A western Bay blackmarket ring was so large and sophisticated it threatened the region's snapper fishery and the country's Quota Management System, a senior Government official says.
Fisheries officers used every tool in their armoury to smash the ring, the Bay of Plenty Times Weekend can reveal.
Seven people were involved in the illegal disposal of at least 13 tonnes of fish - mainly 12 tonnes of snapper.
Brendon Mikkelsen, Ministry of Primary Industries' Waikato/Bay of Plenty compliance manager, said it was a case of "not only following the fish but following the money".
This week the last member of the ring, Tauranga businessman Joung Oh (James Lee), was found guilty for his role in the illegal enterprise.
Lee, who was caught selling more than 9000kg of fish and made about $52,000 from illegal sales during a two-month period, will be sentenced next month.
The others prosecuted include Wayne Howell, the skipper of Tauranga-based trawler Newfish II, registered to Lee's company ECZIW - now in liquidation.
Also involved were Western Bay Seafoods truck-driver Hira Cyril Noble and takeaway-shop owner Lay Queen Lim - both of Tauranga, Hamilton Seafoods operator Jason Lionel Abbott, and Auckland fish retailer Tuan Tran. They have already been sentenced.
The Bay of Plenty Times Weekend can reveal the ring made a profit of at least $78,000 over an eight-week period, some of which was laundered through TAB accounts.
The prosecutions were the culmination of more than two years of work. Operation Waterfowl, which involved at least a dozen fishery officers, was launched in late 2011 after an anonymous tip to the ministry's 0800 4 Poacher line.
A team tracked the Newfish II fishing on the Mount/Papamoa coast, watched bins of fish unloaded on to trucks, which were followed to fish retailers in Tauranga, Hamilton and South Auckland and a takeaway in Tauranga.
Fisheries officers also searched homes and businesses and seized hundreds of pages of documents, bins of fish, and cash.
"We also exercised our powers to check bank accounts, bank statements and went through other paper work including TAB account records. It took a significant amount of analytical work comparing all those records with fishing catch returns and declared fish."
Two trucks and the Newfish II trawler seized were permanently confiscated.
Mr Mikkelsen said the offenders were effectively operating an illegal shopfront, with up to 50 per cent of the unloaded catch destined for the blackmarket, and not declared in any catch returns.
Some of the snapper was sold on the black-market at $6kg, while if sold at Auckland Fish Market the buyer would have to pay $8-$9kg, and the fisher would have had to pay $6kg back to the ministry under the quota management system rules.
Mr Mikkelsen said it was satisfying to put the ring out of business.
"The sheer scale of this offending detected in just eight weeks is important, and the fact that we detected offenders in every link of the fish supply chain, and the impact on our future fisheries environment is of major concern.
"It is definitely one of the biggest blackmarket rings busted in this region since Operation Buster which went down in the 1990s."
That involved 80 tonnes of illegal sales.
"Clearly these prosecutions don't fully represent the extent of the harm caused to our future fishing stocks."
Mr Mikkelsen said the offenders' actions had threatened the integrity of the Quota Management System.
"It gave them an unfair advantage over law-abiding operators and threatened fish stocks such as snapper fishery in the Bay of Plenty.
"They have also threatened to sabotage the best tool yet devised to enable New Zealand and the global community to protect and enhance fish stocks," he said.
Primary Industries Minister Nathan Guy said the offenders pillaged resources that belonged to all New Zealanders and put the viability of fish stocks at risk.
"I want to congratulate MPI for bringing this case before the courts. It sends a strong message to other blackmarket operators they will be caught, and they will be punished."
The minister announced a range of measures in September to increase monitoring of commercial fishers in the Snapper 1 area.
This includes mandatory observers or cameras on 25 per cent of the snapper 1 trawl fleets by tomorrow, expanding to 50 per cent of the fleet by October 1 next year, then all of the fleet by October 1, 2015.
Mr Guy said work is also under way to introduce mandatory vessel monitoring systems on all commercial vessels by October 1 next year.
A $7 million scientific tagging survey would also be introduced.
Mr Mikkelsen said there was also an unrelated prosecution case going through the Tauranga District Court which related to the alleged misreporting of almost 10 tonnes of fish.