Fisheries NZ says the incident is "disappointing" and it'll be interviewing the crew from two vessels.
The man had to be winched to safety from rocks on Auckland's Bethells Beach.
Two helicopters and a search and rescue team were involved in the operation.
If you buy seafood from unreputable sources you could end up facing charges.
"We can only have so many government observers on vessels, and they can't be awake 24/7."
They have been picking up half a dozen illegal set nets every week lately, in Tāmaki Makaurau Auckland.
"When I'm out there, I forget about it."
The data raises questions about reassurances from the commercial fishing industry that most of its trawling is done on muddy "featureless" sea floors.
The group pleaded guilty to all charges under the Fisheries Act.