To protect Māui and Hector's dolphins from bycatch, the government is proposing to significantly expand areas of ocean around New Zealand free of set nets and trawl nets.

Photo: Gary Webber/ 123rf

Conservation Minister Eugenie Sage and Fisheries Minister Stuart Nash released proposals for consultation for a revised Threat Management Plan for the dolphins.

The discussion document includes suggestions to extend the Banks Peninsula Marine Mammal Sanctuary north to Kaikōura, south to Timaru, and offshore to 20 nautical miles, as well as extending the boundaries of the West Coast North Island Marine Mammal Sanctuary south to Wellington.

"These precious dolphins are New Zealand taonga. We need to act now to ensure their populations increase and both species thrive," Ms Sage said.

"Māui dolphins are nationally critical with only an estimated 63 dolphins remaining. Hector's dolphins are nationally vulnerable with about 15,000 in New Zealand waters."

Photo: DOC

"The proposals include options for a significant expansion of the areas of ocean free of set nets and trawl nets to protect dolphins from the risk of bycatch in fishing nets," Ms Sage said.

Mr Nash said the document recognised the need to balance protection the dolphins against the impacts on peoples' livelihoods.

"The scientific risk assessment has been through multiple rounds of peer review including by an international panel of experts and it draws on a range of new information," he said.

"Combining the latest data and expertise means this is the most comprehensive and robust assessment to date of the risks to the dolphins."

The discussion document identifies other threats that need to be dealt with to protect the dolphins; including toxoplasmosis and sub-lethal threats such as seismic surveys and seabed mining.

Seismic surveys use compressed air to create an explosive sound that travels to the bottom of the ocean, where its echo gives a clue about what minerals lie beneath. Environmentalists have long argued that these are harmful to marine mammals, though the oil industry has rejected this.

Toxoplasmosis, a disease that can kill dolphins and other marine mammals, is caused by micro-organisms that travel to the ocean via cat faeces.

Recent research by NIWA has indicated that toxoplasmosis is a greater risk to dolphins than fishing.

The proposals to deal with this included "enhancing education for cat owners", the ministers said.

A moratorium on commercial tourism permits targeting Māui dolphins is also proposed to minimise the disturbance to the dolphins from boats.

Another proposal was to improve riparian environments, such as wetlands, that filter out harmful organisms before they move from the land into the ocean.

"We know people are passionate about marine mammals and there are a wide range of views out there about the best way to protect them," Ms Sage said.

"I encourage everyone to share their thoughts and make a difference."

Read the full report: Protecting Hectors and Māui Dolphins