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

Abstract

C. FINMARCHICUS ABUNDANCE Figure S1 shows the time series of the annual C. finmarchicus Abundance Index for the Gulf of Maine. It should be noted that NOAA funding cuts resulted in the Gulf of Maine Continuous Plankton Recorder (CPR) survey being discontinued in 2017. In addition, the survey route was changed in 2009, shifting its departure port from Boston, Massachusetts, to Portland, Maine. Therefore, coverage of Massachusetts Bay was discontinued, and coverage of the western Gulf of Maine was markedly different after 2009. Coverages of the eastern Gulf of Maine and western Scotian Shelf remained comparable. Results from a spatially and temporally resolved right whale reproduction model (Meyer-Gutbrod et al., 2015) demonstrated that when the summertime (third quarter–July, August, September) C. finmarchicus Abundance Index in the eastern Gulf of Maine falls below a certain threshold value, prenatal or neonatal calf mortality is triggered, presumably due to inadequate prey availability and poor maternal nutrition. This threshold value is shown in Figure S2, the time series of the summertime C. finmarchicus Abundance Index in the eastern Gulf of Maine. Due to the previously mentioned limitations in the availability of CPR survey data in the western Gulf of Maine during recent years, this threshold value could only be estimated, with the model using data through 2009. Because of this constraint, it was decided to show the threshold value in Figure S2 rather than in Figure 2c.