Hector's Dolphin - Population and Distribution

Population and Distribution

Hector's dolphins are endemic to the coastal regions of New Zealand. The species has a patchy distribution around the entire South Island, although there are only very occasional sightings in the deep waters of Fiordland. The centres of distribution are on the west coast between Kahurangi Point (41˚S) and Jacksons Bay (44˚S) and on the east coast around Banks Peninsula (43˚S-44˚S). Maui’s dolphin is found only on the west coast of New Zealand’s North Island between 36˚S and 40˚S, with the majority of animals in the central portion of this range between the Manukau and Raglan Harbours.

Abundance has been estimated from a series of five line-transect surveys between 1998 and 2004. The abundance estimate for South Island Hector’s dolphin is 7270 (CV = 16%). Current population size is estimated to be 27% of the abundance in 1970 before significant human impacts occurred.

The species has a preference for shallow, coastal waters less than 100 m deep. This means they are most commonly seen close to shore, although in shallow regions they have been sighted up to 34 km from the coast. In some areas, there is a pronounced seasonal difference in distribution, with dolphins being sighted further offshore and in deeper water in winter, presumably in response to movements of their prey species.