Maui's Dolphin Research

This dataset covers several pieces of work, as described below: Russell, 2008: The objective of this report is to discuss recent (August 2002 – December 2007) sightings of Maui’s dolphin along the west coast of the North Island and add to the information presented in previous reports to the Ministry of Fisheries (Russell 2002a & Russell 2002b). The focus of the report is on harbour sightings and sighting reports near or outside the current known range of this sub-species. Scali, 2008: This objective of this work is to quantify the occurrence of Maui’s dolphins in the Manukau harbour and other North Island west coast harbours, including Kaipara, Raglan and Kawhia harbours Purpose: To gain a better understanding of the Maui's dolphin population and distribution. This dataset covers a number of pieces of work related to Maui's Dolphin

Conclusions from Russell (2008): In the five year period this report covers, Maui’s dolphins have been sighted throughout the range of what is considered their known distribution (Baylys Beach to Mokau). As would be expected, most sighting reports are for the summer period when coastal and harbour usage by the public are at their highest. However, the number of reports received outside the summer period is slowly increasing as regular coastal water uses (especially commercial users) become involved in the sighting network. Coastal sighting reports reflect the density distribution of the Maui’s dolphin population that previous scientific reports have indicated (Russell 1999). The majority of reports sighted Maui’s dolphins in coastal waters between Muriwai and Port Waikato. Sighting reports with precise location information (i.e. distance offshore and/or water depth) also reflected the known offshore distribution of the sub-species. There is now evidence, through validated sighting reports, that Maui’s dolphins use the harbour entrance of the Kaipara Harbour. From the information obtained, the occurrence of Maui’s in the mouth of the Kaipara Harbour is low and restricted to just the harbour mouth area. The rate of reporting of Maui’s dolphin sightings in the Manukau Harbour is similar to previously analysed periods. The information indicates that although the dolphins utilise the outer harbour (up to the boundary of the closed area) as part of their home range, it is not a core area. There is limited evidence that Maui’s dolphins occasionally move further into the Manukau Harbour than the area covered by the setnet closure, however this is considered an irregular occurrence. The sighting reports provide no evidence of Maui’s dolphins entering the Raglan, Aotea or Kawhia Harbours. Both Raglan and Kawhia Harbours are well utilised by both commercial and recreational users, and other cetacean species have been regularly sighted and reported in both of these harbours. The current distribution of Maui’s dolphins has been described to range from Baylys Beach to Mokau with some use of the Manukau Harbour. The population concentration is thought to be between Muriwai and Raglan. Consideration of recent sighting data confirms that the majority of the sightings continue to be within this range. It is however recognised that individual or small groups of dolphin occasional venture beyond the normal limits of their range (i.e. into the lower reaches of the North Taranaki Bight). If the population grows, it is likely to expand back into parts of its historical range. There appears to be a reduction in the rate of sightings of Maui’s dolphin south of Raglan. The reason for this is unknown, but may reflect a further contraction of the range the sub-species is known to be resident in. Historically the contraction of the populations range has been more severe at the southern extreme of their distribution (Russell 1999). It is recommended that the collection of more robust, scientific data on the harbour usage of Maui’s dolphin, either intensive, long-term, boat-based surveys or satellite tagging of Maui’s dolphins, be considered. For additional information on long-shore movements of Maui’s dolphins, again, it is recommended that satellite tagging of individuals be considered. These are tried and proven methods for the collection of this type of data for small cetacean species. Continuation of a validated sighting database is also recommended.

Coastal waters of North Island - predominantely West Coast.

2007 onwards

Various, as discussed in reports.

Varied.

Reports available through Department of Conservation

Past Studies