Hector's and Māui dolphin incident database
IntroductionWe maintain a database of incidents based on reported events. Incidents include dead or stranded Hector’s and Māui dolphins and those caught by fishers.
The data is updated and released every quarter.
Reports may be of dolphins:
- alive stranded on the beach
- injured but alive at sea
- washed up dead on beach
- found floating dead at sea or
- caught during commercial or recreational fishing – bycatch, may be dead or released alive.
Spreadsheet of Hector's and Māui dolphin incidents: 1921 to 30 April 2023 (XLS, 838K)
The data is provided in two tabs, one for event information and one for individual information. With the 'individuals' tab, data is displayed as one row per individual. Some events may include multiple individuals, use the 'MarMam observation ID num' to identify individuals involved in the same event. Event information will be the same for each individual in that event.
For more information about the data, see the user information guide (PDF, 472K)
Quarterly incident update reports - includes pathology reports
Quarterly updates are posted about Māui and Hector's dolphin incidents in early May, August, November and February each year.
- Individual updates are current as at the date of publication.
- Results that are pending at that time will be updated as they're received.
- Incidents are now grouped per year but will still be updated every quarter.
Data on observed captures will generally be reported here only in the quarterly report after the quarter that the incident occurred in. This is to align reporting and maintain the integrity of government fishery observer programmes.
Where reports come from
Our work to learn more about the threats to these dolphins relies on prompt reporting of dead dolphins by members of the public. The database is biased to areas visited frequently by people, so tends to have more reports from areas that have higher visitor numbers. The database also relies on reports from fishing vessels that may have caught dolphins during their fishing activity – this is a legal requirement.
The earliest record in the database is from 1921. Some reports are historical records from museums or universities, but much of the information in the database is from reports investigated by DOC.
Currently, investigation of all Māui and Hector’s dolphin mortality includes:
- photographing the dolphin as it was found
- taking a genetic sample and measurements
- necropsy (the animal equivalent of an autopsy or post-mortem), where possible, by specially trained veterinarians to determine the cause of death and collect additional scientific samples and information.
What the database contains
The database contains a variety of information about each dolphin, including its sex, size, where it was found, any background information, where relevant, about the incident and information collected during the necropsy.
In some cases, dolphins may not have been assessed for a cause of death. The carcass may have been too decomposed to find out how the dolphin died, or the body was lost before it could be retrieved. In some cases, there may be clear evidence for a dolphin’s cause of death (for example, a specific wound), although in others there may be no clear evidence at all.
The database also contains results from any DNA analysis done. This analysis can provide genetic sex and haplotype information and is required to definitively determine between the Hector's and Māui dolphin subspecies. Haplotypes are portions of DNA that are only passed on by females, so each dolphin has the same haplotype as its mother. Haplotypes are assigned letters of the alphabet. There are 20 haplotypes in Hector's dolphins, and one that is unique to Māui dolphins (G).
Trainee Ranger Guy Brannigan measures a dead Hectors calf washed ashore at Warrington Beach near Dunedin in December 2012