Updated

An Alaska salmon boat skipper who killed endangered Steller sea lions with a shotgun and hindered an investigation has been fined $20,000 in federal court.

Jon Nichols, 31, of Cordova, was sentenced Tuesday to five years' probation, three months of home confinement and 400 hours of community service.

U.S. Magistrate Judge Deborah Smith also ordered Nichols to publicly apologize in a national commercial fishing magazine.

One of Nichols' crewmen, Theodore "Teddy" Turgeon, 21, of Wasilla, also shot the endangered animals. He was sentenced to four years' probation, one month of home incarceration and 40 hours of community service. He was fined $5,000.

Steller sea lions are the largest members of "eared" seals family, according to the Alaska Department of Fish and Game and can live to be 20 to 30 years old. Females can reach nearly 580 pounds (263 kilograms) and males up to 1,245 pounds (565 kilograms) in the North Pacific Ocean. They get their name from the big males' intimidating roar as they protect harems.

Steller sea lions are voracious feeders of fish. Adults eat upward of 6 percent of their body weight per day. They target fish that are always available such as pollock and cod as well as seasonally available fish such as herring and salmon.

After a dramatic decline in numbers of Steller sea lions in Alaska, the National Marine Fisheries Service in 1990 listed them as threatened. The agency delisted the eastern population in November 2013.

Federal officials investigated in 2015 after 15 Steller sea lions were found dead at the mouth of the Copper River near Cordova. Huge runs of sockeye and king salmon return to the river, starting in late spring.

Nichols was captain of the fishing boat Iron Hide. Investigators determined that between May and June 2015, Nichols regularly ordered crewmen to shoot at Steller sea lions using shotguns belonging to him and Turgeon.

Nichols shot animals himself and drove the boat toward sea lions to allow Turgeon or other crew members to get a better shot, prosecutors said.

"This crew admitted to shooting over 50 rounds at sea lions and killing at least three of the 15 dead sea lions that rolled up in 2015," said Assistant U.S. Attorney Aunnie Steward, who prosecuted the case.

The court noted that other Copper River fishing crews likely also shot sea lions, Steward said.

"I would say collectively what was happening in that fishery at that time was some of the worst we've seen in decades, if not ever," she said.

When Nichols learned that federal officers were looking into the sea lions deaths, Nichols obstructed the investigation by coordinating false stories among crew members.

Turgeon, with the encouragement of Nichols, lied to enforcement officers. He told them no sea lions were shot and that the Iron Hide carried no guns, prosecutors said.

Magistrate Smith commented that she hoped the sentences would provide deterrence to others, Steward said. The magistrate also noted that Nichols' obstruction was particularly serious.

"It went on for about 15 months," Steward said. "The captain was working the whole time to keep his crew lying to federal agents," she said.

Nichols and Turgeon in June pleaded guilty to one count of illegal take of marine mammals.