MPI fisheries officers and DOC rangers were waiting at the boat ramp to apprehend the offenders.
"The suspects had a large number of fish - they'd clearly been having a good day," said DOC Kapiti Wellington operations manager Jack Mace.
"But this was a blatantly illegal act in a well-observed marine reserve on Wellington's doorstep.
"The community's vigilance has paid off and the witness deserves full credit for this outcome."
Following investigations, the perpetrators could face charges under the Marine Reserves Act and Fisheries Act. Penalties for taking marine life from a marine reserve include up to three months in prison, fines of up to $10,000 and possible forfeiture of boats and fishing equipment.
"This is a clear reminder that offenders who flout the marine reserve rules will be caught," said Mace.
Friends of Taputeranga Marine Reserve are a volunteer group who operate continual monitoring of the reserve through their Coastwatch service where residents patrol and respond to suspicious activity in collaboration with DOC.
The 854ha Taputeranga Marine Reserve extends approximately 2.3 km off Wellington's south coast, covering the area around Houghton, Island and Owhiro Bays.
Large yellow markers denote its east and west boundaries for vessels at sea, and shore-based signs advise people of the rules.
Anyone who spots suspicious activity in a marine reserve including taking of fish or shellfish should call 0800 DOC HOT (0800 362 468).