1. Long Marine Laboratory, Institute of Marine Sciences, University of California Santa Cruz, 115 McAllister Way, Santa Cruz, California 95060, USA
2. Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, California 95060, USA
3. Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, Washington 98115, USA
4. Wildlife Conservation Society Canada, Whitehorse YT Y1A 0E9, Canada