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Montana Purging Alpine Lakes Of Non-Native Fish To Preserve Cutthroat Trout Genetic Purity
Posted on Friday, October 01, 2010 (PST)

A project aimed at purging non-native fish from an alpine lake in the Jewel Basin Hiking Area in western Montana got under way Wednesday, with a helicopter flying in people and gear from a staging area in the Foothill Road area.


The Wildcat Lake project is part of a long-term Montana Fish, Wildlife and Parks effort to restore westslope genetic purity in the westslope cutthroat trout population in the South Fork Flathead Basin.


The work involves using a toxin called Rotenone to kill off the lake’s existing fish population, which includes rainbow trout and hybrid cutthroats, followed by restocking the lake with genetically pure westslopes next year.


A helicopter was used to fly in two boats and motors, along with 22 30-gallon barrels of Rotenone and seven people to carry out the work over a two-day period, said Matt Boyer, the project leader for Montana Fish, Wildlife and Parks.


Wildcat Lake covers about 40 acres, has a maximum depth of 112 feet and is located at the north end of the Jewel Basin on the Swan Mountain Range. It is the fifth lake to be treated over the last three years in the overall effort to maintain genetic purity of westslope cutthroats in the South Fork Flathead River basin, which is considered to be the stronghold for the species in Montana.


The alpine lakes were identified as a persistent source for hybrid fish leaking into the river drainage.


To prepare this week’s operations on the lake, Boyer and his crew packed into the area last week to treat Wildcat Creek below its outlet from the lake.


That involved setting up Rotenone drip stations along about 4 1/2 miles of the stream, along with a drip station to dispense a chemical to neutralize Rotenone at the lower end of the stream, where it joins Wounded Buck Creek.


“The detox part of this was key because Wounded Buck is a bull trout spawning and rearing stream,” Boyer said.


Test fish in cages were used to verify that no Rotenone entered Wounded Buck Creek.


“We were successful in containing it,” Boyer said, noting that a similar approach will be used this week to ensure that none of the Rotenone in the lake gets into Wildcat Creek.


The other major component to the overall project is the work to restore the fisheries. Black and Blackfoot lakes were treated in 2007 followed by Big Hawk Lake in 2008 and Margaret and Clayton lakes in 2009.


“These lakes are important recreational fisheries. In all the lakes we’ve restocked, we’ve seen natural reproduction already,” said Boyer, noting the exceptions of Margaret and Clayton Lakes, which were treated just last fall.


Once the ice comes off in the early summer, catchable cutthroats ranging from 6 to 12 inches are flown in, and cutthroat fry are planted in the lakes for the following three to five years.


Boyer said he’s gotten reports of successful fishing from anglers who have been to the lakes.


“In terms of fishing, you don’t miss a beat,” Boyer said. “I’ve fished Blackfoot and Lower Big Hawk myself and had good days of angling.”


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