Lake trout are bad news because they prey on cutthroat trout, one of just two native fish species in Yellowstone Lake. Cutthroats are a nutritional staple for 43 animal species, including the threatened grizzly bear. The cutthroat also supports a fishing industry valued at $36 million annually.
Anglers confirmed the existence of lake trout in 1994, but netting indicates that the species has been present much longer: Park staffers recently caught a 20-year-old female weighing 21 pounds. In contrast, cutthroat trout rarely exceed 4 pounds.
This summer, the Park Service has been probing for lake trout hot spots and experimenting with different kinds of nets. Large-scale gill-netting will begin next year, and may continue in perpetuity. On the advice of fish biologists, the park has given up its initial goal to eradicate the trout invaders. Now, officials say, they hope only to keep the invaders under control.