Joe St. Georges, a 25-year department veteran, suffered severe hand and arm injuries but was in good condition at County USC Medical Center Friday, said Los Angeles fire Capt. Steve Ruda.
"He has significant injuries, bites and punctures, to his hand and arm and is being seen by a specialist," Ruda said.
The dog, nicknamed Vernon after the Southern California town where he was found, did not have a name tag or computer chip, said Sgt. Charles Miller of the Southeast Area Animal Control Authority in Downey.
The dog was quarantined to be monitored for rabies, but "appears to be well-maintained and cared for," Miller said.
At least 50 firefighters responded to reports that the dog was in the river. For an hour, firefighters stood at the top of the steep, concrete banks, throwing life vest and float rings, hoping the dog would grab on. Most of the time, the canine walked along a pipe or ledge in the center of the river, sometimes slipping. One firefighter got into the river and tried to catch him, but the dog took off. Soon the pipe was submerged.
When the helicopter hovered overhead, the dog scrambled to the side of the river and tried to climb the sides, only to slip each time.
The 50-year-old St. Georges finally splashed down from the helicopter, wrestled with the frightened canine and lifted it to safety.
At a late afternoon news conference, helicopter pilot Scott Bowman said St. Georges took a muzzle with him but he wasn't able to get it on, "so he decided to go for the capture."
Miller said the dog had some scrapes and worn nails, but was otherwise fine.
"He was fearful when he first got here, understandably. He went through a big ordeal," Miller said.
The dog will be quarantined for 10 days, unless the owner shows up with proof of rabies vaccination, Miller said. Then, the dog could be monitored at home. If the owner doesn't show up, officials will try to find the dog a new home.
Storms that started Monday have already dropped up to 8 inches of rain in Los Angeles County, the National Weather Service reported.