May 23 2016

Humpback and blue whales feeding in record numbers off SF coast

humpbackAn unusually large number of humpback whales like this one have been seen over the past two weeks in San Francisco Bay. Photo by Lauri Duke.

By Peter Fimrite

Record numbers of humpack and blue whales are feeding off the coast of San Francisco in a display of gluttony virtually unprecedented for this time of year, marine scientists fresh off a weeklong study near the Farallon Islands confirmed Sunday.

The researchers on the 208-foot-long Bell Shimada, which is now docked at Piers 30 and 32 along the Embarcadero, counted between 30 and 60 humpbacks a day and about 10 blue whales over the past seven days. Those numbers are far higher than normal for this time of year, based on similar studies done over 13 years.

“We don’t know if it’s food-driven or water-temperature- or climate-change-driven,” Jan Roletto, research coordinator for the Gulf of the Farallones National Marine Sanctuary, said of this month’s massive numbers of hungry humpbacks.

Last year was also a big year for humpbacks. “They’ve been showing up earlier and earlier” every year, she said.

The researchers suspect the giant cetaceans are following prey — including the tiny shrimp-like creatures known as krill, anchovies and schools of small fish. Several humpbacks were seen over the past few weeks feeding in San Francisco Bay near Fort Point, a highly unusual activity for the whales, which generally prefer to be well offshore.

The weeklong expedition, which covered some 50 miles of ocean from Half Moon Bay to Bodega Bay, was an attempt by scientists with the Greater Farallones National Marine Sanctuary, the Cordell Bank National Marine Sanctuary, and Point Blue Conservation Science to document wildlife populations and trends in the area, which is known to be one of the world’s most abundant marine ecosystems.

Marine scientists describe their work on the research vessel Bell M. Shimada

Media: / San Francisco Chronicle

The researchers took water temperatures; measured ocean acidification; counted birds, whales and other marine mammals; and calculated the amount of krill and other marine organisms to determine what drives sea bird and whale abundance. The researchers also took measurements of ocean nutrients, including testing for harmful algal blooms like the one last year that poisoned sea lions and forced closure of the Dungeness crab season.

“We are coming out of El Niño, so we’re hoping to determine what happens in the ocean after an El Niño,” Roletto said.

So far this year, ocean temperatures appear to be normal, she said. That’s a welcome change from last year, when temperatures reached 6 degrees above normal. The high temperatures apparently contributed to record deaths of seabirds and sea lions, a profusion of alien species and poison-spewing algal blooms. No harmful algae has been found this year, she said.

Besides the whales, mass quantities of zooplankton known as doliolids were found in the water, often clogging scientist’s nets. The tube-like creatures thrive in warm bands of water. The team also found that the bodies of some krill have shrunk because of a lack of phytoplankton, their primary food source. Krill in other areas, particularly between the Farallon Islands and the ocean outcropping called Cordell Bank, were much bigger.

Along the Golden Gate Strait in San Francisco, this videographer captured a double breaching when two massive humpback whales shot out of the glistening water simultaneously.

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