New Zealand's endangered Hector's dolphin population could recover if protection measures were extended to 100m deep throughout its habitat, according to a new University of Otago review.
Associate professor of zoology Liz Slooten studied the effectiveness of area-based management to reduce the number of dolphins being caught during fishing and found it could succeed if certain key criteria are met.
They include the protected area being large enough and in the right location, key threats being effectively managed and preventing new threats, such as marine mining, tidal energy generation and pollution, being added.
The review is published in the international journal Endangered Species Research.
Associate Professor Slooten said a long-term study of Banks Peninsula marine mammal sanctuary shows that protected areas, where gillnets and trawling are banned, can work.
"At Banks Peninsula, survival rates have increased by 5.4 per cent since the sanctuary's creation in 1988, and the previously rapid population decline has slowed substantially.
"However, nationwide, Hector's dolphins continue to slide towards extinction, mainly due to continuing bycatch in areas with few or no dolphin protection measures," she says.
Examples include the lack of protection off the South Island's north coasts, and that Hector's dolphins range to six nautical miles off the west coast of the South Island, but protection only extends to two nautical miles for three months of the year.
Several scientific organisations, including the Scientific Committee of the International Whaling Commission and the International Union for Conservation of Nature have recommended that protection be extended to 100 metres deep in Hector's dolphin habitats.
"Most Hector's do not range beyond waters of this depth. Extending protection out to this mark would largely eliminate the currently unsustainable level of bycatch."
Associate Professor Slooten said if that measure was adopted dolphin populations could recover to around 15,000 within 40 years.
There are an estimated 7270 South Island Hector's dolphins and as few as 55 North Island Hector's dolphin, which is also known as Maui's dolphin.