ANCHORAGE (AP) -- Federal researchers said Thursday that the Aleutian Island sea otter population has dropped 70 percent this decade, largely because of predation by killer whales.
Based on a survey last spring, the U.S. Fish and Wildlife Service estimates that about 6,000 sea otters now populate the Aleutians, once home to the world's largest concentration of otters.
That number is down from about 19,000 in 1992 and as many as 100,000 in the 1980s, the agency said.
''We expected a decline,'' said Angela Doroff, Fish and Wildlife's sea otter program biologist. ''We hoped it wasn't going to be that bad.''
Doroff said the central Aleutians population was particularly diminished, though the aerial survey showed sharp declines throughout the chain.
Depleted or even endangered status could be sought for the animals, which she said would provide funding for monitoring and to come up with ways to mitigate the decline.
Killer whales, also known as orcas, are the prime suspect in the drop in adult otters.
Doroff said Fish and Wildlife can't yet account for why orcas might take a greater dietary interest in otters. The whales commonly eat Steller sea lions and harbor seals, both of which are also in significant decline in western Alaska.
''It could be a function of switching to different prey out of desperation,'' she said.
She said researchers were also looking at contamination as a possible contributing factor.
Fish and Wildlife is also concerned about otter stocks along the Alaska Peninsula and in the Kodiak Island region. It plans to expand its survey efforts in those regions.
This summer Russian biologists are scheduled to survey sea otter populations in the Commander Islands, a continuation of the Aleutian archipelago. Doroff said her agency is looking forward to seeing those results.
Natives in the Aleutians harvest some otters for subsistence use, but Fish and Wildlife said the levels are too low to have a significant on populations.
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