A breed of whale that was almost hunted to extinction in the 19th Century is repopulating in New Zealand waters, thanks to a remnant population from an area near the Antarctic, say scientists.

Southern right whales from a remote population in the sub- Antarctic Auckland Islands appeared to be recognizing mainland New Zealand waters in small but growing numbers to give birth and raise their calves, according to an international study.

"With the increase in numbers observed around the Auckland Islands over the last decade, we think that some individuals are rediscovering the former primary habitat around the mainland of New Zealand," said Professor Scott Baker, of the University of Auckland and Oregon State University.

The findings were based on genetic evidence from small skin samples collected from 707 whales over more than a decade, said a statement from Auckland University.

A comparison of the DNA identified just seven individual whales that had been moving from the uninhabited Auckland Islands, which lie 465 km south of New Zealand, to mainland waters.

"The seven whales that have been identified in both the Auckland Islands and the mainland are probably the first pioneers of this recolonization," said Baker.

The results supported the conclusion that the mainland New Zealand population was wiped out and that the returning whales were from the remnant sub-Antarctic population.

Researchers also confirmed genetic differences between whales around Australia and New Zealand, and gained new insights into differences in the recovery of regional populations.

"The results confirm the strong connection of right whales to regional calving grounds around Australia and New Zealand as a result of early maternal experience," said researcher Emma Carroll, of Auckland University.

"This maternal fidelity contributed to the vulnerability of these local populations, which were quickly hunted to extinction using only open boats and hand-held harpoons."

"Maternal fidelity" is passed from a mother to calf during the first year of life, as they migrate together from calving grounds to feeding grounds.

When right whales around mainland New Zealand were wiped out, maternal fidelity was thought to have been lost, slowing the return of whales to their former habitat.

The Auckland Islands are at the center of New Zealand's Auckland Islands/Motu Maha Marine Reserve, which covers an area of about 484,000 hectares in the Southern Ocean.

Surveys of the right whale population around the islands in the 1990s showed it numbered around 1,000, according to New Zealand's Department of Conversation (DOC).

The research has been published in the international journal, Marine Ecology Progress Series, by scientists from the University of Auckland, DOC, the Australian Antarctic Division, Australia's Macquarie University, the Museum of Western Australia and Oregon State University, in the United States.