DOC’s recent work with Maui’s dolphin

Surveys
Sightings

Since the establishment of the set net closure between Maunganui Bluff and Pariokariwa Point in 2002, the Department of Conservation 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.

The recent distribution information has been collected from vessel surveys and observations, plane surveys and also by 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 and also reported by the public through the WWF Maui’s dolphin hotline. 

The Department also administers a database of reported Hector’s and Maui’s dolphin mortalities. In the past year this database has been updated and a summary is provided below.

You can view this information by reading the summary of the surveys and also by viewing the maps to see where these rare dolphins have been sighted. 

Surveys

DOC undertook a number of different opportunistic and systematic surveys during 2006, 2007 and 2008, including alongshore (up and down the coast) and offshore (unpublished information).

Alongshore surveys

Alongshore Surveys in 2006, 2007 and 2008 were used to find out more about how far Maui’s dolphins move up and down the coastline.

Key findings:

• These surveys concentrated on an area as far north as Muriwai and at least as far south as Raglan.
• Alongshore sightings mostly come from the 2006 and 2007 surveys with 5 helicopter sightings, 14 plane sightings and 6 boat sightings.
• Most sightings (16 out of 25) were between the Manukau Harbour and the Waikato river mouth.
• The southern most survey sighting during 2006 and 2007 was 14km north of Carters Beach and the northern most sighting was 1.7km off Piha beach. 

Offshore aerial surveys

Systematic offshore surveys (unpublished information) were completed during 2006 and 2007 using fixed wing aircraft and a standard method for aerial surveys. A summary and maps of the findings are provided. 

2006

• The 2006 surveys show a less clear pattern in terms of reliable offshore sightings.
• Sightings were widely distributed between Muriwai and Carter’s Beach, with possible sightings up to 10 nautical miles (nm) offshore.
• The most reliable sighting offshore during the survey was 7 miles offshore from Muriwai Beach.

2007

• There were high concentrations of sightings between the Manukau Harbour and the Waikato River.
• 9 sightings were south of the Waikato River.
• Most sightings (11 out of 13) were made within 3 nautical miles of shore.
• One sighting was recorded 4.05 miles offshore, near Carter’s Beach.
• 1 sighting was from north of the Manukau harbour, approximately 2.2 km offshore of Muriwai Beach.

Sightings

Recently the Department of Conservation has been collating the known Maui’s dolphin sightings information. This information comes from a number of different sources including research sightings and public sightings (reported to DOC offices or the WWF Maui dolphin hotline). Also, DOC and Ministry of Fisheries staff have reported opportunistic sightings. Some sightings have more reliability than others within the database. However, the overall pattern of sightings information is similar to the survey information. It is important to remember that public sightings will generally be clustered around areas of human activity. For the purposes of this update, reports with GPS locations are mapped separately from sightings with verbal and general locations.

Key points of interest:

• There have been 497 reported sightings of Maui’s dolphins on the West Coast of the North Island from historical records till 2008.
• Sightings range from Kawhia Harbour to New Plymouth area.
• Most sightings within the Manukau are clustered around the outer region of the harbour (note that this area has the highest urban population).
• 4 of the public sightings occur between around 8.75 and 14 miles offshore.
• 54 sightings were provided with the general location of the sighting; 3 had only the general region reported; 209 were provided with GPS locations and 231 had a verbal description of the location.
• Group sizes range from 1 to 15 dolphins

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