April 27, 2022
By Joshua Bergan
A rainbow trout stronghold amidst important Yellowstone cutthroat trout habitat in both Yellowstone National Park (YNP) and Montana’s Absaroka-Beartooth Wilderness has been approved for a controversial non-native trout removal project starting in August 2022.
The project proposes to use the piscicide rotenone to poison and remove non-native rainbow and cuttbow trout in Buffalo Creek, which has been identified as the main source of rainbow trout causing hybridization in Slough Creek cutthroat. Buffalo Creek dumps directly into Slough Creek, but its rainbow trout population has to the potential to hybridize well beyond Slough and seriously threaten crucial habitat.
“Rainbow trout breed with cutthroat trout yielding fertile hybrids that continue to spread nonnative and harmful genes through a population, and if left unchecked, this hybridization threatens the entire Lamar River population of cutthroat trout found in 352 stream miles in the basin,” said Carol Endicott, Montana Fish Wildlife and Parks (FWP) Fisheries Biologist, in the “Reclamation of Buffalo Creek for Yellowstone Cutthroat Trout Final Environmental Assessment.”
FWP plans to subsequently stock native Yellowstone cutts into the Buffalo Creek basin once non-native trout removal has been confirmed. A fish-barrier waterfall near the YNP border will prevent existing Slough Creek rainbows and hybrids from penetrating the headwaters section of Buffalo Creek (and Hidden Lake at the creek’s headwaters), thus maintaining an isolated genetically pure population of Yellowstone cutts.
Opponents argue that the agencies should not be killing healthy and sporting populations of wild trout, that rotenone is a dangerous for the environment and humans, that humans shouldn’t interfere with natural selection, that it violates of the federal Wilderness Act of 1964, and more. FWP has responded to these concerns.
FWP and YNP have prioritized native fish populations in recent years, citing their “outstanding” and “immeasurable ecological, historical, and recreational value.”
The Yellowstone cutthroat trout’s range has been reduced by over 50 percent since European colonization, and its population is under continuous threat from several sources including predation from non-native fish, hybridization, and climate change. Yellowstone cutts are only found in the Yellowstone River drainage (unless you include the visually and geographically distinct population of cutthroat trout in the upper Snake River watershed, but that’s another article).
The project is a collaboration between FWP, the National Park Service, and the U.S. Forest Service, and is scheduled to take place through 2026.
Joshua Bergan is Fly Fisherman's digital editor.