MONTEREY (CBS/AP) — New data show a slight increase in the number of threatened California sea otters swimming in coastal waters, a comeback made more difficult because of a recent uptick in shark attacks.

The U.S. Geological Survey on Tuesday said the sea otter population—a group nearly wiped out by fur traders about a century ago—has increased 1.5 percent since 2010.

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USGS said there are now 2,792 sea otters in California waters, compared with 2,711 in 2010.

Marine scientists said shark attacks have slowed the otters’ recovery, with 335 of the furry critters found dead from bites in 2011.

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The uptick in shark attacks has vexed researchers; sharks do not eat otters.

In 2011 sharks accounted for 30 percent of otter deaths, up from eight percent in the 1980s.

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