The Park Service pulled 7,000 trout from Yellowstone Lake this year. The fish are lake trout - an exotic first found here four years ago - that scientists blame for ravaging native Yellowstone cutthroat trout.
Some of these exotic
fish are more than 20 years old, and Park Service biologist Dan
Mahoney says the fish have probably been lurking in the lake's deep
waters all the while, even though they are a relatively recent
discovery. Until recently, the lake had remained the last major
stronghold for Yellowstone cutthroats, a species the U.S. Fish and
Wildlife Service is considering for protection under the Endangered
Species Act. Yet now, in tributary streams feeding one particular
area of the lake called the West Thumb, cutthroat trout numbers are
less than one-tenth of what they were in the
"Cutthroats are having a very hard time
all over. Lake trout are just one more threat to their future,"
says Rob Ament of American Wildlands in Bozeman,
The native Yellowstone cutthroat spawn in
streams and linger in shallows, where grizzly bears, raptors and
other wildlife can catch and feast on them. Lake trout, by
contrast, spend much of their lives in deeper waters, where they
remain inaccessible to the native diners that have long depended on
the cutthroat. They also are voracious predators: one lake trout
could eat an estimated 6,000 cutthroat in its lifetime.