The condition of the whales, believed to be a mother and her calf, was diagnosed by researchers from the Marine Mammal Center in Sausalito using photos taken Wednesday in the Port of Sacramento and enlarged on computer screens.
"The injury on the female is about 2 feet long, 6 inches deep, and has sharp edges typical of a propeller wound. We don't think it's life-threatening," said Frances Gulland, director of veterinary science at the center, the group that has taken the lead on the attempted rescue of the whales. "The calf has a wound that looks a little bit more severe than the female."
The calf's wound was difficult to assess because it is on the animal's underside, below the water line, Gulland said.
Although the injuries appear to be growing, the whales will probably not need treatment if they can be returned to their natural sea water habitat, researchers said. The salty ocean water is cleaner than the fresh water in the port, helping to heal such cuts in the mammals.
Biologists planned to play the familiar sounds of humpback whales underwater on Thursday to lure the whales out of the basin and toward San Francisco Bay, Gulland said. They will play the sounds from a boat as the tide goes out.
Shipping and small boat traffic were halted in the canal, which is 30 feet deep and 200 feet wide. One freighter remained docked at the port, known primarily as an export terminal for California rice.
The next ship was not expected to dock until May 23, giving authorities time to try to escort the whales back to the Pacific, said Teresa Bledsoe, administrative clerk at the Port of Sacramento.
Biologists had feared the larger whale was entangled in fishing gear, but what appeared to be an object wrapped around it is actually blubber, Gulland said.
The wounds, which were likely suffered as the whales made their way up the Sacramento River, appear to go only as deep as their blubber, rather than their muscle.