Sea Otters Rebound in Southeast Alaska
STORY: Glacier Bay National Park lies at the northernmost tip of Southeast Alaska. The three-million-acre marine park is home to killer whales, eagles, and some of the world's largest glaciers.
Glacier Bay is also the latest place to be reclaimed by sea otters, which were hunted to extinction in Southeast Alaska 150 years ago by Russian fur traders. Their recovery began in the 1960s when biologists transplanted 400 sea otters from elsewhere in Alaska to Southeast. For two decades, the sea otter population remained steady. All that changed in the 1980s, says Brendan Kelly, a marine mammal scientist at the University of Alaska Fairbanks.
KELLY: "I've looked at the growth rates and they are above 20 percent per year, which we've seen other otter populations do elsewhere during their recolonization phase. Once they get their flippers under them and figure out how to exploit new habitat, they can grow that fast."
Sea otters are loved by tourists and others because they are incredibly cute. They float lazily on their backs, preening their fur and caring for their young. But beneath that cuddly fur coat lurks an insatiable appetite for crab, abalone, sea urchins and other marine life.
Dungeness crabs are one of the sea otter's favorite foods. Southeast Alaska once teamed with Dungeness and other crab species. But as sea otters continue to multiply and expand over their former range, crab populations are being hit especially hard, says Jim Taggart, a crab biologist studying Glacier Bay's ecosystem for the U.S. Geological Survey.
TAGGART: "We have every reason to believe that if the otter population continues to expand into Glacier Bay, it will have a very large impact on the crab population. We would expect the number of crabs to decline dramatically."
Tom Shirley is a University of Alaska Fairbanks biologist studying the interactions between crabs, sea otters and commercial fishermen in the bay. He says sea otters can wreak havoc on crab stocks.
SHIRLEY: "One study done in Prince William Sound found that a sea otter could eat 14 adult Dungeness crabs per day. The population of sea otters could eat the entire commercial catch of Dungeness crabs in Southeast Alaska in less than two weeks."
Much of the reason for the otter's tremendous appetite lies in the fact that they don't have a layer of fat to keep them warm in the frigid ocean. To stay warm, they must constantly burn energy. And to do that, they need lots of food.
Scientists agree that in the next few years, the rapidly growing sea otter population will reduce crab numbers to a level that probably existed just before the Russians arrived. Tom Shirley says other changes are in store for Southeast's ecosystem as well.
SHIRLEY: "We'll have lots of changes here. The otters feed on Dungeness crabs, king crabs and tanner crabs in shallow water. They also eat lots of sea urchins, and urchins eat macro algae. So if you remove the urchins, well, that means the kelp will increase in density. The kelp serves as habitat for a lot of fish, particularly the early life history stages of many species of fish. So it's going to change our fish populations. It will change the kelp, and a lot of other things."
Declining crab stocks in Glacier Bay National Park likely won't sit well with fishermen. Commercial crab fishermen are trying to stop Park Service from closing the park to fishing. Biologist Brendan Kelley says that if the Park Service fails in its efforts, sea otters themselves will ensure that fishermen go elsewhere.
KELLY: "I think one of the ironies of the whole Glacier Bay (fishing) debate is that it's just a matter of time before the otters put fishermen out of business anyway."
OUTRO: From the Sea Grant Program at the University of Alaska Fairbanks, this is Doug Schneider with Arctic Science Journeys.
Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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