YELLOWSTONE NATIONAL PARK, Wyo. (AP) — Parts of three rivers in Yellowstone National Park are closed to fishing because of unusually warm water temperatures.

Starting Wednesday, park officials are prohibiting fishing on the Gibbon River below Gibbon Falls, Firehole River below Keppler Cascades, and the Madison River.

Park officials say temperatures in the Gibbon River have been above 73 degrees for much of the past two weeks. The Firehole River has been above 78 degrees.

Such warm water can be stressful or even fatal for trout.

Yellowstone officials additional areas could also be closed to fishing if warm weather and low stream flows continue.