Sustainable Levels of Human Impact for Hector’s Dolphin

Hector’s dolphin is endemic to New Zealand, and listed as endangered on the IUCN Red List and equivalent New Zealand list of threatened species. The main threat to the species is entanglement in fishing gear, in particular gillnets. The Potential Biological Removal (PBR) method developed by the US National Marine Fisheries Service is a commonly used standard for determining a level of bycatch for marine mammal populations which, if exceeded, is likely to cause population decline. For Hector’s dolphin, PBRs are less than one individual per year for most populations and the total for the whole species is less than 10 per year. Current estimated bycatch is on the order of 10-35 times higher than these PBRs. This is consistent with several Population Viability Analyses indicating that under current management Hector’s dolphin populations are declining rapidly.