Before the fur trade wiped out the majority of California\u2019s sea otters, thousands inhabited the west coast\u2019s largest estuary\u2014San Francisco Bay. Though the otters there went extinct by the mid-1800s, other populations managed to survive by taking refuge along the state\u2019s rugged coastline. In isolated pockets, those survivors found safe havens, says Tim Tinker, a wildlife biologist at the University of California, Santa Cruz. Hundreds of years later, conservationists helping the sea otters recover focused their efforts on where they found those remnant populations, overlooking the estuaries they once called home.<\/p>\n
\u201cThat unconscious bias has affected everything. It\u2019s affected where we do research and where we think otters will be,\u201d says Tinker. Now, those recovery efforts are being reevaluated.<\/p>\n
It is well known that otters perform an important role in coastal kelp forests by keeping herbivorous sea urchins in check<\/a>. According to a new study<\/a> coauthored by Tinker, they have an equally important job in estuaries. The finding suggests that reintroducing sea otters to estuaries could benefit those ecosystems.<\/p>\n Skeletal evidence unearthed by archaeologists beginning in the early 1900s had given scientists an inkling that sea otters once inhabited estuaries, but the connection was firmly established in the 1980s when the animals began living in Elkhorn Slough, a four-square-kilometer estuary that meanders inland from Monterey Bay. In the mid-1990s, conservationists at the Monterey Bay Aquarium began introducing rehabilitated otters to the area, helping the small population grow. By 2015, otters numbered more than 100.<\/p>\n Until recently, however, scientists considered Elkhorn Slough\u2019s burgeoning population something of an anomaly.<\/p>\n That changed in 2013, when Brent Hughes, a biologist at Sonoma State University in California, noticed the estuary\u2019s eelgrass, an endangered seagrass, was bouncing back from the brink of extinction. The otters, Hughes discovered, were causing a trophic cascade that benefited the eelgrass: by feasting on crabs, otters were preventing the crustaceans from overeating microorganisms that keep algae blooms at bay. Without these oxygen-depleting blooms, the seagrasses could recover. Three decades after the otters\u2019 return, the slough\u2019s eelgrass has increased sixfold.<\/p>\n \u201cThat was the aha moment,\u201d Hughes says. \u201cThat\u2019s when we realized, okay, these animals really should be in these estuaries.\u201d<\/p>\n In the new study, which Hughes led, the researchers imagined if the sea otter conservation success seen in Elkhorn Slough were transposed to other estuaries. San Francisco Bay, they found, could potentially support 6,000 otters\u2014more than double the population of sea otters currently ranging from California to British Columbia.<\/p>\n Some experts, however, have qualms about expanding recovery efforts to these ecosystems\u2014even if they do represent the sea otters\u2019 true historical range.<\/p>\n \u201cThe whole business of moving otters into estuaries is fairly controversial,\u201d says James Estes, an ecologist at the University of California, Santa Cruz, who was not involved in the study. There\u2019s a big difference between Elkhorn Slough and San Francisco Bay, he says.<\/p>\n The bay has changed dramatically since it last harbored otters more than a century ago, says Karl Mayer, the sea otter field response coordinator at Monterey Bay Aquarium. It\u2019s traversed daily by large tankers and commuter ferries, and lined by two crude oil refineries, making it more dangerous for sea otters.<\/p>\n Compounding those threats, old landfills leach heavy metals and DDT into the bay, which could be particularly dangerous for otters, Mayer adds. That\u2019s because shellfish, otters\u2019 primary food, are filter feeders that can absorb high concentrations of toxins from the water.<\/p>\n Because of their predilection for shellfish, sea otters could also disrupt shellfish harvesting. That might cause some hard feelings among local fishers, Mayer says. But even without help from humans, otters could make their way back to San Francisco Bay, he adds.<\/p>\n But Tinker says reintroduction is worth exploring\u2014to the bay and to estuaries all along California. \u201cIn the future, estuaries will play a major role in recovery. If you asked us 20 years ago, none of us would have said this.\u201d<\/p>\n Correction: A previous version of this article implied there was an active shellfish industry in San Francisco Bay.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":" Before the fur trade wiped out the majority of California\u2019s sea otters, thousands inhabited the west coast\u2019s largest estuary\u2014San Francisco Bay. Though the otters there went extinct by the mid-1800s, other populations managed to survive by taking refuge along the <\/p>\n