A multiyear project aimed at restoring native westslope cutthroat trout in alpine lakes above the South Fork Flathead drainage will resume next week when Necklace Lakes will be treated with a toxin to remove non-native or hybrid fish.

Like other lakes that have had similar rotenone treatments since 2007, the Necklace chain of lakes will be restocked with westslope cutthroats.

“All of the lakes that have been treated to date have been restocked and have been fishing well,” said Matt Boyer, the project leader for Montana Fish, Wildlife and Parks. “I’ve been getting reports from anglers.”

The overall project is aimed at 21 alpine lakes that have outlets flowing into the South Fork Flathead drainage, which is considered the best remaining stronghold for westslope cutthroats. It was initiated out of concerns that fish populations that have been hybridized with non-native rainbow or Yellowstone cutthroats would leak into the drainage over time, causing a proliferation of hybridization.

“We’re about halfway through the 21 lakes,” Boyer said.

The project started in 2007 with Black and Blackfoot lakes being treated in the Jewel Basin Hiking Area. In 2008, Lower Big Hawk Lake. Clayton and Margaret lakes were treated in 2009 and last year Wildcat Lake was treated.

“We’re documenting natural [westslope] reproduction in these lakes, which is a huge success,” Boyer said.

Six other lakes — Pilgrim, Upper and Lower Three Eagles, George, Woodward and Pyramid — have been genetically “swamped” with large numbers of westslope cutthroat fry for the last three years. It was determined from heavy stocking on those lakes in the 1980s that swamping can effectively suppress non-native fish populations.

“For those six lakes where it was effective, we decided to resume swamping,” Boyer said. “The management objective is the same.”

While past projects have involved the use of helicopters to haul in gear and a boat into the Jewel Basin, the project that gets under way Monday will involve using mules to pack equipment and an inflatable raft into the Bob Marshall Wilderness.

Necklace Lakes, located several miles northeast of Holland Lake, will be treated over the week along with a section of Smokey Creek, the outlet stream that flows toward the South Fork Flathead River.

During the project, Smokey Creek Trail 120 will be closed from Sapphire Pass to the junction of Big Salmon Creek Trail 110.

Reporter Jim Mann may be reached at 758-4407 or by email at jmann@dailyinterlake.com.