Cutthroat trout, a native species in trouble around the West, are facing an increasing threat in a key sanctuary, Yellowstone National Park. Whirling disease, spread by a European parasite that showed up in the park five years ago, now infects 12 to 20 percent of the cutthroats in Yellowstone Lake, according to biologists’ studies. And in Pelican Creek, an important lake tributary and spawning area, the cutthroat population has crashed. Tens of thousands of cutthroats migrated up the creek to spawn each spring in the early 1980s, but only a few were spotted last spring, and the infection rate in some tests surpassed 90 percent.
Pelican Creek has suffered "a total
loss," says Todd Koel, a park biologist. "Here we are, in this
pristine environment, watching the proliferation of an exotic
(parasite). It’s sad."
Whirling disease damages
cartilage and nerves in trout and salmon, and can kill young fish
directly or by causing them to spin in the water, making them easy
prey for predators. Hundreds of streams around the West have been
infected (HCN, 9/18/95: The West's fisheries spin out of control,
by Ray Ring).
The disease adds to the pressure that
Yellowstone cutthroats feel from another predator: illegally
introduced lake trout. The fish’s decline could strain the
park’s ecosystem, because birds, bears and other animals have
evolved to feed on cutthroats. Biologists are carrying on a
campaign to thin the lake trout, and they’re advising anglers
and other people to be more careful: The whirling disease parasite
can be spread through muddy clothing and gear.