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Can Sea Otters Make a Comeback in the San Francisco Bay?

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A sea otter swims in Monterey Bay, California. Image Credit: Tania Larson/USGS

A sea otter swims in Monterey Bay, California.
Image Credit: Tania Larson/USGS

Imagine sea otters drifting and diving in San Francisco Bay and swimming in the abundant pickleweed of the salt marshes surrounding its waters.  Up until the early-1800s, that would have been a common sight. They’ve been long gone in our area, since the 1840s when fur hunters trapped the last of the surviving bay population around Corte Madera Creek.  A remnant population, discovered near Big Sur in 1938, has been slowly expanding from an estimated 50 otters.  Southern sea otter populations span from east of northern Santa Barbara to around Pigeon Point, and includes a small population on San Nicolas — the westernmost of the Channel Islands.

Sea otter range map. Image courtesy of Friends of the Sea Otter

Sea otter range map. Image courtesy of Friends of the Sea Otter

The annual Southern sea otter population count, just released, showed a complex but hopeful trend.  The population appears to be increasing slightly overall, but it still hovers below the level needed to delist the federally threatened species.  The southernmost population appears to have the highest mortality from great white shark bites.  They’re not eating them, just tasting, but the otters can’t survive a bite.

The largest population, in Elkhorn Slough on Monterey Bay, is the object of a new study by UC Santa Cruz professor Tim Tinker of the U.S. Geological Survey (USGS) and a team of scientists from a collaboration of agencies and non-profit organizations.

Dr. Tinker commented, “Otters are an important species to study.  They’re an apex predator and have a direct bearing on the health of the ecosystem.”  The preliminary data from the Elkhorn Slough otter study reveals some interesting information.

Tinker stated, “In the the slough, otters’ primary foods are crabs, clams and worms, as well as snails and other benthic species.  The data so far noted that areas in the slough populated by otters had healthier seagrass beds. Since with fewer crabs, the isopods and sea slugs could graze the algae off the grass, promoting better seagrass growth.”

I wondered about otter behavior in the slough compared to kelp beds.  He said instead of anchoring themselves and their pups to the kelp, otters in the slough use pickleweed or float in secluded, sheltered channels of the marsh.

“Sea otters,” he added, “also act as an indicator species, a watery “canary in a coalmine” for environmental toxins that might affect human health.  We eat many of the same sea creatures as otters, so toxins in their food may also be present in ours.”  Watch this video about an environmental contaminant that was killing sea otters that started at Pinto Lake in Monterey.

Veterinarians from the Monterey Bay Aquarium and the California Department of Fish and Wildlife examine a sedated wild sea otter, performing important health checkups and taking biopsies to study on this threatened species.Image Credit: Ben Young Landis/USGS

Veterinarians from the Monterey Bay Aquarium and the California Department of Fish and Wildlife examine a sedated wild sea otter, performing important health checkups and taking biopsies to study on this threatened species.
Image Credit: Ben Young Landis/USGS

The Elkhorn Slough study will track individual otters over the next couple of years to gain a more complete and deeper understanding of the estuarine population.  Scientists use dip nets to capture sea otters along with other methods.  Here’s a video of the scientists capturing an otter at Elkhorn Slough on Sept. 19, 2013  (courtesy of CA Department of Fish & Wildlife). Perhaps this will ultimately help scientists understand and better inform resource managers about how to bring the sea otters back to their historic range, which might eventually mean we could enjoy them again in our own estuary: the San Francisco Bay.

You can learn more about how you can help sea otters at the Friends of the Sea Otters website.  Test your otter counting skills on the USGS website for educators with the “Otter Spotter” game.  You can also enjoy the newly launched otter camera (during daytime hours) and observe otters at rest and play in Elkhorn Slough.  Many of them are females and pups.  Mostly, though, you can help sea otters by appreciating and protecting the amazing natural environments and land-sea interfaces we share.

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Category: Biology

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About the Author ()

Sharol Nelson-Embry is the Supervising Naturalist at the Crab Cove Visitor Center & Aquarium on San Francisco Bay in Alameda. Crab Cove is part of the East Bay Regional Park District, one of the largest and oldest regional park agencies in the nation. She graduated from Cal Poly, San Luis Obispo with a degree in Natural Resources Management and an epiphany that connecting kids with nature was her destiny. She's been rooted in the Bay Area since 1991 after working at nature centers and outdoor science schools around our fair state. She loves the great variety of habitats stretching from the Bay shoreline to the redwoods, lakes, and hills. Sharol enjoys connecting people to nature with articles in local newspapers and online forums. Read her previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.
  • 123tl78

    I hope they can. The world needs more sea otters.

  • Ron Eby

    It would be incredible if otters would actually recolonize San Francisco Bay. Historically this estuary had more otters than currently exist in their entire range. That was before so much of the bay was filled in for development, but major restoration efforts are significantly increasing the available wetlands. It may take many years before they run out of food here in Elkhorn Slough and search for new areas. Then they have to get around all the sharks at Ano Nuevo that feed on all the pinnipeds (especially elephant seals).

  • Gabe Heiss

    uhhhh, I lived in San Jose in 1999 and I am 95% sure that I saw sea otters floating in the kelp around Yerba Buena/Treasure Island off the Bay Bridge between San Francisco and Oakland. We were looking down a cliff and they were quite small, but what else could the be?! I am a mustelidae enthusiast, owning 2 ferrets up to that point, and several more plus 2 mink and a skunk since 2000.