Massive blue whales spotted unusually close to shore off Del Mar and La Jolla were likely attracted by an unusually abundant supply of krill, the result of this summer's upwelling of cold ocean water, according to the executive director of the Birch Aquarium.
A pod of as many as nine blue whales was spotted Thursday.
Nigella Hillgarth, the head of the aquarium, said blue whales, the world's largest mammals at 100 feet, are twice as long as the gray whales usually seen near land in San Diego. They also have less regular migration patterns than gray whales, she said.
Hillgarth said she saw the spouts of at least three or four blue whales off Scripps Pier.
"This year, we've seen them closer than usual," Hillgarth said. Normally, whale-watchers have to go at least seven miles out to see them, she said.
The reason for their proximity is probably the same upwelling that resulted in the cold water encountered by beachgoers in recent months, according to Hillgarth.
The cold water from the ocean floor is swirled upward by colliding currents, bringing with it "nutrient-rich water for krill, which the blue whales are having a good time eating," she said.
Krill are shrimp-like crustaceans that whales feast on.
Hillgarth said experts at the Scripps Institution of Oceanography told her the upwelling is expected to last to the end of the month, so the blue whales could stick around until then.
