SAN JOSE, Calif. — Relocating sea otters to places in Northern California and Oregon where they haven’t lived for generations, including possibly using helicopter rides to move a few dozen from the Monterey Bay area into San Francisco Bay, is feasible and could help expand populations of the endangered marine mammals.
But there are sensitive economic issues that have to be worked out first, chief among them how it might affect commercial fishermen who catch species like Dungeness crab that sea otters also like to eat.
That was the conclusion this week from a new report from the U.S. Fish and Wildlife Service. The 200-page study, required by Congress, provided momentum to the growing idea among many marine biologists and environmentalists that the best way to help restore endangered sea otters is to spread their numbers out over a wider area across the West Coast.
“If we were to rely on natural range expansion it would be a very, very long time before sea otters were able to regain their historical range,” said Michele Zwartjes, co-author of the study and a field supervisor for the U.S. Fish and Wildlife Service in Oregon.
“We have recommended very small targeted reintroductions — maybe 100 or 200 sea otters in 30 years, not thousands,” she added. “We foresee that any impacts would be very localized for a very long period of time.”
Similar relocation efforts have happened with California condors over the past 30 years. Scientists have bred the endangered birds in zoos, then released them in Big Sur, the Grand Canyon and other locations, increasing condors’ numbers steadily.
But condors eat dead deer and dead sea lions. Otters eat living animals like Dungeness crab, a $51 million annual commercial fishery in California.
“They really need to think this through,” said Mike Conroy, executive director of the Pacific Coast Federation of Fishermen’s Associations in San Francisco. “These ecosystems have evolved without the presence of sea otters for 200 years. If this isn’t thought out, it could be disastrous.”
A jump in sea otter numbers in southern Alaska in recent decades led to drops in the catch of Dungeness crabs there. In Alaska, there are more than 90,000 otters. Along California’s Central coast, there are about 3,000.
The report does not give approval to relocating otters, most of which currently live in California between Santa Cruz and Morro Bay. More study would be needed, Fish and Wildlife Service officials said, to choose the best locations and learn exactly how otters would impact local fishing economies, including crab, clams, abalone and other shellfish.
Some areas that have been considered are San Francisco Bay, the Sonoma Coast and Drake’s Estero Lagoon in Marin County.
The idea is to expand otters’ genetic diversity and reduce the risk of one big event like an oil spill wiping out a large chunk of the sea otter population by moving small numbers so they can re-establish populations.
Historically there were about 16,000 sea otters along the entire California coast. But they were hunted relentlessly in the late 1700s and early 1800s by Russian, British and American fur traders for their pelts.
Many lived in San Francisco Bay. But by the Gold Rush, they were all but gone. They were feared extinct until the 1930s, when about 50 were discovered in remote Big Sur coves. Protected by the Endangered Species Act in 1977, they began a slow comeback.
Over the last decade, however, sea otters haven’t been able to expand north past the Pigeon Point area in San Mateo County because of attacks by great white sharks. Federal laws have protected elephant seals, sea lions and other marine mammals that the sharks eat. Also, climate change has warmed waters, and more juvenile great white sharks have moved north into the area from Southern California.
The goal is to get otters around the shark hot spot so they can re-establish farther up the Northern California coast, researchers say.
“We are seeing more shark bites than we have ever before,” said Aimee David, vice president for U.S. and California ocean conservation at the Monterey Bay Aquarium. “They are not the prey of sharks, but as more sharks come north because of changing temperature conditions in the ocean, these sharks mistake otters for prey, bite them and often the bites are fatal.”
The aquarium’s research has helped show that even though otters are known for living in kelp beds in the ocean, they can also thrive in bays and lagoons. Starting in 2001, aquarium scientists began taking young otters that had been separated from their mothers in the ocean, having captive female otters raise them, then releasing them into Elkhorn Slough in northern Monterey County.
At first there were 20 wild otters there. After releasing 37 “surrogate otters” over 15 years, the population in Elkhorn Slough jumped to between 100 and 150. That could happen in San Francisco Bay.
“San Francisco Bay could support a large number of sea otters, given its size and potential as habitat,” said Jessica Fujii, the aquarium’s sea otter program manager. “That doesn’t mean it is the best location, but it is an area to be considered.”
The U.S. Fish and Wildlife Service will begin hosting public meetings over the next year in coastal communities in Northern California and Oregon to discuss the issue with residents, Zwartjes said. If suitable locations are found, she said, the service would conduct a detailed economic study and a full environmental study before giving the green light.
“If we were to reintroduce sea otters, where could we do that with the greatest chance of biological success?” she said. “And how could we minimize any impacts on a local level to fisheries?”