RIO VISTA – Marine biologists temporarily halted efforts to coax two lost, injured whales back to the Pacific on Thursday, after the sounds of clanging pipes, feeding humpbacks and killer orcas failed to induce the pair to head back to saltwater. The mother whale and her calf were last spotted about 70 miles from the ocean, in an area of the Sacramento River where they have been circling for several days, said Carrie Wilson, a biologist with the state Department of Fish and Game. Marine biologists had planned to broadcast recordings of attacking orcas to scare the wayward whales back to saltwater Thursday morning, but decided instead to give the pair a break. “We don’t want to do anything that will impose stress on them today,” Wilson said. “We do not want them to become habituated or desensitized to the different types of things we’re doing to coax them down the river.” Rescuers said Thursday they planned to continue efforts to move the stranded whales over Memorial Day weekend if the animals had not started moving on their own. The U.S. Coast Guard crews would keep a 500-yard buffer zone around the whales to keep boats away. They expected crowds to gather along the riverbanks to catch a glimpse of the humpbacks. The whales apparently took a wrong turn during their annual migration to feeding grounds in the northern Pacific. They traveled 90 miles inland to the Port of Sacramento before turning around. They were making progress Monday until they reached the Rio Vista Bridge and began swimming in circles.160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! Today, scientists planned to spray fire hoses at the whales, a tactic that has never before been attempted. Officials do not know if the technique will attract or repel the animals, said Frances Gulland, who is leading the campaign to move the whales back to the ocean. The physical condition of the whales had not changed much Thursday, but their wounds – apparently sustained during a collision with a boat’s propeller – continued to deteriorate, she said. The rescuers are working on a plan to inject the whales with antibiotics to help their wounds heal. Scientists are still developing the drug and will likely use a syringe attached to a pole or a dartgun to administer it, Gulland said. Scientists tried playing different underwater sounds on Wednesday evening. The lost whales did not respond to recordings of fellow humpback whales or blood-thirsty orcas, but a noisy mix of unnatural sounds caused the pair to back away, Wilson said. The stranded whales also didn’t respond to the banging of banging metal pipes or a small fleet of boats trying to herd them downstream earlier Wednesday. read more