1. US Environmental Protection Agency, National Center for Environmental Assessment, 26 W. Martin Luther King Dr., Cincinnati, Ohio 45268 USA
2. Department of Zoology, Michigan State University, East Lansing, Michigan 48824 USA
3. Environmental Sciences and Resources, Portland State University, Portland, Oregon 97207 USA
4. Department of Fisheries and Wildlife, Oregon State University, c/o US Environmental Protection Agency, 200 SW 35th Street, Corvallis, Oregon 97333 USA
5. US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, 200 SW 35th Street, Corvallis, Oregon 97333 USA
6. OAO Corporation, c/o US Environmental Protection Agency, 200 SW 35th Street, Corvallis, Oregon 97333 USA