RIO VISTA – Scientists became increasingly concerned about the health of two wayward whales Tuesday as the mother whale and her calf spent a second day circling near a Sacramento River bridge about 70 miles from the Pacific. Both whales are wounded, apparently from a run-in with a boat’s propeller, and veterinarians have recently observed changes in the condition of those wounds, according to the U.S. Coast Guard. “The wounds appear to have worsened over time and their skin has changed from smooth and shiny to irregular and pitted,” said Frances Guiland of the Marine Mammal Center. Fresh water from the Sacramento River could hamper the whales’ recovery, biologists said. 160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! Skin samples taken from the mother whale Monday were sent to out-of-state labs to assess her general health and help identify her population stock. Scientists and the U.S. Coast Guard tried to position more than two dozen boats ahead of the whales in an effort to keep them from swimming any farther back up the river on Tuesday. Some crews tried to herd the two humpbacks by banging metal pipes beneath the water in an effort to drive them downstream. The challenge, officials said, was encouraging the pair to return to salt water quickly but without resorting to tactics that could upset the wounded whales.