Biologists held out little hope for three gray whales trapped by 6-inch-thick arctic ice off the Alaskan Coast as temperatures plunged and their food supplies ran low.

The California gray whales continued to swim several hundred feet offshore Thursday near Point Barrow, using two holes in the ice to breathe, said Geoff Carroll, a wildlife biologist for the North Slope Borough.Carroll, who made an observation flight, estimated the holes were about 15 by 30 feet, giving the whales barely enough room as they rose to breathe every four minutes or so. Open water lay more than four miles away.

Biologists believed time was running out for the grays as nighttime temperatures dropped to 13 degrees below zero, threatening to shrink the whales' breathing space.

"They eat a lot and they have to keep moving," Carroll said. "I'm sure they're going to eat everything that's there before very long." He said the whales eat plankton from the ocean floor.

The only answer would be an icebreaking ship to free the whales, Carroll said, but renewed efforts to contact an icebreaker thought to be in the area failed.

Biologists believe the whales were migrating from the Beaufort Sea to their winter grounds off the Mexican coast when they were trapped.

Several vessels, including a Coast Guard icebreaker, were delayed by arctic ice this month and last.