Handkerchief Lake next in line for fish treatment

Anglers have one last week of limitless fishing on Handkerchief Lake before Montana Fish, Wildlife and Parks sterilizes the lake as part of its ongoing westslope cutthroat trout conservation project.

Beginning Sept. 12, the state wildlife agency will close down Forest Road No. 897 and the Graves Bay and Handkerchief Lake campgrounds to allow wildlife biologists to treat the alpine lake with rotenone, a toxin that targets gill-breathing animals.

Next summer, the agency will restock it to create a genetically pure reserve of westslope cutthroat trout and Arctic grayling.

Handkerchief Lake lies just above the west side of Hungry Horse Reservoir and is one of the last lakes to be targeted for Fish, Wildlife and Parks’ 10-year conservation project in the South Fork Flathead River drainage. The region’s westslope cutthroats have seen their gene pool compromised by hybridization over the years with non-native trout species, including rainbows and Yellowstone cutthroats.

Scientists are also using Handkerchief’s status as a popular grayling fishery to help conserve the dwindling population of grayling native to the Treasure State. While Arctic grayling are more common farther north, the Lower 48 states historically had only two populations: one in Montana and a now-extirpated population in Michigan.

“In addition to resetting the recreational fishery, both the cutthroat and the grayling that are going back in there will have conservation value as well,” Matt Boyer, the state’s regional science program supervisor, said.

According to Matt Jeager, a fisheries biologist for the state agency’s southwest region, the grayling are currently limited to about 20 lakes in the Centennial, Big Hole and Ruby valleys. In an interview earlier this year, he said replacing the existing non-native grayling in Handkerchief Lake will create a “genetic reserve brood” that could be used to augment the existing fisheries should their numbers decline due to a drought, wildfire or other event.

Boyer said the timing of the restocking is dependent on hatchery schedules, but he hopes to begin getting fish back in the lake as early as June. The agency will stock multiple age classes, meaning anglers can start fishing immediately thereafter.

“Both the cutthroat and the grayling, the largest fish will be six to eight inches in the first year,” Boyer said. “Handkerchief is one of the more productive lakes in the South Fork, so I would expect growth rates to be pretty good.”

He added that the Red Rocks grayling grow to about the same size as those currently stocked in the region, so anglers shouldn’t notice much difference between the two fish.

The conservation project will continue next year with the treatment of Sunburst Lake — just northeast of Swan Peak — and its restocking the following summer.

After the Sept. 12 closures, Forest Road No. 897 and the Handkerchief Lake Campground are scheduled to reopen to the public on Sept. 18. Graves Bay Campground, where the state agency will set up its operations, will reopen Sept. 23.

For more information, contact Sam Bourret at 751-4556 or by email at sbourret@mt.gov. Information on the conservation project can also be found online at bit.ly/2cb34Hp.

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