Effectiveness of area-based management in reducing bycatch of the New Zealand dolphin

Abstract

The New Zealand (NZ) dolphin Cephalorhynchus hectori, also known as Hector's dolphin, is endemic and listed as Endangered by the NZ Department of Conservation and the International Union for the Conservation of Nature. The North Island population, also known as Maui's dolphin, is listed separately as Critically Endangered. The Threat Management Plan for NZ dolphins identifies bycatch in gillnet and trawl fisheries as the number one threat. Fisheries mortality has resulted in rapid population declines, with current total population size estimated at 27% of 1970 numbers. Reduced use of gillnets and trawling in NZ dolphin habitat has slowed pop- ulation declines in some areas. A long-term study in the Banks Peninsula Marine Mammal Sanc- tuary (South Island east coast) shows a significant increase in survival rates (by 5.4%) and indi- cates that the previously rapid population decline has slowed substantially. Nationwide, NZ dolphin populations are predicted to continue declining under current management. This is driven mainly by continuing bycatch in areas with few or no dolphin protection measures (e.g. South Island north and west coasts). Extending protection to the 100 m depth contour throughout NZ dolphin habitat would result in rapid population recovery. This case study shows that area- based management can work, if the protected area is large enough, in the right place, effectively manages key threats, impacts are removed rather than displaced to other areas and no new threats are added (e.g. marine mining, tidal energy generation or pollution).