ANCHORAGE (AP) -- They were thought the rarest whales in the world, virtually extinct across their former range in the North Pacific Ocean.
Yet as oceanographer Cynthia Tynan and others motored in a skiff across a glassy Bering Sea on a summer evening four years ago, they were amazed to find five and possibly seven northern right whales swimming near one another.
It was the largest group seen in half a century, and they had a lesson to teach.
''It's a day that stood out strong and clear in my mind and always will,'' Tynan said last week. ''It was a wonderful experience.''
The uncharacteristically calm sea allowed the scientists to take tissue samples with a crossbow and confirm that the whales were foraging about 300 miles from former summering grounds farther out on the Aleutian Chain. Attracted by a teeming bloom of tiny, fat-laden crustaceans, the animals had surfaced in shallower and warmer water east of the Pribilof Islands, in pursuit of an unexpected prey.
But right whales have an uncanny knack for finding rich concentrations of copepods across vast stretches of ocean, Tynan said, making them a sort of ''bellwether'' for changes in the marine ecosystem.
''They do it much better than we're able to as oceanographers,'' she said. ''They can tell us a lot when we can find them.''
Over the past five years, small groups of the planet's most endangered cetaceans have returned each July to the same southeastern Bering Sea waters just outside Bristol Bay, raising the possibility that researchers will now find ways to keep the stock from dying out.
Once thought to number 11,000 in the North Pacific, the slow-swimming right whales were decimated by whalers because they were easy to harpoon and floated after death. Though a few hundred may still summer in the Sea of Okhotsk in eastern Russia, the whales returning to Alaska waters probably number only in the tens.
''These animals are critically endangered,'' said Sue Moore, a whale specialist with the Marine Mammal Laboratory in Seattle, who coordinated research into the whales over the past few seasons.
The discovery of this remnant population, first reported in 1996 and described in the current issue of Science by Tynan and two other authors, has triggered a surge in research and a legal push to designate a broad stretch of the Bering Sea as habitat essential to their survival.
Using aircraft and research ships, biologists have annually plotted sightings, gathered photographs, taken tissue samples and made recordings of eerie calls with acoustic phones planted on the sea floor. At least 14 individual whales have been identified, several seen in more than one year, according to federal biologists. One device retrieved recently contained right whale calls recorded in October, suggesting that the animals stay even longer.
Next summer, federal biologists plan to conduct the broadest survey yet and want to begin tracking the whales by satellite to find where they go in winter, said Michael Payne, director of the protected resources division for the National Marine Fisheries Service in Alaska.
In another development that gives even more urgency to their plight, northern right whales in the North Pacific appear to be a separate species from right whales in the North Atlantic or the Southern Hemisphere. The findings, reported last year in the journal Molecular Biology, came after researchers analyzed DNA from 380 right whales, some of it extracted from century-old baleen recovered from whalers.
With all this new information, the Center for Biological Diversity last year petitioned the fisheries service to designate a swath of middle shelf waters in the Bering Sea as critical habitat, entitled to special scrutiny under the federal Endangered Species Act.
In the North Atlantic, where northern right whales number fewer than 300, critical habitat has already been identified to reduce the number of whales killed after getting struck by ships or tangled in fishing gear.
''We think the right whale is in a precarious situation in the Pacific,'' attorney Brent Plater said. ''We're going to have to make changes in our day-to-day life in the Bering Sea. . . . In times of the year when we know right whales are present, extra precautions are going to have to be made.''
In October, the center filed notice that it will sue in federal court if the agency doesn't make a final ruling within 60 days.
''We're still in the process of responding,'' said Payne, of the fisheries service. ''We have to do it by mid-December, and we're going to make that deadline.''
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