India, Oct. 16 -- During summer mornings at Yellowstone Lake, workers in rubber boots and life jackets pull up gillnets in an effort to reverse years of ecological damage. By October, the seasonal fishing operation typically winds down after deploying thousands of miles of gillnets, according to the National Park Service (NPS). The target is an invasive fish first detected in the lake in 1994: lake trout.

The effects extended beyond the fishery. By the mid-to-late 2000s, the number of cutthroat trout spawning in streams had fallen to just 5% to 10% of late-1970s levels, according to the NPS. Anglers caught fewer fish, park rangers saw fewer animals around the lake, and some fishing guides reduced tours in affected areas. The decline thre...