1. Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon 97331, USA
2. Department of Fish and Wildlife Sciences, University of Idaho, Moscow, Idaho 83844-1136, USA
3. Department of Microbiology, Oregon State University, 204 Nash Hall, Corvallis, Oregon 97331, USA
4. U.S. Geological Survey, Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon 97331, USA