In November, a Supreme Court jury found James Joseph Landry, 67, of Cape Breton guilty of manslaughter.
Landry is one of four linked to the 2013 death of Phillip Boudreau.
Evidence at the trial suggested Landry and the other two crew on the fishing boat Twin Maggies found Boudreau fiddled with their lobster traps.
Co-prosecutor Steve Drake said the Twin Maggies rammed Boudreau's boat three times at the mouth of Petit de Grat harbour on June 1, 2013. Prosecutors also said Landry fired four shots from a rifle, and one hit Boudreau in the leg.
Drake told the court that Boudreau's boat overturned after it was rammed the third time, and he was then hooked with a fishing gaff and dragged out to sea before he was tied to an anchor.
Boudreau's body has not been found.
Landry was charged with second-degree murder. Instead the jury found him guilty of manslaughter, which does not carry a mandatory life sentence.
The trial was filled with dramatic testimony, including videotaped statements from Landry, telling police his role in the attack that day.
Landry's lawyer has suggested his client took blame for parts of the attack that he didn't do, to protect the two other crew members — his son-in-law and another deckhand, who have young families.
Thursday's sentencing will close one chapter in this story. But three others still face charges:- The two men on the Twin Maggies that day.
- The boat's owner, who is Landry's daughter-in-law.