Kilbrennan Lake rehabilitation aims to restore native trout

By GWEN ALBERS Western News Reporter

As a kid, Bill Garrison caught 10- to 12-inch rainbow and brook trout at Kilbrennan Lake.

"It was great," said Garrison, a Libby native whose parents annually took him to the Libby Rod and Gun Club Fishing Derby at the lake.

"You caught a lot of fish," said the 55-year-old from Yaak.

Black bullheads and perch stocked illegally over the years just about wiped out the trout and any good fishing at the 57-acre lake 10 miles north of Troy. People like Garrison quit fishing there.

Now Montana Fish, Wildlife & Parks will undertake a $75,000 to $125,000 project to rehabilitate the lake. It will include getting rid of the bullheads and perch, and stocking redband trout. FWP believes redband were once the lake's dominant species.

"If they get rid of the bullhead and perch, I think I'll fish there again," Garrison said.

Yaak Rod and Gun Club approached FWP about the lake's condition, said Jim Mayo, a board member for the club near the Dirty Shame Saloon.

"Kilbrennan used to be a fantastic family fishing lake," Mayo said. "Over the years, the trout fishing has deteriorated to almost nothing."

The black bullhead started to show up in the lake in the late 1960s and early 1970s, said Jim Dunnigan, a fish biologist with FWP in Libby.

"They're really tenacious critters," Dunnigan said. "You could almost wrap them up in wet burlap and they would live. The numbers were in relative abundance. Once they took hold, they increased dramatically in numbers and took over the fish community until the perch showed in 1995."

"After that, I think the perch were probably consuming the juvenile or larvae black bullheads," he continued.

Today, brook and rainbow trout numbers have decreased to near eradication, while stunted populations of black bullhead and yellow perch are very abundant.

FWP will implement a two-phased approach to rehabilitate Kilbrennan Lake.

The initial phase will include enhancing the spawning habitat in Feeder Creek, a major source of surface water entering the lake. It also will involve constructing a fish barrier on Kilbrennan Creek.

FWP maintains that a physical barrier on Kilbrennan Creek is needed to prevent non-native fish from colonizing the lake after the chemical treatment to get rid of black bullheads, perch and non-native rainbow and eastern brook trout.

The second phase will involve removing non-native fish from the lake, Feeder Creek, and a portion of Kilbrennan Creek.

FWP proposes using Prenfish, a commercial formulation that contains 5 percent rotenone as the active ingredient. Rotenone is obtained from the roots of several tropical plants and is highly toxic to fish but is of low toxicity to warm-blooded animals. It is often used in home gardens.

The risk that rotenone will enter and be mobile in groundwater is minimal. Although there are no domestic wells located within the project area, a single household on lower Kilbrennan Creek relies on Kilbrennan Creek for domestic water. FWP will consult with the landowner regarding this issue and provide a safe source of domestic water.

FWP will restock Kilbrennan Lake with redband trout after the effective chemical treatment. Stocking will likely take place next spring.

"Stocking will depend on availability (of redband trout). I'd guess up to 1,000 to 1,500," Dunnigan said. "We will give an evaluation for a period of two to five years to see how they perform."