Gray whales are being sighted this week off of Sausalito and Tiburon, a continuation of treks into San Francisco Bay that are relatively new, whale watchers say.

"I saw the whale (Monday) in Racoon Strait," said Klaus Meinberg of Tiburon, who managed to shoot photos of the massive mammal, which he estimated at about 30 feet long. "It went right by our house swimming east. It came up four to five times to catch some air."

On Sunday morning people gathered along the shores of Sausalito to watch a whale, said Bill Keener, co-founder of Golden Gate Cetacean Research.

"There were people along the Sausalito bike path watching it," the Corte Madera resident said. "It was definitely there."

It s not known if the different sightings were of the same whale. What is known is that gray whales are migrating north now and for the past several decades they have been coming into the bay more often, said Birgit Winning, executive director of the Fairfax-based Oceanic Society. The reasons are not clear.

"We are seeing increased sightings in the bay and that has been the case since the 1970s," she said. "All along the West Coast they are entering bays more often. It could be they are hiding from predators or using the bays as a resting site. Their population has been growing since the 1970s."

In mid-April, the Oceanic Society plans to launch a study on whales in the bay to determine which areas they are going to most.


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Racoon Strait, between Tiburon and Angel Island, could prove to be a hot spot, said Mary Jane Schramm, spokeswoman for the Gulf of the Farallones National Marine Sanctuary.

"It seems to be one of their favorite hideouts," Schramm said. "It s not clear if they prefer it there or if they are just more readily visible in that location."

The whales that enter the bay seem to be juveniles or young adults.

"It could be these are teens checking out the neighborhood," she said. "They might be curious."

The whales are in the midst of their migration, which takes them some 10,000 miles each year -- the longest of any mammal. They spend about a third of their lives migrating, scientists say.

The migration is driven by food. The Bering and Chukchi seas off Siberia and Alaska provide a feeding ground for the whales, but as winter approaches and days grow shorter and colder, the whales begin their journey south to the warmer climate of Baja California. The whales are able to swim 20 hours at a time.

While they travel together for the journey, the whales separate at their destination. After up to three months basking in the warm waters off Baja, some with newborn calves, they migrate back to Alaska, which is what is occurring now.

While watching the whales from a distance is fine, Schramm urged bay boaters not to get too close. She said boaters shouldn t approach within 300 feet, cut across a whale s path, make sudden speed or direction changes or get between a whale cow and her calf.

"They are traveling thousands of miles, give them a break and let them rest," she said.

Contact Mark Prado via email at mprado@marinij.com