SF Bay could help triple otter population
San Francisco Bay could act as a haven for California’s threatened southern sea otters and could potentially triple the existing population, according to a new study led by Sonoma State University.
Historical evidence including archaeological finds supports that the bay once hosted a large population of otters prior to the mid-19th century, the study states. While the bay and surrounding areas have undergone significant changes during the past 150 years, the study’s lead author, Brent Hughes, said their findings show otters could still flourish if reestablished.
“Just because of the massive size of San Francisco Bay and its existing habitat, it could still support a thriving sea otter population,” said Hughes, an assistant professor of biology at Sonoma State University. “However, there are a bunch of risks and we highlight that in the paper. So it’s not like you can throw sea otters into the bay right now and it wouldn’t be without any risk to the sea otter.”
The new study, published in “PeerJ: the Journal of Life and Environmental Sciences” in December, found that San Francisco Bay could support about 6,600 southern otters. Today, there are about 3,000 otters found in central and southern California waters. Other estuaries such as those in Drakes Estero, Tomales Bay, Bodega Bay and Humboldt Bay could provide further habitat, the study states.
Establishing a new population of otters has proven to be successful in some regions in the past, but also controversial. Otters can provide several ecological benefits to local estuaries and could help the restoration of eelgrass beds that are vital to marine animals and migratory birds, researchers say. But otters also eat substantial amounts of shellfish each day to sustain their weight and compete with fishermen for their catch.
“To maintain their core temperature, they have to eat 25% of their weight every day to stay alive,” Hughes said. “That’s a lot.”
Hog Island Oyster Co. vice president Terry Sawyer said from his experience handling otters while working with the Monterey Bay Aquarium, he knows they are persistent and strong enough to tear through the mesh bags that aquaculturists use to grow oysters and other shellfish in Tomales Bay.
“They’re fascinating, high-maintenance animals and they’re incredibly powerful,” he said. “And if they really want to get at something,
they’ll get it.”
Great white ‘gauntlet’
California’s and Baja California once had as many as 20,000 southern sea otter in the years before fur traders began methodically killing them for their valuable pelts beginning in the mid19th century.
Once thought extinct, a small group of otters survived
with their progeny making up the existing population. The otters are listed as a threatened species under the Endangered Species Act.
While an otter is occasionally spotted in and around San Francisco Bay, the bulk of the state’s population is located in waters south of Half Moon Bay or north in Washington and Alaska.