1. National Park Service, Yellowstone National Park, Fisheries and Aquatic Sciences Program, Post Office Box 168, Yellowstone National Park, Wyoming 82190, USA
2. Ecology Department, Fish and Wildlife Ecology and Management Program, Montana State University, Post Office Box 173460, Bozeman, Montana 59717, USA
3. U.S. Geological Survey, Northern Rocky Mountain Science Center, 2327 University Way, Bozeman, Montana 59715, USA
4. Wyoming Game and Fish Department, 2820 State Highway 120, Cody, Wyoming 82414, USA