Montana Plans to Bring Back Cutthroat Trout—By Removing Rainbow Trout

In Buffalo Creek, on the northern edge of Yellowstone National Park, rainbows are out and cutthroats are in. That’s what officials at Montana Fish, Wildlife and Parks and the Custer Gallatin National Forest agreed to when they recently approved the Buffalo Creek Yellowstone Cutthroat Trout Conservation Project.

The country’s first national park remains one of its most pristine ecosystems. But nonnative trout species—rainbow, brown, lake, and brook—all introduced near the end of the 19th century, have increasingly threatened native Yellowstone cutthroats. When lake trout entered the Yellowstone Lake system in the early 1990s, the cutthroat population crashed from 4 million to under 400,000, a decrease of 90 decrease. Lake trout—voracious predators and currently the largest fish in Yellowstone—remain in the park’s lakes to spawn, whereas cutthroat return to small stream spawning grounds. So, the demise of the cutthroat impacts a wide range of other species throughout the park, including osprey, eagles, otters, and black and brown bears, which feed on the fish. Thanks to the efforts of David Sweet—one of Field & Stream’s 2013 Heroes of Conservation—and many others, though, a gillnet program has been removing 300,000 lake trout a year from Yellowstone Lake and the cutthroat have rebounded.

Buffalo Creek, part of the Lamar River watershed, however, has a different history. Due to a barrier waterfall, it had never established a cutthroat population, even though its cold mountain waters represent perfect cutthroat habitat. The creek’s population of introduced rainbows, meanwhile, present a threat to the cutthroats below in the larger system due to cutt-bow hybridization. (Rainbows readily spawn with cutthroats, compromising the native fish’s genetic integrity.)

This new project will tap rotenone, a tree-based natural pesticide, to rid Buffalo Creek of the introduced rainbows over a five-year period. Then, native cutthroats will be released into the stream en masse. “The Buffalo Creek project is an important project for the long-term viability of the natural Yellowstone cutthroat trout in the Lamar River in Yellowstone National Park,” said Mike Ruggles, Montana FWP’s regional supervisor in Billings. “Currently, Buffalo Creek, a headwaters tributary of Slough Creek and Lamar River, harbors introduced rainbow trout and is the major contributor of rainbow trout to the Lamar River.”

The plan is to claim the formerly trout-less creek as a measure to increase cutthroat habitat in the face of climate change and the threat of nonnatives in the 352-mile system. Those who have previously submitted comments to the Forest Service in response to the plan have 45 days to submit written objections before final approval.