5 Aug 2016

Twice as many Hector's dolphins as previously thought

5:40 am on 5 August 2016

A three-year study has revealed there could be twice as many endangered Hector's dolphins in New Zealand waters as previously thought.

Hector's dolphins off Banks Peninsula.

Hector's dolphins off Banks Peninsula. Photo: AFP

The Cawthron Institute led the largest marine aerial survey conducted in the country which showed there could be between 12,000 and 18,500 hectors dolphins.

The last published estimate, in 2003, put the population at just over 7000.

Read more on the study here.

The institute's marine mammal ecologist, Deanna Clement, said the findings were unexpected.

Hector's dolphins in coastal waters near a river mouth off the Kaikoura Penninsula.

Hector's dolphins in coastal waters near a river mouth off the Kaikoura Peninsula. Photo: AFP

"We've gone further and there's been more intensive field work this time around, so we found that there could be as many as 18,500, which is quite exciting.

"We were so surprised by the numbers we went back and we double checked, triple checked, and had multiple reviewers have a look at it."

Even more surprising was what they discovered about the dolphins' habitat, she said.

"They're much, much further offshore than we ever imagined. This animal is known to be a near shore coastal species and it was believed that the majority of them were within four nautical miles, and what we found was that they are spread out to about 20 nautical miles."

She said set nets and trawl fishing were the biggest threats to the species in New Zealand, which banned those practices up to four nautical miles offshore around most of the South Island in 2008.

"So at that point [in 2008] we were protecting the range that we thought they were in fairly well and intensely. But now with the knowledge that they're much further off shore, we're going to have to start with square one again."

"We really need to go back and then make some wise choices about where we put those restrictions."

Hector's dolphins are one of the world's rarest and smallest dolphins, weighing just 50kg.

The survey was conducted on behalf of the Ministry for Primary Industries.

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