Two whales lost in the Sacramento River have made progress toward their ocean home, but rescuers are still afraid of encounters they might have with large ships as they near San Francisco Bay.
The mother humpback whale and her calf were spotted Monday morning near the Benicia-Martinez Bridge, about 45 miles (72 kilometers) from the Pacific, said Carol Singleton of the Governor's Office of Emergency Services.
The pair had traveled about 24 miles (39 kilometers) in 24 hours, but their pace had slowed. They were first spotted May 13 and got as far as 90 miles (145 kilometers) inland to the Port of Sacramento before turning around.
Biologists hope that getting the whale into more brackish water after more than two weeks in the river could help ease the physical strain they have suffered from long exposure to fresh water.
They could not predict whether the whales would keep moving, though, and officials did not plan to take any action to prod them toward the Golden Gate Bridge.
"It's still anybody's guess. The whales are going to decide what they're going to do and how they're going to do it," said Bernadette Fees, deputy director of the California Department of Fish and Game.
Thus far, the U.S. Coast Guard boats monitoring the whales as they swim down river only have had to deal with recreational boats and windsurfers. But as the whales get closer to the bay, they will encounter large oceangoing vessels that could harm them.
"We will try to keep a safe zone around them," said Greg Hurner, a senior adviser with the California Department of Fish and Game. Boats also were being positioned to block entrances to a number of tributaries and sloughs, where the whales are at risk of getting stuck in shallow mudflats.
Both whales have gashes - likely suffered from a run-in with a boat's keel - that have also worsened during their river stay. But veterinarians believe antibiotics injected into the whales Saturday could slow the damage, and scientist were ready to administer a second dose.
The calf also appears to be more active, which is an encouraging sign, they said.