The proportion of Hector’s and Māui’s dolphin deaths relating to set nets and fishing gear are compared with assessed incidents of Hector’s and Māui’s dolphins being found dead. The data were retrieved from the Department of Conservation Incident Database for 1921–2008 (Department of Conservation, 2013).
The number of dolphins known to have died after becoming entangled in fishing gear is derived by adding deaths recorded against fishing gear (‘cray pot’, ‘recreational set net’, ‘commercial set net’, ‘unknown set net’, and ‘trawl net’) in the ‘known entanglement’ category.
The proportions are determined against the number of assessed deaths (all recorded deaths, except those in the ‘not determinable’, ‘not available’, and ‘not assessed’ categories). Overall, 58 percent of recorded Hector’s and Māui’s dolphin deaths were assessed for a cause of death.
Limitations of the data
The accuracy of the data source is of medium quality.
The Hector’s and Māui’s dolphins are subspecies of the small dolphin Cephalorhynchus hectori. They are endemic to New Zealand (not found anywhere else). The Hector’s dolphin is classified as nationally endangered, while the Māui’s dolphin is nationally critical. This dataset relates to the "Bycatch of protected species: Hector’s and Māui’s dolphin" measure on the Environmental Indicators, Te taiao Aotearoa website.
Purpose of collection
Reporting incidental dolphin deaths from fishing helps us understand the pressures our protected marine species face from fishing.