The sanctuaries are at Akaroa, the Catlins Coast, in Cloudy Bay, at Stewart Island, in the Auckland Islands, and two around Kaikoura. The largest stretches 2000km down the west coast of the North Island, from Maunganui Bluff in Northland to Oakura in Taranaki.
They are set up to protect seals and dolphins as well as whales. Each restricts the specific activities that put marine mammals at risk. Set netting is banned where Maui and Hector dolphins live, for example.
Using sound waves to find out what is under the seabed (seismic surveying) is banned in some of the sanctuaries.
Forest and Bird marine advocate Anton van Helden says the restrictions vary, depending on what's needed and the legislation that sets the sanctuaries up.
"It could be anything. It's really up to whoever set it up."
Seismic surveying is especially hard on whales, he said.
"Those are actually quite full-on experiences for any whale to contend with."
He said a marine mammal sanctuary for the South Taranaki Bight is a great idea. Blue whales are known to live there year-round, local tribes have a relationship with whales and southern right whales could calve there again.
"That would be a tremendous thing to see."
The blue whales would be a long way off shore, but people could get out to see them by boat or plane.
Marine mammal sanctuaries and marine reserves have been great for the little tourist town of Akaroa, Akaroa District Promotions executive officer Hollie Hollander said.
The town has seven tourist boat operators, and people come to sea kayak, paddle board, tour the harbour and swim with dolphins.
"There are fantastic economic advantages," she said.
Destination Kaikoura general manager Glenn Ormsby agrees. His town has two marine mammal sanctuaries with seal colonies, albatross and whales nearby.
There are two major tour operators, whale watching is run by DoC and tourists can swim among hundreds of dolphins. About a million tourists come every year, and 70 per cent are from overseas.
He urged the Whanganui and South Taranaki community to go for the marine mammal sanctuary option.
"It's a real win:win for us and the marine environment, and it's also embraced by the whole town. We are proud of it, and want to look after it," he said.
