By Yereth Rosen
ANCHORAGE, Alaska (Reuters) - Three apparently misguided killer whales are loitering far up an Alaska river and starting to show signs of stress after three weeks in fresh water, federal fisheries officials said on Thursday.
The three whales are about 30 miles up the Nushagak River in southwestern Alaska, after swimming upstream from Bristol Bay last month presumably in pursuit of food, and their continued presence there has confounded scientists.
"We don't know ... if they lost their way or why they're lingering around," said Julie Speegle, a spokewoman for the National Oceanic and Atmospheric Administration (NOAA).
Killer whales often swim around the mouth of that river, where it pours into saltwater, but have never been recorded staying so far upstream for so long in any Alaska river, she said.
The long stay outside of their natural habitat appears to be taking a toll on the whales, Speegle said.
"They have developed a filmy covering on their skin that is typical of marine mammals when they spend a lot of time in fresh water," she said. That filmy cover is an indicator of stress, she added.
Scientists from NOAA's National Marine Fisheries Service, along with state and local officials, are watching the whales to determine whether action is needed to shoo them back to saltwater, Speegle said.
The Nushagak River typically freezes over in late October or early November, so the whales need to leave the area soon. "But they just don't seem to be going anywhere," she said.
(Editing by Steve Gorman and Greg McCune)