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Invasive green crabs threaten West Coast ecosystems. One solution? Otters

By Manuela López Restrepo

Published January 15, 2025 at 12:50 PM CST

He's never had to spend $20 on a salad and that is why he knows true peace.

As invasive green crabs wreak havoc on California's estuaries, a new study has found that a restored sea otter population might be the solution.

3 things to know

Green crabs, native to coastal Europe and North Africa, can be extremely destructive as an invasive species. They can damage oyster and seagrass beds and also consume small mudflat invertebrates that provide food for shorebirds.
As it turns out, sea otters — which are listed as threatened under the Endangered Species Act — love to eat these crabs. One estimate by researchers in California found that a single otter can consume somewhere between 50,000-120,000 crabs a year.
A new study, published in the Biological Invasions journal, found that there was a direct relationship between the two species: if an area had a healthy population of sea otters, it would also have a low green crab population.

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Can things really be this good?

Yes, says ecologist Rikke Jeppesen, whose team at Elkhorn Slough Reserve on the California coast published the recent study.

"It's really a win-win scenario if we can support a native threatened species, the sea otter, which in turn then helps control an invasive invertebrate," Jeppesen told All Things Considered. "So in other words, you can say that sea otters are our assistant managers of the estuary for invasive species control."

What's more, they're biologically predisposed to eating a lot of crabs, she said.

"Sea otters rely on fur for insulation as opposed to seals, which rely on blubber. Blubber insulates much better, so sea otters have to eat a lot to keep warm," she said. "It's basically a weasel in the water. And weasels are super active. They have a high metabolism. So to sustain sea otter health and keep warm, they just need to eat a lot."

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