PORT GRAVINA, Alaska, February 19, 2002 (ENS) - A booming shark population and declining seal and sea lion populations in Alaskan waters could be a sign of global warming, argued researchers at the annual meeting of the American Association for the Advancement of Science (AAAS).

A spotter in an Alaska Fish and Game plane on a recent survey of sea otters estimated there were hundreds of shark fins in the small bay near Port Gravina, Prince William Sound. More sharks mass unseen below the surface, feasting on a run of salmon returning to spawn in nearby rivers and creeks.

"That aerial count would be a high number of sharks in one spot for any place in the world," said Vince Gallucci, University of Washington professor of fisheries and aquatic sciences. Gallucci, who has studied shark population dynamics for more than a decade, the last two years in Alaska, organized the Saturday AAAS session "Not Enough Sea Lions, Too Many Sharks: Global Warming Signal?"

In the last two years of work in Prince William Sound, with cooperation from the Alaska Department of Fish and Game and the National Marine Fisheries Service, Gallucci said six salmon sharks an hour could be caught during certain times of day. Sometimes, lines were in the water less than two minutes before a salmon shark bit.

The number of Pacific sleeper sharks encountered by halibut fishing vessels has increased every year since 1997, more than doubling according to a database made available to Gallucci by the Pacific Halibut Commission.

"Fishermen wouldn't forget 200 pound animals bending hooks and wrecking their nets," Gallucci said, displaying a No. 3 steel halibut circle hook almost straightened by a salmon shark.

No one knows how many sharks there are because the necessary surveys have not been done. Fieldwork by Gallucci and colleagues, and wildlife surveys by others, lead Gallucci to say top predators in Alaska's sub-arctic waters have shifted to a new balance, with sharks outnumbering pinnpeds - animals with finned feet such as sea lions and seals.

"Increases in salmon sharks and Pacific sleeper sharks, both sub-arctic northeast Pacific shark species, don't represent ecological invasions and they aren't range extensions since both sharks are endemic," Gallucci said.

He believes population changes are tied to decades long swings in climate and continuing global warming, which have helped change the populations of fish these animals eat.

Climate conditions in recent decades have favored salmon in Alaskan waters for a number of years and heavy hatchery production has added millions more fish, to the benefit of both pinnipeds and sharks. However, commercial fishing of pollock in competition with sea lions may have benefited sharks, Gallucci added.

"Sharks, being the more efficient eaters, just may be able to take greater advantage of changes in the food that's available," Gallucci said.