Remember a decade ago when Montana Fish, Wildlife and Parks wanted to kill the westslope cutthroat trout in several Flathead South Fork lakes in an attempt to preserve their native genetics?
While FWP fisheries biologists believed the project was not only justified but also necessary, there was no shortage of opposition, especially from local anglers.
According to Matt Boyer, FWP mitigation specialist, westslope cutthroat trout, originally described by Lewis and Clark in Montana in 1805, had declined to occupy less than 10 percent of their historical range in the U.S.
Reasons for decline included habitat loss, competition and predation from other fishes, but most importantly, hybridization with rainbow trout.
Over 50 percent of current westslope cutthroat habitat in Montana is in the Flathead South Fork, a drainage where lakes have been stocked with rainbows from 1920-1960.
The Westslope Cutthroat South Fork Conservation Project was initiated in 2007.
The project was funded primarily by Bonneville Power Administration through Hungry Horse Dam mitigation. Additional resources were provided by FWP and U.S. Forest Service.
No tax dollars were used.
After extensive study, and working on only a couple lakes per year, some lakes were poisoned with rotenone, others were “genetically swamped”, meaning over-planted with genetically pure fish.
Lakes receiving rotenone treatment were studied 2-3 years both before and after treatment to assess any negative effects on invertebrates and amphibians. None were detected.
The year following rotenone application, those lakes were stocked with 2”, 6” and 12” genetically pure trout.
The larger fish are catchable and would spawn the following year.
Handkerchief Lake, chemically treated in 2016, also serves as a genetic reserve population site for Arctic Grayling.
The rotenone phase of the Project ended in fall 2017 with treatment of Sunburst Lake.
I applaud Region One FWP for their vision and perseverance in this project.
Jerry Smalley’s Fishful Thinking column appears weekly in the Hungry Horse News.