Blue whales now like our local dives

Word to the whale-wise: Head south.

Once a rare sight south of Santa Barbara, blue whales have in recent years come to favor Southern California waters.

Whale watchers seeking a glimpse of the largest animals on Earth this summer will have the best chances off the coast of Orange and San Diego counties and northern Baja California, according to marine biologists.

“Some ebb and flow is normal for animal populations in general,” said Mike Bursk, a biologist with the Ocean Institute in Dana Point. “But in the last decade there’s been a noticeable shift. There’s been a movement of the herd.”

Dave Anderson, owner of Captain Dave’s Dolphin Safari in Dana Point, has noticed the change.

“Five or six years ago, seeing a blue whale was newsworthy,” he said. “If we saw a blue whale out here we were on TV, people were calling us.”

Last summer he logged 440 blue whale sightings.

Capable of traveling 100 miles a day, the blue whales migrate north each summer from their winter grounds off Central America.

Their numbers along the Eastern Pacific coast have increased steadily since commercial whaling of the species was outlawed in 1966.

The blue whale’s worldwide population is estimated at 10,000, though scientists say as many as 300,000 of the aquatic giants swam the world’s oceans before whaling.

In the last two decades, Central California became known as “the best place in the world to see the largest animal on Earth predictably,” said Nancy Black, marine biologist with Monterey Bay Whale Watch, which operates daily tours.

The blue whales were known to feed consistently in the krill-rich waters of deep Monterey Bay Canyon from July to October, Black said.

But in the last two years, the number of blue whales spotted by those aboard the company’s two powerboats has dropped to between 20% and 30% of normal levels.

Black said she was relieved when they saw their first two whales of the season at the end of June.

“We kind of got used to the blue whales because they had been more predictable,” she said. “Now when we see them it’s going to be a bigger deal.”

Scientists are studying the migration patterns, but offer few explanations for the whales’ shift south. Bursk, of the Ocean Institute, said there had been little research into the causes of the shift.

“Anyone who tells you they know why the shift is taking place is wrong,” he said.

But others suggested the whales simply may be going where krill, their nearly exclusive food source, are more plentiful.

“We’re trying to determine if this is part of a cyclical change that is normal or whether it reflects a decline in krill as a result of climate change, which is something we’d be much more concerned about,” said John Calambokidis, a biologist with Cascadia Research, a nonprofit group based in Olympia, Wash., that has studied blue whales off the West Coast since 1986.

Using inflatable pontoon boats with outboard motors, Calambokidis and a small staff of researchers track individual members of the blue whale population by taking photos of the distinctive dark markings on their sides, which he said are “more detailed and reliable than fingerprints.”

The research group’s photo identifications have shown that the length of the whales’ migration -- from as far north as the Gulf of Alaska to Central America -- hasn’t changed. But they are spending more time feeding off Southern California.

On an afternoon this summer, a group of mostly out-of-state tourists aboard Anderson’s Dolphin Safari in Dana Point marveled at a blue whale that emerged and puffed air and water out of its blowhole about 30 feet from the boat.

The whale was nearly twice as long as the 35-foot catamaran.

“I never thought I’d ever see one in my lifetime except on tape,” said Terry Hires, an artist on vacation from Kansas City.

But the whales’ prevalence in Southern California is not without peril. They have entered waters populated by fishing boats and cargo ships, and have sometimes collided with the large vessels.

At least five blue whales have been killed off the California coast after being hit by ships since 1980, according to a 2006 report by the National Marine Fishery Service.

In the last few years, blue whales have fed on krill along the edge of an underwater canyon about 12 miles off Long Beach Harbor, said Dan Salas, operator of Harbor Breeze Cruises in Long Beach, who two years ago christened a catamaran specially designed to view blue whales.

The spot also happens to be an inbound shipping lane at one of the world’s largest container shipping ports.

In the six weeks since the blue whales began appearing near Long Beach Harbor this year, Salas has missed spotting blue whales only three times, and he charters two or three trips a day seven days a week, he said.

Their presence is a thrill unmatched in his 20 years as a captain, he said, but he is concerned for their safety. “They’re in serious danger of getting hit,” he said.

Mat Curto, captain of the Condor Express, who charters daily whale-watching trips out of Santa Barbara Harbor, used to encounter more than 40 blue whales a day. Since 2003 the sightings have tapered off to only five or six.

Curto said he still holds out hope that more blue whales will come to feed on the krill in the Santa Barbara Channel.

He sees the red-orange clouds that indicate a mass of krill below the surface, and hopes the whales will find them too.

“We were the guaranteed spot,” he said. “But we’re learning that there is no guarantee with nature. You’re dealing with wild animals.”

tony.barboza@latimes.com