For the second time in seven years Yellowstone staff are working to remove nonnative Brook trout from Soda Butte Creek to protect native Yellowstone cutthroat trout (above, during spawning)/NPS file, Jay Fleming

Seven years after nonnative brook trout were removed from Soda Butte Creek in the northeastern corner of Yellowstone National Park, the fish again have been spotted in the creek.

Park staff announced Wednesday that they, along with Montana, Fish, Wildlife & Parks and Custer Gallatin National Forest, will begin work August 14 to again remove the brook trout so they won't overrun the native Yellowstone cutthroat trout and "eventually invade the entire Lamar River watershed, threatening the largest remaining riverine population of Yellowstone cutthroat trout in existence."

Soda Butte Creek closure map/NPS

Back in 2016 crews worked to treat streams and tributaries in the Soda Butte Creek drainage, from its headwaters in the Beartooth Mountains downstream to Icebox Canyon, approximately 10 miles from its confluence with the Lamar River, to remove brook trout. Park staff has no idea how the fish got back into the creek.

From August 14-18, Soda Butte Creek will be closed to the public from the park boundary at the Northeast Entrance to Ice Box Canyon while biologists remove brook trout by applying an EPA-approved piscicide (rotenone). Warm Creek and Soda Butte Creek picnic areas will also be closed for project staging. View a map for details. 

Cutthroat trout will be moved out of the treatment area next week by electroshocking. The salvaged cutthroat trout will be held in the Soda Butte Creek watershed in upper untreated tributaries, then released back into Soda Butte Creek once fisheries staff complete the treatment.  

Cutthroat trout are the only trout species native to the park. They are the most ecologically important fish of the Greater Yellowstone Ecosystem and are highly regarded by anglers. Genetically pure Yellowstone cutthroat trout populations have declined throughout their natural range in the Intermountain West, succumbing to competition with and predation by nonnative fish species, a loss of genetic integrity through hybridization, habitat degradation and predation.

The cutthroats are relatively easy to identify: They have a red slash along jaw and spots common to all cutthroat varieties, their bodies are mostly yellow-brown with darker olive or gray hues on the back, lighter yellow on sides, and they have a highly variable black spotting pattern, but few to no spots on the head.

Nonnative Brook trout arrived in Yellowstone in 1889 to stock the fishless Fall River/NPS file, Jay Fleming