SAN FRANCISCO — Two lost whales were on the move again Sunday toward the Pacific after lingering for a week near a Sacramento River bridge about 70 miles from the ocean, officials coordinating the rescue said.
The mother humpback and her calf passed under the Rio Vista Bridge just before 2 p.m. and were spotted about 14 miles downriver near Pittsburg, Calif., about 6:30 p.m., said Greg Hurner, senior advisor with the state Department of Fish and Game.
Six boats were following the pair, nicknamed Delta and Dawn, as they reached Decker Island, the farthest point downriver the marine mammals have traveled since departing the Port of Sacramento last weekend.
Scientists have no clear idea why the whales began moving again after frustrating biologists' weeklong efforts to urge them seaward using a variety of tactics, said Greg Renick, spokesman for the California Office of Emergency Services.
Before the pair headed south, veterinarians used sponges attached to a long pole to swab skin cells from bumps resembling blisters or lesions on the mother and calf.
The humpbacks' long exposure to fresh water has led to serious skin damage, biologists said, making them vulnerable to germs they would not encounter in their native saltwater habitat.
"We really need to try to get them back into a more appropriate environment so they can start healing," said Trevor Spradlin, a marine mammal biologist with the National Oceanic and Atmospheric Administration.
The bumps may be the result of an infection from bacteria, a virus or fungus, but scientists won't know for sure until they examine the skin cells under a microscope, Spradlin said.
Deep gashes in both whales -- likely suffered from a run-in with a boat's keel -- have also worsened rather than healed outside their ocean home. But veterinarians believe antibiotics injected into the whales Saturday could slow the damage.
Scientists won't know for several days whether the medicine is having a positive effect, Spradlin said. Although rescuers continued to monitor the whales' health, they had otherwise halted operations over the long Memorial Day weekend to let the whales rest.