Climate-associated changes in prey availability drive reproductive dynamics of the North Atlantic right whale population

Considered one of the most endangered cetacean species, the North Atlantic right whale Eubalaena glacialis suffered declining abundance during the 1990s due to a high rate of anthropogenic-associated mortality and a low rate of reproduction. Previous studies have suggested that the reproductive rate is tightly coupled to the abundance of Calanus finmarchicus in the Gulf of Maine (GOM), which has been shown to respond to ecosystem regime shifts associated with decadal-scale climate forcing from the Arctic. Given the endangered status of the right whale population, it is vital to determine how climate-associated changes in prey availability will affect this species in the future. Here, we investigate a 3-state reproduction model that explores multiple environmental proxies as potential predictors of annual calf production during the period from 1980 to 2007. The model achieves its best fit to observations using temporally and spatially resolved C. finmarchicus abundance data derived from Continuous Plankton Recorder (CPR) surveys of the GOM. Building on previous research, this prey-dependent model, which uses bimonthly and geographically specific abundance anomalies of C. finmarchicus, significantly improves estimates of annual calf production relative to a null model. The temporal and geographic distributions of prey objectively chosen for inclusion in the new version of the model correspond well with observed right whale seasonal distribution patterns, providing further evidence that the model captures essential features of right whale reproductive ecology.