The Ministry for Primary Industries has admitted that illegal fish dumping is so widespread that if the rules were properly enforced over half of inshore fishers would go out of business.
The suggestion is made in an email between two top MPI managers, which forms part of a damning report, released on Friday, into its failure to prosecute fish dumping.
The email was sent as MPI debated whether to prosecute the illegal dumping of tonnes of fish by five of six boats it was monitoring in 2012.
In it, director of fisheries management David Turner said fish dumping was systemic and something MPI had never been able to get on top of.
"Fisheries Management can't quantify the tonnages involved but we suspect they are significant to the point that they are impacting on stocks.
"We estimate that if we found the golden bullet to stop discarding, we would probably put over half of the inshore fleet out of business overnight..."
Greenpeace New Zealand director Russel Norman said if the people in charge of enforcing the quota management system did not think it was working, then things needed to change.
"This is from the director of fisheries management in an internal email, that I suspect he thought would never be published, where he says that there is a systemic failure in the QMS (Quota Management System) which is around dumping.
"So it's a pretty direct statement from the guy who's in the position you would think within MPI who should know."
MPI's admission that dumping was significant and having an impact on fish stocks was disturbing, Dr Norman said.
"Ministry for Primary Industries always says externally, 'oh well if there is any fish dumping we know that it doesn't cause any harm because look, people are still catching enough fish out there'.
"But here is the the director of fisheries management saying in an internal email that he suspects the fish dumping is so great that it's impacting on the stocks themselves, ie that it's impacting on the sustainability of the fishery."
Not as widespread as emails claim - MPI head
Ministry for Primary Industries director-general Martyn Dunne said he did not believe the issue was as widespread as stated in the emails.
The issue of discarding and dumping was being grappled with worldwide and MPI had made its view clear that it was unnacceptable.
"If some of them [fishing companes] went out of business to make sure we no longer have this issue of discarding, then that's the way it is," he told Morning Report.
The ministry was introducing electronic monitoring that would put cameras on every boat and a trial in a snapper fishing area on the north east coast of the North Island had been successful, he said.
"The statement that they made in the email exchange ... it's not relevant going foward.
"We know there's a issue with discarding and dumping and certainly has been. Certainly in my time the moves we are making to actually correct this will ensure that we have it happen no longer."
The boats caught dumping fish in 2012 were supplying Sanford Ltd. The company accounts for a quarter of all inshore fishing in New Zealand.
Chief operating officer Greg Johansson said claims a properly enforced quota system would drive half of fishers out of business were an exaggeration.
"I think if it was that widespread, the jungle drums on the water [would] pass news around. That's why I struggle to see it would be that substantial without there being more wharf talk and more boat talk being transferred around."
He said 90 percent of fishers were conservationists and he did not believe last week's scathing report was a bad look for the industry.
"The report was into, did MPI act appropriately, not that there's a failure of the quota management system or anything else.
"It's a report into how did MPI handle the investigations and the subsequent decision making so I don't think we should condemn the whole industry based on the decisions of MPI."
The illegal dumping its suppliers were found to have engaged in was unlikely to happen again, Mr Johansson said.
"Well as soon as we were made aware of the contents of that report, we spoke to the fishers involved and we've subsequently put cameras on those vessels from that day forward and reinforced our requirement for 100 percent compliance with the law."
His company had nothing to hide and he looked forward to having cameras on board all fishing vessels in the near future, he said.