Climate-induced changes to North Atlantic right whale habitat use and demography

Sea surface temperatures in the shelf waters in the Gulf of Maine (GOM) are warming faster than 99% of the global ocean. Warming during the past decade has coincided with the endangered North Atlantic right whale (Eubalaena glacialis) population’s seasonal abandonment of traditional feeding grounds in this region. The right whale’s unexpected shift into new habitats in the Gulf of St. Lawrence (GSL) led to a mortality of at least 5% of the population since 2017 due to inadequate management for the prevention of ship strikes and fishing gear entanglement. The right whale population is also suffering from declining birth rates linked to changes in the distribution and abundance of their primary prey species, Calanus finmarchicus. Here we investigate the hypothesis that changes in ocean circulation, characterized by indices such as the Regional Slope Water Temperature and the Gulf Stream Index, are altering advective pathways for C. finmarchicus and other zooplankton into the deep basins of the GOM. We use time series analysis to examine the links between physical oceanographic and climate indices, C. finmarchicus abundance, and right whale population dynamics. Over 60 years of life-stage specific C. finmarchicus samples were analyzed at high spatial and temporal resolution collected by the GOM Continuous Plankton Recorder. Right whale habitat use and demography was characterized by over 70,000 sightings compiled by the North Atlantic Right Whale Consortium. Identification of the oceanographic regimes that triggered recent transitions in right whale behavior may be useful in predicting future patterns of habitat use. Accurate forecasts of right whale distribution and viability are critical for designing effective fishery closures, gear alterations and shipping regulations to reduce anthropogenic mortalities.