1. Fisheries and Oceans Canada; Pacific Biological Station; 3190 Hammond Bay Road Nanaimo British Columbia V9T 6N7 Canada
2. Department of Biological Sciences; University of Alberta; Edmonton Alberta T6G 2E9 Canada
3. Department of Biology; Pennsylvania State University; University Park Pennsylvania 16802 USA
4. Fisheries and Oceans Canada; Institute of Ocean Sciences; 9860 West Saanich Road Sidney British Columbia V8L 5T5 Canada