"They are commercial-free areas that were set up by our elders in the 1940s," he said.
"They could see the problem with trawlers coming all the way in - it was the first time anything like that had been put in place."
He said the main advantage of mataitai status was quick action to preserve species.
"Usually you have to apply through a whole lot of channels to get a ban put in place, which can take about three years."
Under the mataitai system, the Minister for Primary Industries could have one in place within six months of a request from reserve guardians.
Anyone with property on a reserve's beach, Maori or Pakeha, could have a say in the reserve's management, Mr Cooper said.
Mataitai status affects customary harvesting - permit writers can give permission to harvest only in their own reserve and must report authorisations to the ministry.
The Horokaka Mataitai Reserve covers approximately 4.1sq km and 3.4km of coastline.
The Toka Tamure Mataitai Reserve covers approximately 2.9sq km and 4.5km of coastline.
Te Hoe Mataitai Reserve covers approximately 14.5sq km and 12km of coastline.
Two new South Island mataitai reserves have also been announced.
Waihao Mataitai Reserve is located northeast of the Waimate township, South Canterbury and Okarito Lagoon. Mataitai Reserve is located north of Franz Josef on the west coast of the South Island.
There are currently 29 mataitai reserves, including the five new reserves.