Multi‐event modeling of Hector's dolphin ( Cephalorhynchus hectori ) fecundity using four decades of monitoring: Implications for current management of bycatch

Prediction of future population trajectories is vital in the management of threatened species but requires accurate estimates of demographic rates. One such parameter is fecundity, which is commonly expressed as the number of offspring produced per female per year. The endangered Hector's dolphin ( Cephalorhynchus hectori ) is Aotearoa New Zealand's only endemic cetacean and is threatened by bycatch from inshore trawl and gillnet fisheries. Here, we take advantage of 40 years of continued photo‐identification effort at Banks Peninsula to construct a Bayesian open‐population multi‐event capture–recapture model. We estimated fecundity for Hector's dolphins at 0.29 (95% credible interval [CI]: 0.22–0.39) which corresponds to an average calving frequency of one calf every 3.4 years (95% CI: 2.5–4.7 years). This new estimate is substantially lower and more precise than the previous estimate of fecundity for Hector's dolphins (e.g., 0.409, 95% CI: 0.267–0.635), but is based on a larger dataset, and aligns closely with estimates from other dolphin species. This updated estimate of fecundity indicates a lower capacity for population growth and reduced resilience to anthropogenic threats, including bycatch in fisheries.