Eighteen species of fish live in Yellowstone, including the Yellowstone cutthroat trout. This fish is highly sought by anglers, and most of them live in Yellowstone. The Yellowstone cutthroat trout has faced several threats since the 1980s, including the suspected illegal introduction into Yellowstone Lake of lake trout, an invasive species which eat the smaller cutthroat trout. The cutthroat trout has also faced an ongoing drought, as well as the accidental introduction of a parasite—whirling disease—which kills younger fish. Since 2001, all native sport fish species caught in Yellowstone waterways are subject to a catch and release law.