As blue whales feast around Farallon Islands, Coast Guard asks ships to go slow

With scores of blue whales feasting on tiny krill around the Farallon Islands, the Coast Guard is asking large ships to slow down to avoid deadly collisions with the largest animals on the planet.

Collaborating with managers of two national marine sanctuaries, the Coast Guard is asking heavy vessels - including tankers, container and cruise ships - to approach and exit San Francisco Bay at no more than 10 knots, about half their normal speed, and watch out for the leviathans that can send a spout up to 30 feet in the air.

The notices were prompted by reports from biologists stationed on Southeast Farallon Island, who spotted at least?47 blue whales in one hour on June 13, and a few days earlier, 23 of the cetaceans.

The marine mammals, up to 85 feet long, consume up to six tons a day of krill, a two-inch shrimp-like crustacean that underpins the marine food chain.

“Their enormous size dictates that they maximize feeding effort when food is available, and this sometimes takes them into dangerous waters,” Maria Brown, superintendent of the Greater Farallones National Marine Sanctuary, said in a prepared statement. “While focused on feeding, they are not likely to recognize or evade a ship’s approach.”

Getting heavy ships to slow down is intended to give the whales a chance to get out of the way and make a strike “more survivable,” said Mary Jane Schramm, spokeswoman for the Greater Farallones sanctuary.

Heavy ships make about 8,000 passes a year under the Golden Gate Bridge via channels through the Greater Farallones and Cordell Bank marine sanctuaries, which cover nearly 4,600 acres offshore from Point Reyes in Marin County to Point Arena in Mendocino County.

Scientists are concerned about blue whales because their northeast Pacific population - found within 200 miles of the California, Oregon and Washington coasts - numbers about 1,650 and has seen no significant increase since the early 1990s.

Found in oceans around the world, they are an endangered species that was driven nearly to extinction until hunting was banned in 1967.

With no natural ocean predators other than packs of killer whales, blue whales are primarily threatened by ship strikes and entanglement in fishing gear, Brown said.

At least three blue whales have been entangled since 2013, according to state and federal wildlife agencies.

California’s commercial crab season south of Mendocino County was closed last month, six weeks early, to prevent potential entanglements of whales and other marine animals, including sea turtles.

A similar request to slow ship traffic into San Francisco Bay was made in 2013, also when scientists on Southeast Farallon Island - 30 miles outside the Golden Gate - documented a concentration of blue whales in late June.

Unlike gray whales, a North Coast tourist attraction as they migrate close to shore, blue whales congregate at the edge of the continental shelf where krill are prevalent.

You can reach Staff Writer Guy Kovner at 707-521-5457 or guy.kovner@pressdemocrat.com. On Twitter @guykovner.