Commercial fishers are being warned "people are watching you" as operators allegedly under-reporting catches and unlawfully supplying fish face prosecution.
Tip-offs from members of the public helped lead fishery officers to a group of commercial fishing operators who were not correctly reporting catches and unlawfully supplying snapper to an Auckland business.
Last month, police and the Ministry for Primary Industries swooped on a number of locations across the Auckland and Waikato regions and seized phones, computers, six fishing vessels, a truck and $25,000 in cash.
But they also found 800kg of undocumented grey mullet and kahawai, along with over 200kg of undocumented snapper.
MPI's fisheries compliance manager, Steve Ham, said the investigation was still in its early stages, but it should be seen as a warning to others.
"Any time we have unreported fish it's always significant and it's something that we take really seriously and something we take a very dim view of, when catch isn't reported because that is the fundamental cornerstone of the whole quota management system.
"The key message here is people are watching, all the time. They're monitoring people, people are coming forward all the time with information when something is not quite right."
Eight people have been interviewed and could face prosecution, but enquiries are ongoing.
He said the operation was deemed significant enough to focus the body's resources and time into uncovering the offending and doing something about it. Forty-five officers were involved in the inquiry. The organisation has 110 officers across the country.
Ham said a focus now would be tracing where the undocumented fish had been supplied.
"It's too early to say, obviously the inquiry is ongoing as to where this fish has gone. But I think overall this is an isolated incident and we're going to put our resources into finding exactly where this fish is gone and those enquiries will be continuing over the coming months."
He urged the public to continue to use the Ministry for Primary Industries' poaching confidential hotline to help officers pursue offenders and prosecute them.
"Obviously during a busy period over summer, our officers are out and about through Christmas, but it's important that information gets to us and quiet often it could be different strands of information coming in and when you link it all together, we end up with cases such as this."