Two gray whales visited downtown Seattle yesterday, swimming as close as 50 yards from the waterfront piers along Elliott Bay.

One of the whales cruised past the Seattle Aquarium, catching visitors' attention with a trail of bubbles and then a brief glimpse of its back breaking the surface.

"I saw the whale spout as it was heading north," said aquarium biologist Tim Carpenter.

The West Coast grays are northbound now on their annual migration between winter breeding grounds off Mexico and summer feeding grounds off Alaska.

Scientists think that because of population growth, more gray whales are venturing to inland waters such as Puget Sound to feed. Grays are bottom feeders that churn up the ocean floor and use baleen — bony plates in their mouths — to strain out the tiny sea creatures they feed on.

At least nine grays are now in the state's inland marine waters, according to a news release from Cascadia Research, a nonprofit research institute based in Olympia. They include a half-dozen whales in the Whidbey Island area, where they gather to feed on ghost shrimp; two in southern and central Puget Sound; and one in Hood Canal.

Six grays, identified by markings on their skins, have returned annually to Whidbey since at least 1991, according to Cascadia researcher John Calambokidis.

Meanwhile, Cascadia reported yesterday that a dead gray whale found Monday on a Whidbey Island beach apparently had suffered a head injury, perhaps from a vessel.

"Because the animal was thin and results of other tests are not available, it is possible other factors were involved as a cause of death," Cascadia said.

The whale was a juvenile male about 25 feet long, probably an undersized yearling. It was the first confirmed stranding of a gray whale this year in Washington state. As many as 28 grays wash up dead on state shorelines each year, the release said.

In addition to Cascadia researchers, scientists with the National Marine Fisheries Service and the state Department of Fish and Wildlife participated in a necropsy of the animal. A pathologist with the British Columbia Ministry of Agriculture and Food also was present.