Yellowstone National Park is managed by the National Park Service. It has its own rules, regulations and requirements separate other National parks and from the surrounding states of Montana, Wyoming, and Idaho. You will need a Yellowstone Park Fishing License.
Yellowstone Park is home to two species of native cutthroat trout—the Yellowstone cutthroat trout and the westslope cutthroat trout. A third cutthroat, the Snake River fine-spotted cutthroat trout, is considered a subspecies of the Yellowstone cutthroat trout. The fish is covered with small spots over its body. These cutthroats are found in the Snake River drainage.
Few realize that park waters also host native Arctic grayling, as well as populations of non-native rainbow, brown, brook, and lake trout. Lake trout have established themselves in Yellowstone Lake, where they prey on native cutthroat populations. Efforts to remove lake trout from Yellowstone Lake have done some good and cutthroat populations are on the rebound.