Boaties asked to report any sightings of small, rare dolphins this summer

Boaties are encouraged to keep a lookout for rare dolphins this summer.

Maui's dolphins. Source: Supplied

The Department of Conservation said recorded sightings of Hector's and Māui dolphins would help them better understand their distribution.

Knowing where they dwelled was critical to protecting them.

Hector's and Māui were among the smallest species of dolphin in the world and were found only in New Zealand.

DOC said they were an important part of New Zealand's natural heritage, and the Māui dolphin was on the edge of extinction.

The Hector's dolphin sub-species was classified as Nationally Vulnerable, with an estimated 15,000 left primarily around New Zealand's South Island coastline.

The Māui dolphin sub-species was classified as Nationally Critical and faced a real threat of extinction, with an estimated 63 over the age of one year.

They were found off the west coast of the North Island.

These dolphins faced a number of threats including fishing, toxoplasmosis, seismic surveying, seabed mining, tourism, vessel traffic, oil spills, coastal development, pollution, sedimentation and climate change.

The small dolphins were distinguished from other species by their rounded dorsal fin - shaped like a Mickey Mouse ear.

They also have small, rounded black flippers and grow to only about 1.5 metres.

DOC technical adviser Kristina Hillock said Hector's and Māui dolphins could not be told apart by sight alone, but the Māui dolphin was only found on the west coast of the North Island and Hector's were mostly found around the South Island.

"We have had a handful of sightings off the east coast of the North Island as far north as the Coromandel Peninsula, so please be extra vigilant there," Hillock said.

DOC said people could record any sightings on a dedicated Hector's Dolphin Sightings' app, available on the App Store and Google Play.

"The app allows you to easily find your location, make a report, and upload a video or photo for verification, all in one place."

Sightings could also be reported on the DOC hotline, 0800 DOC HOT (0800 362 468) or via the DOC website.

"Any reports are useful. The more data we have, the better we can protect our marine species," Hillock said.

All sightings were verified by an independent marine mammal scientist. DOC then used the data to better understand the distribution of these rare dolphins.

"Once we can confirm that they are in a certain area, we can respond with plans for their conservation. For some of these areas we have reported sightings, but not enough to know if there is a resident population or where they've come from."

DOC was also asking for reports of stranded or dead Hector's or Māui.