The West Coast has been plagued by an invasive crab species for decades—but scientists now say a native resident is helping to remedy the issue, at least in one California ecosystem. That helper is an "adorable, fluffy, and hungry friend," per USA Today—the resident southern sea otter, which has seen a population boost in recent years at the Elkhorn Slough National Estuarine Research Reserve in Watsonville. "The otters are ... just [a] super voracious predator," says the reserve's Kerstin Wasson, co-author of a new study published in the Biological Invasions journal. "We calculated that the current otter population here eats somewhere between 50,000 and 120,000 green crabs a year."
To better create and implement "effective conservation strategies," the researchers decided to study how the sea otter's surging presence affected the reserve's waterways in terms of the pesky tiny green crabs that have infiltrated. This species of crab, originally from Europe, arrived on the West Coast sometime in the '80s and immediately got to work chowing down on all the local seagrass, as well as on baby crabs and salmon in the area. States up and down the Pacific coast, from California to Alaska, began erecting plans to find and get rid of the green crabs—all while the scientists at the Elkhorn reserve started seeing a slow return of threatened sea otters to the area, with today's population there now numbering about 120.
Study co-author Rikke Jeppesen says when she would first set traps for the green crabs in the early aughts, she'd sometimes catch up to 100 crabs in one trap, per the Washington Post. Once male and female sea otters arrived in droves at the Elkhorn estuary—some from the Monterey Bay Aquarium—that led to a noticeable reduction in the number of green crabs. "When we set the traps in the same place today, we'll get under 10 and often not even five," Jeppesen tells USA Today. "The sea otters, they're like an assistant manager for us." (More discoveries stories.)
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