Two whales that lost their way more than a week ago spent a second day circling near a Sacramento River bridge Tuesday, about 70 miles from the open waters of the Pacific Ocean.
Both whales are wounded, apparently from a run-in with a boat’s propeller.
“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. Skin samples taken from the mother whale on Monday were sent to out-of-state labs to assess her general health and help identify her population stock.
Some crews in the more than two dozen boats blocking the humpbacks’ path up the river tried herding the mother and her calf downstream by banging metal pipes beneath the water.
The challenge, officials said, was encouraging the pair to return to salt water quickly but without resorting to tactics that could upset the whales.
“Stressing even a healthy whale is not good. Stressing an injured whale is worse,” said Brian Gorman, a spokesman for the National Oceanic and Atmospheric Administration.
The humpbacks, nicknamed Delta and Dawn, had traveled 90 miles inland more than a week ago before turning around at the Port of Sacramento on Sunday. They were making progress Monday until they reached the Rio Vista Bridge and began swimming in circles.
Scientists theorized the whales began circling because vibrations from traffic upset them. The pair could not be coaxed forward even when the drawbridge was raised to halt the flow of vehicles.
Scientists have been watching the two closely because their route includes sloughs leading to muddy deltas where the whales could become lost and trapped.
The pair also face a couple more highway bridges between Rio Vista and San Francisco Bay, including the Golden Gate.
Federal officials have authorized researchers to fire darts carrying a satellite tracking device beneath the mother’s fin to monitor her location, but two days of gusty winds and choppy waters have delayed the tagging.