Hector's and Maui dolphin bycatch following 2020 management decisions
Elisabeth Slooten and Stephen Michael Dawson
In 2020, the New Zealand Minister for Primary Industries revised fisheries regulations with the goal of reducing Hector’s and Māuidolphin bycatch. The Minister’s decision was basedon theMinistry for Primary Industries’(MPI) risk analysis which was presented at the 2019 Scientific Committee meeting. The peer review of the risk analysis outlined in the 2019 SC report has not yet occurred.Here we review bycatch estimatesresulting from the MPI risk analysis and explore the likely level of bycatch following the 2020 management decision.As outlined below, MPI’s risk analysis combines several sources of information that result in under-estimatingthe level of bycatch,over-estimating the effectiveness of the management decisions taken in 2020 andthe species’ ability to continue to sustainimpacts.Some of theabundance estimates used in the risk analysis appear to bebiased high, are multipliedby a reproductive rate that is much higher than published estimates and an assumed figure for calf survival. This results in over-estimating thetotal number of dolphindeathseach year,from whichMPIsubtract their estimate of bycatch which isalmost certainly biased low. The remaining number of dolphins is apportioned a cause of death according to autopsy data from 55 Hector’s and Māuidolphins found dead on beaches. This is then compared to estimates of what level of takes would be sustainable, calculated using a formula (PST) that is not well understood and much less conservative than the international standard (PBR, developed by the US National Marine Fisheries Service).A further problem with the MPI approach is that its definition of “risk” does not relate to the risk of population decline or extinction, and is inconsistent with the modern understanding of the behaviour of meta-populations. Instead, itdefines risk as the likelihood of capture, which is apportioned to different areas according to fishing effort and predicteddolphin distributionbased on a habitat model. As a result,protection has beentargeted to areas where high densities of dolphins and high fishing effort coincide. Large populations wereallocated the highest level of protection, while small populations remain poorly protected.This approach is likely toincrease the risk of local extinctions, contractions of dolphin distribution, population fragmentation, loss of genetic variability and result in increased risk to the species as a whole.