1. Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Santa Cruz, CA 95060
2. Department of Applied Mathematics, University of California, Santa Cruz, CA 95060
3. Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697
4. Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
5. Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich 8057, Switzerland