Under the Sea — November 30, 2016 at 10:00 am

Welcome Back, Otter


Sea Otters British Columbia


Sea otters are adorable. They float on their back, eating urchins and crabs, and roll around in big furry rafts and kelp beds. And they’re coming back.

The Fall of the Otter

Sea otters once ranged the Pacific Coast from Baja to Alaska. But they were hunted for their thick fur: lacking blubber to keep them warm in the cold Northern Pacific, their fur is dense and thick. They were hunted for that fur by waves of Russian, American, British and Canadian fur trappers. By the 1880s they were nearly extinct. Only a few small populations remained in California and Alaska by the time they were protected by the Endangered Species Act in the 1970s. Small populations were reintroduced to Vancouver Island, British Columbia’s Central Coast, and the Olympic Peninsula.

Now otters are bouncing back. For the first time, the California otter count has risen above 3,500. And their presence is part of a web of ecological effects involving sea stars to urchins to seaweed to sharks.

Life Without Otters Isn’t Much of a Life

Sea otters are a keystone species, with a disproportionate effect on the ecosystem around them. Otters eat urchins, and they eat voraciously to fuel their fast metabolism that keeps them warm without blubber in the cold sea. Without otters, the sea urchins will eat kelp forests down to nothing. The denuded kelp forests mean lower fish populations that depend on the kelp forests. In Oregon, where there are no otters, kelp forests and fisheries are weaker than either in California or British Columbia’s ottery seas.

Trying to explain the current otter boom, researchers at the US Geological Survey noticed a few changes in the Pacific. One was the 2014-15 Sea Star Wasting Disease, caused by a densovirus. Sea stars are predators, and they also eat urchins, so the urchin population rose in the absence of the sea stars. Otters, with a larger than usual buffet of their favorite food, chowed down. Their population rose. The sea star population seemed to rebound well in 2016, so the urchin population may cycle down as well. A trend of minor adjustments will probably follow, what ecologists call dynamic equilibrium.

The Good News Keeps on Coming

But there’s a new factor at play. In 1994, California enacted gillnetting restrictions. Gillnets snared a lot of accidental bycatch, especially sharks. The shark population is rebounding too, and to a shark, an otter is a nice little snack—although they much prefer seals, sea lions and elephant seals, which pack calorie-rich blubber. The Pacific is slowly restoring a complete ecosystem with sea stars, urchins, otters, and Jaws as apex predator, so we can look forward to a healthier sea. We’re gonna need a bigger boat.

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