RIO VISTA, Calif. — Six boats gently drove a reluctant humpback whale late Friday afternoon from the shallow slough where it had taken up residence and began herding the wayward creature down the Sacramento River toward the Pacific Ocean.
As darkness fell, however, the 40-ton mammal lost its escort of small craft just north of the Rio Vista drawbridge. A search was under way, and rescuers were confident that, at worst, they could relocate the lost leviathan after daybreak and resume the drive downriver.
Guiding the whale out of the slough was a major breakthrough in efforts to save it. Marine biologists had feared that the mammal would die in the mile-long channel from continuous exposure to freshwater, which could harm its skin or cause brain damage.
Passes Under Bridge
"It's through, baby. It's through!" shouted marine biologist Mark Ferrari as the 40-foot whale passed under a small bridge that seemed earlier to be blocking its exit from the dead-end channel.
Choosing one of three openings dredged during the night to clear a large enough passageway, the giant mammal nosed its way cautiously forward. For several minutes, the whale appeared to be stuck in the narrow gap and waved its 15-foot pectoral fins in the air.
But spurred on by the boats behind it and the noise of clanging metal pipes in the water, the rare whale swam under the bridge and entered the main river channel, heading toward the sea.
As the whale was driven downstream, traffic on the drawbridge was halted for nearly two hours in hopes that the giant would cross under.
However, after dark, the whale eluded its escort about half a mile north of the bridge. As the night wore on, rescuers searched unsuccessfully for the creature by the light of flares fired from a U.S. Coast Guard patrol boat and the searchlight of a California Highway Patrol helicopter. Volunteers were urged to gather at the riverbank to listen for it.
One of fewer than 10,000 humpbacks remaining in the world's oceans, the whale, apparently having lost its way on its migration from Alaskan to Hawaiian waters, swam into San Francisco Bay 16 days ago and headed up the river. Last Saturday, it negotiated the pilings under the small Liberty Island Bridge and entered Shag Slough, about 60 miles from the ocean.
On and off for more than four hours Friday, volunteers in the six boats attempted to herd the creature under the slough bridge.
Display of Anger
At one point, the operation was halted for an hour, when the animal slapped one of its giant pectoral fins on the surface of the water half a dozen times in an apparent display of anger.
But as the rescue operation resumed with a dangerous game of chicken, two of the boats repeatedly approached within several yards of the whale as it swam in the shadow of the bridge.
Several times, the whale swam partially under the boats and blew noisily in the air. But it left the vessels alone.
Finally, about 4 p.m., the whale slowly moved forward into one of the 20-foot-wide openings between the pilings. The dredging had increased the depth of the gap from nine feet up to 18 feet.
'Looks Like He's Stuck'
"He's floundering around in there," Ferrari called out from his vantage point on the bridge, as he helped direct operations over a two-way radio. "He's halfway in there, and it looks like he's stuck."
Briefly, volunteers in the six boats banged on pipes suspended in the water, using the oikomi method of herding dolphins and small whales developed in Japan. At the same time, one of the lead boats moved slowly forward within a few yards of the whale to urge it onward.
As the whale broke free and swam through, cheers went up from the volunteers, reporters and photographers gathered on the levee.
Rescuers hung ropes weighted with sandbags from the bridge to serve as a makeshift gate to keep the whale from reentering the slough.
"The way the whale is being moved involves a little irritation, by design," said Ken Norris, a marine biologist from the University of California, Santa Cruz. "The trick is to keep a little pressure on him so he'll go in the right direction.
"There was irritation when he blew water into the air too, but it's either that (irritate the whale) or let him die."