A search continues for other members of the Katmai, a 93-foot fish processor based on Alaska's Kodiak island, said Coast Guard Petty Officer Levi Read.
The water was 43 degrees when rescuers hauled the survivors out of the raft, Read said. He couldn't speculate on how long they were in the raft because it was not known exactly when they abandoned their boat. Still, he said, several factors helped them survive.
"That takes a lot of fortitude and a lot of heart," Read said. Their survival suits, their physical condition, and an effort to keep one another semi-warm and awake all could have helped them endure, he said.
The four survivors were discovered in the raft near the Amchitka Pass, which links the Bering Sea to the Pacific Ocean about 1,400 miles southwest of Anchorage. They were being flown in a Coast Guard helicopter to nearby Adak Island.
It wasn't clear what happened to the boat.
The Coast Guard received an electronic signal at 1 a.m. from the Katmai. A search helicopter and C-130 airplane were sent from Kodiak, a journey of about 4 1/2 hours. The plane crew spotted two strobe lights in the water and dropped two life rafts. But after sunup, the searchers had seen no sign of the Katmai or its crew, Read said.
One strobe was attached to an empty survival suit and the other was attached to a floating emergency beacon that can be triggered automatically by contact with water. Vessels are required to carry those devices to signal emergencies and aid searches.
The Coast Guard did not receive a mayday call, but given the boat's remote location, it may not have been heard.
"It's hard to say whether they tried or not," Read said.
At least one fishing vessel arrived to help the Coast Guard with the search, and another was expected soon. The fishing vessel found one of the three bodies, as well as debris, survival suits, fishing gear, a buoy and a life ring, Read said.
But no oil sheen typically seen from sunken vessels had been spotted, so the Coast Guard was not prepared to say with certainty that the vessel had sunk.
The Coast Guard reported 10- to 15-foot seas in the area, with winds from the north at 34 mph. The area had a mix of rain and snow.
The Katmai was carrying a load of cod and was heading toward Dutch Harbor on Unalaska Island, Read said. Dutch Harbor is 800 miles southwest of Anchorage and about 610 miles southwest of Kodiak.
According to state permit records, the Katmai is owned by Seattle-based Katmai Fisheries. Calls to the company were not immediately returned.