Yellowstone Cutthroat TroutThese Yellowstone cutthroats have swum up the Lamar River drainage to deposit their eggs in the gravel of a streambed. This spring and early summer spawning pilgrimage makes the fish vulnerable to predators like eagles, bears, and otters.Native Yellowstone cutthroats (Oncorhynchus clarkii bouvieri) have recently faced a new enemy in the form of invasive lake trout (Salvelinus namaycush), which are larger fish that prey on them.—Cathy Newman

Photograph by Jay Fleming

Pictures: Trout vs. Trout in Yellowstone Lake

Things were going swimmingly for Yellowstone cutthroats, a species of trout native to Wyoming’s Yellowstone Lake. Then someone added a few non-native lake trout to the mix.

January 24, 2013