Maui's Dolphin Aerial Surveys - West Coast

A number of surveys were conducted between 2008-2009, as described below: A series of alongshore aerial surveys were carried out in 2008 on the west coast of the North Island to examine the distribution of Maui’s dolphin (Cephalorhynchus hectori maui) in relation to the southern boundary of the current protected area. Thirteen surveys were carried out between the Manukau Harbour in the north and Cape Egmont in the south. During these surveys 23 groups of Maui’s dolphins were sighted between the Manukau Heads and just south of the Mokau River. The southernmost sighting was approximately 10.4 n.mi north of the southern boundary of the protected area. Aerial survey flights were undertaken and conducted in January, February and March 2009 along the west coast of the North Island of New Zealand between Port Waikato and Sugar Loaf rocks, for the purpose of gathering abundance data on the alongshore distribution of Maui’s dolphins in relation to the southern boundary of the current protected area. Sightings of other cetacean species were also to be recorded. The Department also conducted Maui’s winter offshore aerial surveys in October 2007, May 2008 and June-July 2009. The aim was to identify, detect and determine individual Maui’s present during the winter season along the North West coast of the North Island. The survey covered the zone between the shore and 10 nautical miles (nm) off the coast. Alongshore aerial surveys were also undertaken in 2012 and 2013. Boat-based surveys were completed during summers 2010 - 2013.   Alongshore surveys from 2006 - 2013 are used to find out more about how far Maui dolphin move up and down the coastline, whereas offshore surveys tell us about how far offshore the dolphins range.

Data on aerial sightings of Maui Dolphin and other cetacean species on the West Coast of the North Island.

West Coast North Island

2007-2009

The survey platform was a Cessna 172; a single engine, 4-seater, high-wing aircraft. Transects were flown at a constant altitude of 500ft (152 m) at a speed of approximately 90 kts (167 km/hr). The aircraft’s track was logged throughout each flight with a Garmin GPSmap 176C and Garmin GPS II Plus, each recording a position every 10 seconds. The survey team consisted of two observers, one on each side of the aircraft in the rear seats. To reduce the risk of bias and fatigue the two observers swapped seats after each flight. The observers had a field of vision from the horizon to a downward angle of approximately 70?. Observers focussed their sighting effort as close to the trackline as possible and not above 20?. Full details of methods provided in reports. Frequency of collection: Irregular

Further, due to diving behaviour, only a proportion of the dolphins present can be expected to be at the surface and thus available for counting. (This proportion was not assessed during this survey, but was c. 50% in the surveys of Slooten et al. (2006)). While aerial surveys are useful for estimating abundance and distribution, they cannot be expected to find all the animals present. It is important to remember that a lack of sightings in any particular area does not imply that that area is not used. Rather, visual surveys are good for showing where animals are, but cannot always indicate where animals are not. Data quality: Surveys undertaken using well defined and consistent methods.

Reports available in electronic form from Department of Conservation

Understanding the geographic distribution of the critically endangered Maui dolphin to guide fishing restrictions and other management actions.

Data set available from Department of Conservation. Many publications available online, e.g. see link below.

Ongoing