Hector's dolphin risk assessments: old and new analyses show consistent results

Abstract

We review results of previous research and present new estimates of Hector's dolphin (Cephalorhynchus hectori) bycatch. Before 2008, an estimated total of 110–150 individuals were caught annually, with 35–46 caught off the east coast South Island (ECSI). We estimate that 23 Hector's dolphins were caught off ECSI during 1 May 2009–30 April 2010 (CV 0.21) based on fisheries observer data. This confirms results from risk analyses, indicating continued overlap between dolphins and fisheries. There is a high level of consistency among different risk assessments, despite large differences in model structure and parameterization. For example, without fisheries mortality Hector's dolphin populations could recover from 7873 (CV 0.16) today to around 15,000 individuals in the next 50 years (Schaefer model estimate 15,411; CV 0.16; Bayesian model 14,650; range 12,313–19,250). All risk analyses indicate that populations have declined substantially due to fisheries mortality and recovery is unlikely under the current protection measures.