A Grand Isle commercial fisherman with six convictions of driving under the influence was sentenced to 20 years in prison for his latest DUI conviction, Jefferson Parish District Attorney Paul Connick said Friday.

Rockey Burnham, 44, was convicted as charged of his second fourth-offense DUI on April 20. Fourth-offense DUI is the most serious offense available to prosecutors under Louisiana law.

Burnham was arrested on April 28, 2015, after he crashed a boat he was piloting into moored vessels and the shrimp dock owned by Dean Blanchard Seafood, Connick’s office said in a news release.

Burnham did poorly on the field sobriety test, leading to blood work that yielded the presence of diazepam, nordiazepam and methamphetamine, according to evidence presented at the trial.

Fourth-offense DUI conviction carries a sentence of 10 years to 30 years in prison, and Judge Conn Regan of the 24th Judicial District Court opted for a 20-year sentence, to be served without the benefit of parole, probation or suspended sentence.

Because he was on probation at the time of his arrest in this last case, Burnham faces an additional seven years if his probation is revoked, Connick’s office said.

Assistant District Attorneys Lynn Schiffman and Marko Marjanovic prosecuted the case.