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Killer whales' swim into Alaska freshwater river concerns biologists

Three killer whales discovered in freshwater far up Southwest Alaska's Nushagak River have state and federal biologists considering options to intervene and move them back to the ocean.

The two adult whales and one juvenile were spotted three weeks ago on the Nushagak and have been lingering about 30 miles up the river from Dillingham, near a fork south of the village of Ekwok, according to the National Oceanic and Atmospheric Administration. Local residents say the whales are about an hour's boat ride upriver from where the river's freshwater mixes with Nushgak Bay's saltwater.

While residents have seen killer whales at the river's mouth before, it's the first documented case of killer whales traveling this far up the Nushagak, NOAA says. It's also the first report in Alaska of killer whales staying for prolonged periods of time in a freshwater river, NOAA Alaska fisheries spokeswoman Julie Speegle said.

It's unclear why the whales swam so far upriver. And they aren't showing any signs of leaving, Speegle said. Federal and state biologists are watching the whales' condition to see if they should step in to help, she said.

"They have developed a sort of filmy covering that is typical for marine mammals to develop in freshwater," Speegle said. "It's an indication of freshwater stress."

Another cause for concern: cooling temperatures, said Barbara Mahoney, a biologist with NOAA's National Marine Fisheries Service.

As winter approaches, melting of snow and glaciers slows in the mountains that feed the Nushagak, causing the river to drop, Mahoney said. Mahoney had heard reports of the river dropping, and a shallower river would mean more difficult passage for the whales, she said. The river usually freezes over by late October or early November, she said.

"We are coming up against some natural, weather-related time lines," Mahoney said.

Alaska killer whale expert Craig Matkin said the whales of this type -- so-called transient killer whales, which feed on other marine mammals as opposed to fish -- don't appear to be suffering from starvation. But Matkin said he's not sure what they could be feeding on that far up the river.

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