Study: State Sea Otter Population Could Boom If Relocated Into San Francisco Bay

ELKHORN SLOUGH (KPIX 5) -- Sea otter populations could boom in the San Francisco Bay if the otters were to get a boost from humans and were relocated into the bay waters, according to a new study led by marine biologist Brent Hughes at Sonoma State University.

"Putting them in SF bay could double, maybe triple the population," said Hughes. "Our predictions are that San Francisco Bay could potentially support around 6,000 sea otters on average."

Currently, there are roughly 3,000 sea otters statewide, concentrated along a 300 mile stretch of coastline from Point Conception near Santa Barbara to Half Moon Bay. The otters have been essentially boxed in by an even bigger predator.

"At both ends of the range in northern and southern California, there are attacks by great white sharks," said Hughes.

The otters spend the majority of their waking hours floating on their backs while feeding or grooming. So detecting a shark approaching from below or from the rear would be difficult, making the otters easy targets.

However, the otters are not a primary food source for the great whites and are often abandoned after the initial bite.

"It's not necessarily eaten by the great white shark, it's just attacked, let go, but that mortal wound ends up killing the sea otter, then they wash up on the shore," said Hughes.

In 2017, a beachgoer captured a sea otter pup on video as it came ashore in Carmel with several shark bite marks. Its mother was killed in the shark attack.

Hughes said otters are adaptable to a wide range of habitats, from freshwater to saltwater, and were once abundant in estuarine habitats all throughout the Bay Area before trappers hunted them to near extinction.

The sea otter study predicts that if humans were to intervene and repopulate the San Francisco Bay waters with a group of females and males, that in 20 to 30 years, the population would skyrocket, with the majority of the creatures clustering in Richardson Bay off the shores of Sausalito, Belvedere and Tiburon, and also towards San Pablo Bay off the shores of Richmond and San Pablo.

Hughes says the study is one more consideration in the management of the otter population, which has plateaued in recent years, as their current 300 mile range has reached capacity.

"It will likely be put on the table as a potential management objective, or possible strategy for enhancing the sea otter population," said Hughes.

"The San Francisco Bay a risky place for a sea otter to live. There's boat traffic, shipping lanes, the occasional oil spill, pollutants. All these factors need to be considered before humans relocate sea otters to an estuary like San Francisco," said Hughes, "But having more otters would add this extra insurance policy for sea otter conservation."