SACRAMENTO — After a wandering, two-week voyage up the Sacramento River, a pair of humpback whales steamed purposefully into San Francisco Bay on Tuesday in what experts hoped would be a last dash to the ocean.
The pair, now recovering from wounds that were probably caused by a ship's propeller and the ill effects of a prolonged freshwater sojourn, zipped through the formidable currents of the Carquinez Strait and into the north bay before noon.
By late afternoon, they had passed under the Richmond-San Rafael Bridge and were within about 10 miles of the Golden Gate Bridge and the Pacific Ocean.
But experts cautioned during an afternoon news conference on the shorefront campus of the California Maritime Academy in Vallejo that many perils could still await the mother and calf in the bay's busy waters.
Commercial ship traffic and high-speed ferries pose potential obstacles. So do wrong turns.
"There's a lot of places where they could get themselves into trouble before they get out the Golden Gate," said Rod McInnis, southwest regional administrator of National Oceanic and Atmospheric Administration's Fisheries Service.
Government patrol boats continued to maintain a 500-yard safety zone around the two whales. Ferry companies willingly agreed to slow speeds near the whales, and the Coast Guard was broadcasting alerts to cargo ships.
Coast Guard Lt. Cmdr. Jon Copley said ship captains can't escape the fact that, for now, "we have a marine mammal crossing out there."
No one knew what prompted the wandering pair to head in the right direction.
"There are lots of theories, believe me," McInnis said.
First spotted in the delta May 13, the whales swam all the way to the Port of Sacramento, 70 miles from the Pacific Ocean. They stayed there for days, delighting crowds who massed on the levees, before turning tail south 10 days ago.
The whales abruptly stopped at the Rio Vista Bridge on May 20, and then swam in circles for days, seemingly spooked by the steel structure's car noise. They defied attempts by a growing armada of government vessels to herd them with clanking pipes, recordings of attacking orcas and finally a fireboat's spray.
Such attempts ceased for the Memorial Day weekend, though rescuers Saturday administered a dose of antibiotics to each whale using foot-long hypodermic needles fired from a .22-caliber rifle.
On Sunday, the pair scooted under the Rio Vista Bridge, about 50 miles from the ocean, without any coaxing. Within a few hours, they had traveled about 20 miles to the brackish waters at the delta's western edge.
By Monday they were near the Benicia-Martinez Bridge, where big crowds turned out on the shore and in boats. The Coast Guard had to yank a couple of swimmers after they tried to get up close and personal.
The rushing waters of the Carquinez Strait proved no big deal Tuesday, and the whales zipped past a delighted pack of rescue team leaders who were assembled at the maritime academy at 10:30 a.m.
Worried that the pair might erroneously move into the gaping mouths of the Napa or Petaluma rivers, rescue crews tried some "blocking techniques" to turn the whales south, Copley said.
If winds drop today as expected, authorities hope to administer additional doses of antibiotics, attach a satellite tracking tag to the mother and perhaps take samples, including one to see if the calf is still nursing.
There were no plans to renew herding efforts when the animals hit the heart of San Francisco Bay. Instead, the government flotilla planned to provide a "security bubble."
If the whales got into trouble, the armada would intervene, McInnis said, but added, "We're counting on the whales to find their way."