Mr Mikkelsen said the minimum size for paua was 125mm and some of paua were under 90mm.
The second group of men, including one from Paengaroa, had 27 undersized paua.
"It's a very concerning start to the summer season," he said.
Two other men were picked up during a random check of their kina catch and found in possession of two undersized paua, Mr Mikkelsen said.
It was probable the two groups caught with the larger quantities of paua would face infringement notices but court prosecutions were also possible.
Mr Mikkelsen said people gathering too many and undersized paua and mussels at Newdicks Beach, Maketu had also been a problem in recent weeks. The area was often targeted by poachers.
There had been four or five shellfish prosecutions in the Tauranga District Court recently, Mr Mikkelsen said.
Fisheries officers would be stepping up compliance checks and increasing the number of checkpoints and offenders risked having their boats and vehicles permanently seized if they were used to illegally gather shellfish.
Senior Fisheries Officer Gary McAneny said the men caught in the latest sting would have walked past huge warning signs the ministry had erected on both sides of Mauao.
"Having done so, it's clear they did not give a hoot," he said.
Mr Mikkelsen praised the member of the public who tipped off the ministry and urged other members to the public to report any suspicious activity by phoning 0800 4 POACHER (or 0800 476 224).
All calls were kept strictly confidential, he said.
Snapshot of recreational gathering rules in this area
• Dredge oyster, paua and scallops must be landed in the shell and cannot be shucked or shelled seaward of the mean high water mark.
• The maximum daily limit per gatherer: 10 ordinary paua (minimum size 125mm); 25 mussels; 50 kina (sea eggs); 20 scallops (minimum size 100mm); Toheroa prohibited (unless declared an open season by MPI).
• If in doubt call the local Fisheries District Office 07 571 2820
- Source: Ministry of Primary Industries
