Unalaska, AK – A very rare white killer whale has been seen in the Bering Sea near the Aleutian Islands.

The orca was spotted by a marine mammal observer from NOAA's National Marine Mammal Laboratory in Seattle, working onboard the National Oceanic and Atmospheric Administration vessel Oscar Dyson, which was conducting a survey in the Bering Sea last month.

John Durban, a biologist at the marine mammal lab, said the whale is apparently a male, and at least 20 years old.

"He doesn't appear to be a full albino, but he's certainly very white compared to a normal whale," he said. "But there appears to be very little wrong with him--he's fit and health, as far as we can tell."

The whale was part of a pod seen near Kanaga Volcano in the Aleutians. There are only two previously documented sightings of a white killer whale in Alaskan waters, one near the Aleutians and one in the northern Bering Sea. Holly Fearnbach, the observer on the NOAA ship, took several pictures of the whale's dorsal fin, and researchers are now comparing them to the photos from earlier sightings to try to determine if it's the same animal.

Durban said that having such an obviously different-looking whale swimming around the Bering Sea could be useful for researchers.

"He really serves as an interesting indicator animal for us to study the movement patterns of these whales," he said. "We'll know soon if it's the same one [seen previously], but there certainly aren't many out there that are white."

The Oscar Dyson is currently en route back to Kodiak, its home port. Durban said the research trip also yielded insights about the activities of killer whales in the Aleutians scientists previously thought that killer whales mostly visited here in the summer, but now it appears that some of them may live here year-round.