1. Department of Fisheries and Wildlife, Oregon State University and Amnis Opes Institute, 200 SW 35th Street, Corvallis, Oregon 97333 USA and Programa de Pós-Graduação em Ecologia, Conservação e Manejo de Vida Silvestre, Departmento Biologia Geral, Universidade Federal de Minas Gerais, CP. 486, CEP. 30.161-970, Belo Horizonte, Minas Gerais, Brasil
2. Office of Research and Development, National Health and Environmental Effects Research Laboratory, Western Ecology Division, US Environmental Protection Agency, 200 SW 35th Street, Corvallis, Oregon 97333 USA