Satellite tags show ties between Pacific gray whale groups

For the second time in two years, scientists have tracked western gray whales -- considered a separate population from California gray whales -- from summer feeding grounds off Russia to the North America coast, challenging the assumption that western whales spent winters in the south China Sea.

A 9-year-old female as of last week had crossed the North Pacific to U.S. waters and swam south all the way to Tijuana, Mexico, apparently heading for breeding and calving rounds in lagoons of Baja California.

She's the third western Pacific gray whale tagged by the research team that has crossed the North Pacific, leading biologists to question whether they're part of an endangered, separate population that shares a feeding area or an extension of the California gray whale population.

"I don't think there's any question that there used to be a western gray whale population that went down the Asian coast," said Bruce Mate, director of Oregon State University's Marine Mammal Institute. "I don't think that there never were western gray whales. The question is whether western gray whales of that sort still exist or not."

Mate is part of an international research team that includes the National Marine Fisheries Service, the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, the Kronotsky State Nature Biosphere Reserve and the Kamchatka Branch of the Pacific Institute of Geography.

Western Pacific gray whales were hunted and by the 1970s thought to be extinct until a population was spotted off Sahkalin Island. Just 130 animals remain. They face threats from shipping and offshore petroleum development. Whales have been killed by fishing nets set off Japan.

In contrast, California gray whales, also called eastern Pacific gray whales, are a recovery success story. Their numbers were decimated by whalers but are now estimated at 18,000. They were taken off the endangered species list in 1994.

California gray whales feed in the Bering, Chukchi and Beaufort seas off Alaska in summer. They migrate down the West Coast to breed, mostly in bays of Baja California.

U.S. and Russia scientists in September 2010 attached a satellite tag to a single whale, a 13-year-old male they named Flex. Two months later, he began a journey that researchers tracked through Alaska waters to central Oregon. Scientists believe the satellite tag fell off about Feb. 4 after Flex had traveled 5,335 miles over 124 days.

Researchers in September set up again in Russia and attached tags to six whales. Four tags quit working before whales left Sakhalin Island, but in late November, young, tagged females named Varvara and Agent were tracked crossing the Sea of Okhotsk.

A week later, traveling separately, they swam around the Kamchatka Peninsula and headed east across the Bering Sea toward Alaska.

Both crossed the Aleutian Islands into the Gulf of Alaska in late December.