitat alteration, passage barriers, dewatering, altered flow regimes, competition and predation from non-native fish, disease and exploitation.
Other factors include grazing and entrainment, or the accidental entrapment of fish in diversion ditches.
Among other things, the conservation plan calls for more population monitoring, maintaining a no-harvest rule until population goals are met and potential screening of diversion ditches.
However at least one environmental activist doubts the plan will work. Jon Marvel, executive director of the Hailey-based Western Watersheds Project, said it doesn't include any enforcement mechanisms or a dedicated funding source.
"It's completely voluntary," he said.
While mountain whitefish are distributed throughout much of the western United States and Canada, the Big Lost River drainage population is considered to be an endemic, or genetically divergent subspecies, Bart Gamett, south zone fisheries biologist on the Salmon-Challis National Forest, said in an interview.
Gamett works out of the forest's Lost River Ranger District headquarters in Mackay.
Based on mitochondrial DNA research, it's believed that the Big Lost River mountain whitefish moved into the river system some 165,000 to 330,000 years ago, Gamett said. The subspecies is considered most closely aligned with the Upper Snake River mountain whitefish, which is considered the parent stock, he said.
Today, the Big Lost River, like other streams and rivers in that isolated corner of Idaho, is cut off from the Snake River and sends its flows into the volcanic deserts to the south where they disappear beneath the ground.
Gamett has spent the past 12 years researching the Big Lost River mountain whitefish and its steady decline. His research contributed to the recently approved management plan.
Mountain whitefish in the Big Lost River drainage are suffering from a substantial decline in both their distribution and abundance, Gamett said.
"If nothing is done, extinction is a very real possibility," he said.
The species' tenuous situation is a far cry from years ago, when locals considered the then-abundant whitefish an excellent adversary for mid-winter fishing, he said.
Despite their troubling decline, however, Gamett said he was "very optimistic" that the subspecies can be restored.
Western Watersheds Project has taken a different route toward protecting the fish, asking that the subspecies be listed under the federal Endangered Species Act. The group petitioned the U.S. Fish and Wildlife Service to list it last June. The agency has not yet responded to the petition, even though it's legally obliged to do so within a year, Marvel said.
Within several weeks, the group is planning on filing a 60-day notice with the agency, which is a required step before a lawsuit can be filed, he said.