Species recovery and recolonization of past habitats: lessons for science and conservation from sea otters in estuaries
Brent B. Hughes,
Kerstin Wasson,
M. Tim Tinker,
Susan L. Williams,
Lilian P. Carswell,
Katharyn E. Boyer,
Michael W. Beck,
Ron Eby,
Robert Scoles,
Michelle Staedler,
Sarah Espinosa,
Margot Hessing-Lewis,
Erin U. Foster,
Kathryn M. Beheshti,
Tracy M. Grimes,
Benjamin H. Becker,
Lisa Needles,
Joseph A. Tomoleoni,
Jane Rudebusch,
Ellen Hines,
Brian R. Silliman
Affiliations
Brent B. Hughes
Department of Biology, Sonoma State University, Rohnert Park, CA, USA
Kerstin Wasson
Elkhorn Slough National Estuarine Research Reserve, Watsonville, CA, USA
M. Tim Tinker
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, USA
Susan L. Williams
Department of Evolution and Ecology, Bodega Marine Laboratory, University of California, Davis, Bodega Bay, CA, USA
Lilian P. Carswell
Ventura Fish and Wildlife Office, United States Fish and Wildlife Service, Ventura, CA, USA
Katharyn E. Boyer
Estuary & Ocean Science Center, Department of Biology, San Francisco State University, Tiburon, CA, USA
Michael W. Beck
Institute of Marine Sciences, University of California, Santa Cruz, Santa Cruz, CA, USA
Ron Eby
Elkhorn Slough National Estuarine Research Reserve, Watsonville, CA, USA
Robert Scoles
Elkhorn Slough National Estuarine Research Reserve, Watsonville, CA, USA
Michelle Staedler
Monterey Bay Aquarium, Monterey, CA, USA
Sarah Espinosa
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, USA
Margot Hessing-Lewis
Hakai Institute, Heriot Bay, BC, Canada
Erin U. Foster
Hakai Institute, Heriot Bay, BC, Canada
Kathryn M. Beheshti
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, USA
Tracy M. Grimes
Department of Biology, San Diego State University, San Diego, CA, USA
Benjamin H. Becker
Point Reyes National Seashore, United States National Park Service, Point Reyes Station, CA, USA
Lisa Needles
Center for Coastal Marine Sciences, Department of Biological Sciences, California Polytechnic State University—San Luis Obispo, San Luis Obispo, CA, USA
Joseph A. Tomoleoni
U. S. Geological Survey, Western Ecological Research Center, Santa Cruz, CA, USA
Jane Rudebusch
Estuary & Ocean Science Center, Department of Geography and Environment, San Francisco State University, Tiburon, CA, USA
Ellen Hines
Estuary & Ocean Science Center, Department of Geography and Environment, San Francisco State University, Tiburon, CA, USA
Brian R. Silliman
Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University, Beaufort, NC, USA
Recovering species are often limited to much smaller areas than they historically occupied. Conservation planning for the recovering species is often based on this limited range, which may simply be an artifact of where the surviving population persisted. Southern sea otters (Enhydra lutris nereis) were hunted nearly to extinction but recovered from a small remnant population on a remote stretch of the California outer coast, where most of their recovery has occurred. However, studies of recently-recolonized estuaries have revealed that estuaries can provide southern sea otters with high quality habitats featuring shallow waters, high production and ample food, limited predators, and protected haul-out opportunities. Moreover, sea otters can have strong effects on estuarine ecosystems, fostering seagrass resilience through their consumption of invertebrate prey. Using a combination of literature reviews, population modeling, and prey surveys we explored the former estuarine habitats outside the current southern sea otter range to determine if these estuarine habitats can support healthy sea otter populations. We found the majority of studies and conservation efforts have focused on populations in exposed, rocky coastal habitats. Yet historical evidence indicates that sea otters were also formerly ubiquitous in estuaries. Our habitat-specific population growth model for California’s largest estuary—San Francisco Bay—determined that it alone can support about 6,600 sea otters, more than double the 2018 California population. Prey surveys in estuaries currently with (Elkhorn Slough and Morro Bay) and without (San Francisco Bay and Drakes Estero) sea otters indicated that the availability of prey, especially crabs, is sufficient to support healthy sea otter populations. Combining historical evidence with our results, we show that conservation practitioners could consider former estuarine habitats as targets for sea otter and ecosystem restoration. This study reveals the importance of understanding how recovering species interact with all the ecosystems they historically occupied, both for improved conservation of the recovering species and for successful restoration of ecosystem functions and processes.
