Nonnative Fish Species
Nonnative fish distribution and their influence on native fish are not static. While they have not been intentionally stocked since the 1930s, nonnative fish continue to advance into new habitats and hybridize with or displace native fish.
Hybridization of cutthroat trout resulting from rainbow trout range expansion continues to be the greatest threat to the park’s remaining native fish populations in waters outside the Yellowstone River headwaters, Yellowstone Lake, and the Snake River headwaters.
Not all of the movement by nonnative fish in Yellowstone has occurred naturally. Nonnative lake trout, intentionally introduced by managers in 1890 to Lewis and Shoshone lakes, and introduced (possibly intentionally) to Yellowstone Lake in the mid-1980s, first appeared in angler catches in 1994. The lake trout population expanded and, over the following decade, caused a rapid decline in the Yellowstone cutthroat trout population in Yellowstone Lake.
Lake trout prey on Yellowstone cutthroat trout.
Rainbow trout are native to North America in waters which drain to the Pacific Ocean from northern Mexico to Alaska.
Eastern Brook Trout
Eastern brook trout was the first nonnative species introduced in Yellowstone—stocked in the (then fishless) Firehole River in 1889.
The brown trout is the only nonnative fish species in Yellowstone that is not native to North America.
Native to the Missouri and Yellowstone river drainages in Montana and Wyoming, the lake chub is not native to Yellowstone National Park.
New Zealand Mud Snails
New Zealand mudsnails are invasive and have a significant detrimental effect on Yellowstone.
Whirling disease can infect some trout and salmon.
Red-rimmed melania, a small snail, was discovered in a warm swimming area.
Catch a Fish
Be a responsible angler and understand the regulations before you come.
Clean, Drain, and Dry
Protect park waters by preventing the spread of aquatic invasive species.
Learn about the park's abundant and diverse species—67 mammals, 330 birds, 16 fish, 5 amphibians, and 6 reptiles.
Last updated: June 15, 2020