Gallatin River
The westslope cutthroat trout "(Oncorhynchus clarki lewisi)" was widely distributed in the Gallatin River and Madison River drainages when the park was created. Genetically pure populations of subspecies today are restricted to two drainages. Last Chance creek in the Gallatin River drainage contains an aboriginal population. The Oxbow/Geode stream complex creek in the Yellowstone River drainage contain a genetically pure, but not native population as a result of stocking done in 1922. The introduction of brown, rainbow and brook trout into its original ranges essentially extirpated the subspecies from park waters. The National Park Service has an extensive program aimed at reestablishing this subspecies within suitable waters in the park. In 2014 after poisoning out rainbow trout in the Goose Lake chain in the Midway Geyser Basin, park officials established a westslope cutthroat trout broodstock in Goose Lake.