Maui's dolphin surveys

Since the establishment of the set net closure between Maunganui Bluff and Pariokariwa Point in 2008, the Department of Conservation (DOC) has continued to collect information regarding the current distribution of Maui's dolphins. 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.

Maui's dolphins

The recent distribution information has been collected from vessel surveys, observations, and aerial surveys (both fixed wing and helicopter). Also included in the information provided are the sightings of Maui's dolphins that have been reported to DOC and Ministry of Fisheries offices. World Wildlife Fund (WWF) also holds records of sightings that have been reported to their Maui's dolphin hotline.

Surveys

DOC has undertaken a number of different opportunistic and systematic surveys since 2006 including 'alongshore surveys' (up and down the coast) and 'offshore surveys'.

Alongshore surveys

Annual alongshore surveys from 2006 to 2009 were used to find out more about how far Maui's dolphins move up and down the coastline. Boat and plane surveys for other purposes over this period, and also in 2010, have also contributed to our knowledge of the dolphins' distribution.

Key findings:

• These alongshore surveys concentrated on an area as far north as Bayleys Beach in Northland and as far south as New Plymouth.
• The southern-most survey sighting was during 2009 at Tirua Point, about 16 nautical miles (nm) south of Kawhia Harbour. The northern-most aerial sighting was about 1nm off Piha beach, but a boat survey in 2010 recorded Maui's dolphins 4nm south of the Kaipara Harbour mouth.

Offshore aerial surveys

Maui's dolphin

Systematic annual offshore surveys were completed from 2006 to 2009. Boat-based surveys were carried out in the summers of 2010 and 2011.

Key findings:

2010-2011

Boat-based surveys undertaken. See Maui's 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 2nm from shore.
• The furthest offshore sighting was recorded at 6.18nm.
• 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 nine sightings made.
• Five sightings were within 1nm of the shore and three were between 3 and 4nm from shore.
• The furthest offshore sighting was recorded at 4.3nm 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 3nm of shore.
• One sighting was recorded 4.05nm offshore, near Carter's Beach.
• One sighting was from north of the Manukau Harbour, approximately 1.2nm 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, with possible sightings up to 10nm offshore.