Handkerchief Lake in line for fish treatment this fall

This fall, Handkerchief Lake is slated to become a genetic reserve for two imperiled fish native to Montana — westslope cutthroat trout and the only remaining Arctic grayling indigenous to the lower 48.

Located east of Jewel Basin, the popular fishing area is this year’s focus for the state’s 10-year effort to conserve genetically pure westslope cutthroat trout in the South Fork Flathead River drainage.

Along with Sunburst Lake, it’s one of two lakes left in the project, which is on schedule to wrap up in 2017. The South Fork drainage provides about half of the remaining interconnected habitat for the cutthroat species.

Montana Fish, Wildlife and Parks classifies native westslope cutthroat trout as a “species of concern,” due in part to their mating habits. Crossbreeding with introduced rainbow and Yellowstone cutthroats has for decades compromised the fish’s dwindling gene pool.

Handkerchief Lake has a longer fishing season thanks to its relatively low elevation and is easily accessed via nearby forest roads.

“It’s a popular fishery, and it’s going to be on the public’s radar,” Matt Boyer, the agency’s regional science program supervisor, said last week.

The project has generated controversy in the past. Wildlife officials use rotenone, a toxin that inhibits gill-breathing animals’ ability to absorb oxygen, to wipe out existing fish in lakes where other techniques are not viable. The agency then stocks the empty lakes with genetically pure westslope cutthroats.

Since it began in 2007, however, Boyer said the program has emerged as a success story. Rotenone treatments have had minimal impacts to other aquatic fauna and flora, and breeding populations of trout have been re-established in each lake treated thus far.

“The whole dialogue concerning this project has certainly evolved through time,” Boyer noted. “This was a contentious project.”

ROTENONE treatment in Handkerchief Lake also will remove one of the region’s few Arctic grayling populations, which were introduced into the lake decades ago.

But Boyer sees it as an opportunity to also create a genetic reserve for the struggling grayling populations native to Southwest Montana.

“Grayling aren’t native to the South Fork, but this was a situation where we’re considering social values as well,” Boyer said. “The public made it clear that they wanted to see grayling back in that lake, and biologically we felt that was a beneficial thing to do.”

Matt Jeager, a fisheries biologist with the state agency’s southwest region, is overseeing the effort to create what he calls a “genetic reserve brood” of Montana Arctic grayling — the first of its kind outside Southwest Montana.

“In the Lower 48, historically there were only two populations of grayling: one in Michigan and one in Montana. The one in Michigan was extirpated some time ago,” Jeager said. “It’s a really unique fish. I think what attracted Boyer and some of the folks that were working on grayling up there is that it has a very unique conservation value to it. It’s important on a lot of different levels, not just as a recreational fishery, but it has a conservation value to the whole state.”

Today, only about 20 lakes in the Centennial, Big Hole and Ruby valleys contain Montana Arctic grayling, also known as “red rock” or “Centennial” grayling.

“If something were to happen in the Centennial Valley, say the population crashes, or there’s a wildfire or catastrophic drought, we can go back to these genetic reserve broods and use them to either augment or re-establish the populations,” Jeager said.

He conceded that the agency’s prior attempt to create a genetic reserve in Elk Lake near West Yellowstone has failed to re-create a viable population. The lake has just one tributary, and coupled with long-term drought, it has remained inaccessible to the grayling during their spawning season.

With a more reliable inflow, fisheries biologists believe Handkerchief Lake will present a solution to that problem. Rotenone treatment will take place this fall, with restocking beginning next spring.

“It’ll take a few years before the largest fish are back in the population, but the size and the length of those fish will be no different,” Boyer said. “This is an effort, in part, to conserve a piece of Montana’s heritage.”

Reporter Sam Wilson can be reached at 758-4407 or by email at swilson@dailyinterlake.com.