ANCHORAGE - A species of rare northern right whales has established residency near the Pribilof Islands for a third straight year.

As many as five of the mammals have been sighted feeding just east of the islands - sparking new hope for what is considered the most endangered population of large whales in the world.

"This appears to be their summer home," said Cynthia Tynan, a National Oceanic and Atmospheric Administration oceanographer at the Northwest Fisheries Science Center in Seattle.

Before the Pribilof sightings, northern right whales were believed to be so few in number that there was little that could be done on their behalf. But scientists now have a place to focus their research, including determining the whales' prey and the ocean conditions they prefer, Tynan said.

Right whales until recently were thought all but extinct in the North Pacific.

Biologists still don't know how many remain, but they may number fewer than 100, Tynan said. Fewer than 300 are thought to remain in the Atlantic Ocean.

But curiously, right whales are thriving in the southern hemisphere, said Doug DeMaster, director of NOAA's National Marine Mammal Laboratory in Seattle.

Rights are baleen whales similar in size and color to bowheads. They grow to 60 feet long and can weigh 60 tons. Individuals can be distinguished because of the wartlike growths called callosities that form in unique patterns around their mouths and eyes. Scientists don't know where they calve or spend the winters.

They were considered the "right" whale to hunt by Yankee commercial whalers in the Atlantic and Pacific oceans because they are slow swimmers and easy to approach and have thick blubber. They also float after being killed.

The whales have been a protected species since 1935. But the first hope for the whales in the North Pacific glimmered in 1996 when fisheries biologist Pam Goddard took a picture of a pod of rights from a research vessel.

Researchers back at the National Marine Mammal Laboratory in Seattle looked at the photos and found that she had the first confirmed sighting of a right-whale calf in the North Pacific in 150 years.

In 1997, Tynan found five to seven right whales in the Bering Sea. She photographed them and took tissue samples. The samples will help determine if the population is genetically distinct from other right whales.