Māui dolphin location surveys

Since the expansion of the set net closure between Maunganui Bluff and Pariokariwa Point in 2008, DOC has continued to collect information regarding the current distribution of Māui dolphins (with the support of the Ministry for Primary Industries). This includes how far they live up and down the west coast of the North Island and also how far they range offshore.

We have also looked into their utilisation of the North Island west coast harbours. It is important to have a firm idea of where the dolphins range so that we can effectively manage both fishing and non-fishing threats within the entire range of the dolphins.

Surveys

DOC has undertaken a number of different opportunistic and systematic surveys since 2006 including acoustic surveys, ‘alongshore surveys’ (up and down the coast) and ‘offshore surveys’ (parallel transects). These include:

• photo identification surveys
• acoustic surveys between 2016 and 2019
• systematic annual offshore surveys completed from 2006 to 2009
• alongshore aerial surveys from 2012 to 2013
• boat-based surveys during summers from 2010 to 2013.  

Alongshore surveys are used to find out more about how far Māui dolphin move up and down the coastline, whereas offshore surveys tell us about how far offshore the dolphins range.

Key findings

• These alongshore surveys have covered an area as far north as Baylys Beach in Northland and as far south as Hāwera.
• The southern-most survey sighting was during 2009 at Tirua Point, about 16 nautical miles (nm) south of Kawhia Harbour. The northern-most sightings were just south of the Kaipara Harbour mouth.
• Offshore sightings of Māui dolphins have been confirmed between 4 and 7 nm offshore, but acoustic detections have been as far offshore at 9.8 nm.

Photo identification surveys

These surveys use photo identification of individual dolphins through dorsal fin nicks. Although Hector’s dolphins have a low rate of distinctive marks (eg only 10–15% of dolphins), analyses show that some Māui dolphins are distinctive, making it possible to identify and track individuals over time.

Māui dolphin photo-identification using artificial intelligence – Final report – 2022 (PDF, 1,170K)

Progress report on photo identification surveys of Māui dolphins in 2019 (PDF, 887K)

Vessel surveys and photo identification of Māui dolphins in 2017 (PDF, 1,974K)

Acoustic survey 2016 – 2019

Acoustic monitoring of Cephalorhynchus hectori off the West Coast North Island New Zealand, Nelson and Radford, 2019 (PDF, 1,149K)

• New research using acoustic underwater monitoring devices has confirmed that Hector’s or Māui dolphins are often present in the Taranaki region.
• DOC worked with the University of Auckland to deploy and analyse acoustic devices placed offshore from Hamilton’s Gap just outside Manukau Harbour, and at various points along the coast of Taranaki and Whanganui between November 2016 and April 2019.
• The furthest offshore detection of a Māui or Hector’s dolphin was at 18.2 km (or 9.8 nm) offshore from Hamilton’s Gap, just outside Manukau Harbour.
• The devices, known as C-PODs, detect click trains in the high frequency that Māui and Hector’s dolphins emit when foraging.
• The difference in vocalisation allows scientists to reliably distinguish them from other species of dolphin, however, Hector’s and Māui dolphins are the same species and it is not yet possible to distinguish between the subspecies through their vocalisation.

Summary by season

2012 – 2013 

Boat-based surveys undertaken 

Awakino to Oeo boat survey map (PDF, 496K)

Taranaki boat surveys summary report (PDF, 77K)

• Six separate boat surveys were undertaken between Awakino and Oeo from December 2012 to March 2013:
  • New Plymouth to Awakino (4 trips)
  • New Plymouth to Oeo (1 trip)
  • New Plymouth to Opunake (1 trip)
• A total of 836 km, or 464.5 nm was surveyed with a total of 26 hours and 2 minutes of on-effort observation.
• No Hector’s/Māui dolphin were sighted.

Alongshore aerial surveys undertaken

Alongshore aerial survey map (PDF, 508K)

Taranaki aerial surveys summary report (PDF, 77K) 

• Five separate alongshore aerial surveys were undertaken using a fixed-wing aircraft. Surveys departed New Plymouth Airport north to Awakino, returning to the airport to re-fuel. The aircraft then flew south to Hāwera, again returning to New Plymouth Airport.
• The aircraft flew within approximately 1 and 2 nm from shore.
• A total of 1811 km, or 1006 nm, was surveyed with a total of 12 hours and 6 minutes of on-effort observation.
• No Hector’s/Māui dolphin were sighted.

South Kaipara Head to Mōkau

Auckland boat surveys summary report (PDF, 104K)

• Three separate boat-based surveys were conducted between South Kaipara Head and Mōkau during March and April 2012:
  • Raglan to Manukau
  • Raglan to Mōkau
  • Manukau to Kaipara
• A total of 657.4 km, or 355 nm, was surveyed with a total of 27 hours 50 minutes of on-effort observation.
• Thirteen Māui dolphin groups were sighted. 28 were recorded as adults, 12 as juveniles and 2 as calves. On analysis of body markings and dorsal fin photographs, it was confirmed that one adult Māui dolphin had been resighted, reducing the actual numbers of adults encountered to 27.
• The northern most Māui dolphin was observed approximately 3.7 nm south of Kaipara harbour mouth.
• The southern most sighting was 9 nm south of Manukau harbour mouth.
• Māui dolphin were observed in the depth range of 5.5–12.2 m of water.
• The Māui population encountered when compared to a comparable survey in 2012 provides the same numbers of adults (27) and juveniles (12), but with the addition of 2 calves (as none were observed in 2012).

2011 – 2012 

Tirua Point to Opunake

• Seven separate boat surveys were undertaken between Tirua Point and Opunake from October 2011 to April 2012:
  • New Plymouth to Tirua Point, return (3 trips)
  • Awakino to New Plymouth (2 trips)
  • New Plymouth to Opunake, return (2 trips)
  • No Hector’s/Māui were sighted.

Woody Head, Raglan to South Manukau Heads, Auckland

• One boat-based survey was conducted between Woody Head and Manukau Heads during March 2012.
• A total of 235 km, or 126.8 nm, was surveyed with a total of 10 hours 36 minutes of on-effort observation.
• Twelve Māui dolphin groups were sighted. Twenty-seven were recorded as adults, 12 as juveniles and no calves were recorded.
• The northern most Māui dolphin was observed approximately 5 km south of Manukau Harbour mouth entrance.
• The southern most sighting was 8km south of Raglan harbour mouth entrance near Woody Head.
• Māui dolphin were observed in the depth range of 9–14 m of water.

2010 – 2011

Boat-based surveys undertaken. See Māui dolphin abundance estimate.

2009 – offshore

• This survey covered the area from Bayleys Beach to Kawhia Harbour.
• There were 12 sightings made.
• Nine sightings were within 1nm of the shore and two were between approximately 1 and 2 nm from shore.
• The furthest offshore sighting was recorded at 6.18 nm.
• The northern-most sighting was just south of the Kaipara Harbour mouth and the southern-most was midway between the Manukau Harbour and the Waikato River mouth.

2008 – offshore

• This survey covered the area from the Kaipara Harbour to Raglan Harbour.
• There were 9 sightings made.
• Five sightings were within 1nm of the shore and 3 were between 3 and 4 nm from shore.
• The furthest offshore sighting was recorded at 4.3 nm from shore.
• The northern-most sighting was off the Kaipara Harbour mouth and the southern-most was midway between Raglan and the Manukau Harbour.

2007 – offshore

• This survey covered the area from Muriwai to Carters Beach, just north of Raglan.
• There were high concentrations of sightings between the Manukau Harbour and the Waikato River.
• Nine sightings were south of the Waikato River.
• Most sightings (11 out of 13) were made within 3 nm of shore.
• One sighting was recorded 4.05 nm offshore, near Carter's Beach.
• One sighting was from north of the Manukau Harbour, approximately 1.2 nm offshore of Muriwai Beach.

2006 – offshore

• This survey covered the area from Muriwai to Carters Beach, just north of Raglan.
• Sightings were widely distributed between Muriwai and Carter’s Beach.

Related links

• Hectors dolphin incident database records reports about Māui dolphin
• Distribution of Māui dolphin: 2000–2009 (PDF, 2,569K) This report synthesises surveys and sighting records of Māui dolphin.