Daniel James, 42, has been fined $600 with $130 court costs after pleading guilty to a charge of falsely claiming to be a Ministry for Primary Industries fishery officer. He was also ordered to pay $200 in reparation.
The ministry says Mr James appeared in the Kaikōura District Court last week.
It says the court was told that Mr James approached three French tourists who had been freediving in South Bay at the end of November 2018 and told them he was a fishery officer and was there to inspect their catch.
He advised the tourists, after measuring the fish with his hands, that two of the fish were undersized and that the third was not fit to eat.
Mr James also told the trio that, by law, he should take all their equipment from them including their car and that he should send them to court.
He added that they would need to pay a $1,600 fine for the first fish and a $700 fine for the second, then told them that instead of going to court, they could give him a $200 cash donation.
"The tourists asked Mr James for a business card but were told by Mr James he was on his day off and that his cards were in the office. He then advised that the tourists needed to pay up immediately or he would make everything official, take their passports and set a court date for them to appear at," the ministry says.
"One of the tourists then drove to an ATM, withdrew $200 and gave the money to Mr James in the belief that it was a payment of a fine."