BILLINGS – Montana Fish, Wildlife and Parks, with assistance from Gallatin National Forest, planned to remove non-native trout from two creeks in the upper Boulder River drainage south of Big Timber during the first week of September.

According to FWP fisheries biologist Jeremiah Wood, biologists were set to treat Fourmile Creek and the lower three miles of Meatrack Creek with rotenone, a fish toxin that will remove all fish from the streams. Later in September, biologists will plant native Yellowstone cutthroat trout in both streams.

According to an FWP press release, rotenone at treatment concentrations poses no threat to people or animals; however, the agency asked people to refrain from recreating in or drinking from the creeks during the treatment.

Fourmile Creek runs out of Silver Lake on the west side of the upper Boulder River drainage and flows about seven miles before emptying into the Boulder River on the Gallatin National Forest. Meatrack Creek joins Fourmile Creek from the south about two thirds of a mile above the Boulder River. The trailhead leading to the two creeks is about 40 miles south of Big Timber near the end of the Forest Service road up the main Boulder River.

The reasoning behind the rotenone treatment, according to the release, was that the cutthroat’s continued existence is threatened in many areas of the state by non-native brook, rainbow and brown trout, which compete for food and habitat and prey on young cutthroats. In addition, rainbows crossbreed with cutthroats, and the resulting hybrid dilute the genetic purity of the native populations.

The project on Fourmile and Meatrack creeks is part of an ongoing project to remove rainbow trout and restore genetically pure native Yellowstone cutthroat trout in tributaries to the upper Boulder River. A long, steep cascade near the mouth of Fourmile Creek will inhibit rainbows from the Boulder River from repopulating the two treated creeks, Wood said.