Ten thousand and increasing: Is the western Arctic population of bowhead whale endangered?

Based on a series of 11 abundance estimates over 23 years, the western Arctic population of bowhead whale (WABW) has recovered substantially since it was listed under the US Endangered Species Act. We evaluate extinction risk for WABW to determine if this population should be considered for reclassification under the ESA. Given the uncertainty associated with distinguishing process error and observation error, we consider three scenarios reflecting different assumptions for process error. We applied the quantitative criteria for recovery and delisting using the approach proposed by [Gerber, L.R., DeMaster, D.P., 1999. An approach to endangered species act classification of North Pacific humpback whales. Conservation Biology, 13, 1203–1214] for large whales. To further examine the monitoring process and make recommendations for future data needs, we then re-ran the model using progressively smaller sub-samples of the census data. As longer time series of data were considered, the fraction of outcomes consistent with a “delisting” decision increased. For the 10 and 11-census year subsets, data unequivocally support a decision to delist this population for the 3 scenarios. Furthermore, the IUCN criteria for endangered and vulnerable are not met for this population of bowhead whale under any of our scenarios. Results from the population projections and application of the risk classification criteria are consistent with a determination that the risk of extinction for this population is insignificant in the foreseeable future.