The group representing South Island commercial eel fishermen is investigating the fishing of tame, 80-year-old eels from Lake Moeraki, in South Westland.
Even though the lake is a scenic reserve and within a World Heritage site, the fishing was allowed under the current law.
Eco-tourism operator Gerry McSweeney, who operates the Lake Moeraki Wilderness Lodge at the outlet to the lake, said it should be illegal to take eels from a protected area.
South Island Eel Industry Association spokesman Bill Chisholm said this week they were investigating.
Mr Chisholm said it did not appear any rules had been broken, but he was looking into whether the industry's own code of practice had been breached.
He said it appeared a fisherman, probably commercial, had been told not to fish near the tame eels.
''(But) They got a bit too close.''
Mr Chisholm asked Dr McSweeney to forward a map of which areas he did not want fished in future.
"Anyone with tame eels can send us their details to ensure our members can avoid them.''
However, he stressed the association did not cover customary or recreational eel fishermen.
Responding to criticism from Dr McSweeney, he said long-fin eel numbers were "definitely increasing'' on the West Coast and the rest of the country.
"They are not threatened, not declining, not on the road to extinction. They are stable or increasing. Scientific evidence demonstrates that.''
Mr Chisholm said commercial eel fishermen were fighting their own battle, against electric fishing.
More eels being processed at the Invercargill plant had been found with bent backs, evidence they were being accidentally injured during electric fishing surveys. There were also scientific papers to support that, he said.By Laura Mills of the Greymouth Star