Study Finds Eco-Crisis as Otters Decline

Killer whales that normally hunt seals and sea lions are now feeding on sea otters and creating an ecological crisis along the entire Aleutian Island chain of western Alaska, researchers say.

The sudden loss of thousands of sea otters is allowing a boom in the population of sea urchins and those animals, in turn, are stripping the undersea kelp forest, laying bare vast areas that once were lush with the marine plant.

The whole coastal ecosystem in western Alaska is now affected, says James Estes, a marine ecologist with the U.S. Geological Survey and UC Santa Cruz.

“Coastal fish, mussels, marine birds and other predators in the system could all be impacted. . . . The kelp beds serve as a nursery for small fish and other animals,” Estes said. “A lot of species depend on the kelp beds for their survival.”

He is co-author of a study appearing today in the journal Science.

Undersea beds of kelp, a sea plant that towers from the ocean floor and can grow in dense groves, have been reduced by 90% in some areas.

“The otters are down about 90% in the areas that we studied, while the sea urchins have increased by about tenfold,” Estes said.

Estes said that starting in the late 1980s, the sea lion and seal population crashed and is now about 10% of normal.

Deprived of their normal food, killer whales turned to the otter.

Estes said he and his colleagues estimate that a single killer whale will have to eat 1,825 otters a year to get its required nourishment.

Estes said there is no clear explanation for the decline in sea lions and seals, but some researchers believe those animals experienced a population crash because they could not get enough high-nutrition fish, their normal food. Overfishing has severely reduced the population of some fish species, he said.