The ministry declined to identify the two men beyond saying they were from Northland.
Mr Rudsdale said it was important to know the difference between toheroa and the more common tuatua, which were much more prolific so were not subject to the same gathering ban.
Toheroa shells were more brittle and slightly rounder than tuatua, with a slight lump at the base. Tuatua shells were slightly glossy in comparison to toheroa, and had a square, flat base.
A simple test was to sit the shellfish on its base on the sand with the sharp end standing up. A tuatua should stay standing, balanced on the flat base, while the toheroa should fall over.
The two species could be the same size and colour, depending on their age, but toheroa would eventually grow much bigger and would have a darker shell.
"We'll be taking a zero tolerance approach to any taking of toheroa in this area," Mr Rudsdale said.
"Fisheries officers will be out and about patrolling regularly, as always, and I understand locals will be stepping up their efforts to patrol the beach as well.
"The penalty for being caught with up to 50 toheroa, or even disturbing them, is a fine of up to $500. If you are caught with more than 50 you face prosecution and a maximum fine of $20,000.
"There will be no excuse for any offending."