Today’s oceans are undergoing rapid and unprecedented changes resulting from anthropogenic impacts. The North Atlantic right whale, one of the most endangered baleen whales with just over 500 animals remaining in the species, is one example of a species at risk resulting from human influence. Right whale vulnerability is chiefly attributed to injuries and mortalities caused by vessel collisions and fishing gear entanglement. Although understudied, prey-driven variability in calf production also contributes significantly to right whale population dynamics. Calanus finmarchicus, the lipid-rich copepod that right whales prey on, were anomalously abundant in the 1980s and 2000s, while concentrations were low in the 1990s. Synchronized with the low prey regime, right whale calf production in the 1990s was depressed relative to the surrounding decades. Using 32 years of right whale sighting and photo-identification data, we conducted a capture-recapture analysis to examine right whale demography during these three distinct decadal environmental regimes.
Results/Conclusions
Previous studies showed that modeled declines in survival and reproduction following the period of low population growth in the 1990s led to a predicted species extinction within 200 years. However, a climate-mediated increase in prey abundance in the new millennium has supported high reproduction rates in the critically endangered North Atlantic right whale, contributing to a resurgence in the population. These fluctuations in prey abundance were driven remotely by freshwater pulses from the Arctic Ocean, and by changes in advective supply to the Gulf of Maine related to North Atlantic circulation patterns. Forward projections show that even during conditions of low productivity similar to the 1990s, the right whale population trajectory will remain positive, and there is hope for species recovery. This study showcases the value of a broad investigation of an ecosystem and the underlying physical processes that influence lower trophic levels in place of a narrower, population-centric analysis. Future efforts in marine ecology and biodiversity management should trend towards “conservation oceanography” as unprecedented patterns in ocean temperature, chemistry and circulation influence ecosystem dynamics across ocean basins.