Ocean Regime Shift is Driving Collapse of the North Atlantic Right Whale Population

Erin Meyer-Gutbrod,Charles Greene,Kimberley Davies,David Johns

doi:10.5670/oceanog.2021.308

Abstract

Ocean warming linked to anthropogenic climate change is impacting the ecology of marine species around the world. In 2010, the Gulf of Maine and Scotian Shelf regions of the Northwest Atlantic underwent an unprecedented regime shift. Forced by climate-driven changes in the Gulf Stream, warm slope waters entered the region and created a less favorable foraging environment for the endangered North Atlantic right whale population. By mid-decade, right whales had shifted their late spring/summer foraging grounds from the Gulf of Maine and the western Scotian Shelf to the Gulf of St. Lawrence. The population also began exhibiting unusually high mortality in 2017. Here, we report that climate-driven changes in ocean circulation have altered the foraging environment and habitat use of right whales, reducing the population’s calving rate and exposing it to greater mortality risks from ship strikes and fishing gear entanglement. The case of the North Atlantic right whale provides a cautionary tale for the management of protected species in a changing ocean.

Highlights

Ocean warming linked to anthropogenic climate change is impacting the migration and distributional patterns of many marine species around the world (Greene, 2016; Scannell et al, 2016; Frölicher et al, 2018; Smale et al, 2019)
The Gulf of Maine/western Scotian Shelf region is situated in an oceanographic transition zone, one that is strongly influenced by fluctuations in the Labrador Current system to the north and the Gulf Stream to the south
The analyses of long-term data sets reported here provide evidence supporting the hypothesis that a climate-driven regime shift in the Gulf of Maine/western Scotian Shelf region occurred in 2010 and impacted the foraging environment, habitat use, and demography of the right whale population

Summary

Introduction

Ocean warming linked to anthropogenic climate change is impacting the migration and distributional patterns of many marine species around the world (Greene, 2016; Scannell et al, 2016; Frölicher et al, 2018; Smale et al, 2019). Atlantic’s Gulf of Maine and western Scotian Shelf have been warming more rapidly than most of the global ocean (Figure 1; Pershing et al, 2015; Greene, 2016; Scannell et al, 2016; Seidov et al, 2021). As this region has warmed, the North Atlantic right whale, Eubalaena glacialis, began abandoning some of its traditional foraging grounds (Pettis et al, 2020). With an elevated mortality rate and depressed calving rate, the right whale population has declined by an estimated 26% this decade and now is thought to number fewer than 360 individuals

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