Three killer whales have made an unprecedented trek into a fresh water river in southwest Alaska, a rare move for the saltwater mammals, federal officials said Thursday.
Barbara Mahoney, a biologist with the National Marine Fisheries Service in Anchorage, said it was the first time that the National Oceanic and Atmospheric Administration has received a report of killer whales being in fresh water in the state.
The whales, also known as orcas, swam about 30 miles up the Nushagak River to a spot just downriver from the village of Ekwok. The village is about 285 miles southwest of Anchorage.
The whales appeared to have been in the area for about three weeks and were last reported below the split of the east and west channel of the Nushagak. They were first reported by Anchorage television station KTUU.
Julie Speegle, a NOAA Fisheries spokeswoman for the Alaska region, said there have been reports of killer whales at the mouth of the Nushagak during the fall but this was different. "This is the first time they have been up this far on the river and the longest they have stayed," she said.
The whales are covered with a membrane that has been seen on marine mammals that remain in fresh water, she said, and they appeared to be stressed from being in fresh water.
Officials did not know why the whales were so far upriver.
"The only thing that I can assume is that they might be following the food. There might be some rich masses of silver salmon up that way," said Helen Aderman, marine mammal coordinator for the Bristol Bay Native Association in Dillingham.
Aderman said that as a girl growing up near another river in the region, beluga whales and harbor seals occasionally would swim 25 miles up the river to her home.
"You really have some unusual occurrences now and then," she said.
NOAA was taking a "wait-and-see" approach in hopes that the whales would leave the river on their own, Speegle said.
NOAA Fisheries biologists, the Alaska Department of Fish and Game and the U.S. Fish and Wildlife Service were monitoring the situation and consulting with experts. NOAA encouraged the public to stay at least 100 yards away from the whales to prevent any further stress.