North Atlantic right whale habitat in the southern Gulf of St Lawrence


The distribution of North Atlantic right whales has shifted in the last decade, perhaps best exemplified by the decreased use of several well-characterized habitats in the Gulf of Maine and Scotian Shelf and an increased occupancy of a relatively unknown habitat in the southern Gulf of St. Lawrence (GSL). The goal of this project was to characterize right whale feeding habitat in the GSL region. We conducted opportunistic oceanographic sampling during daylight hours from visual survey vessels in the presence and absence of right whales in July and August over three years (2017 – 2019). Oceanographic stations (n = 115) were typically comprised of a depth-integrated oblique ring net tow that was preceded and followed by a vertical profile with a conductivity-temperature-depth (CTD) instrument and optical plankton counter (OPC; 2018/2019 only). Small copepods (e.g., Centropages, Psuedocalanus) were numerically dominant at all stations. Of the Calanus species, C. finmarchicus was typically most abundant but C. hyperboreus appeared to comprise the majority of total Calanus biomass based on their abundance and relative body size (biomass estimation is pending). Physical and biological variables were derived at each station and logistic regressions were used to quantify right whale habitat associations. Results suggested a higher probability of right whale presence was associated with a shallow bottom mixed layer characterized by relatively warm saline water, and abundant patches of late-stage Calanus near the seafloor. Further research is underway to better characterize the deep Calanus layer and explore the potential role of alternative foraging strategies (e.g., feeding on other taxa). These results offer insights into the quantity of the prey and quality of the GSL as a right whale foraging habitat and the associated implications for right whale recovery.

North Atlantic Right Whale Consortium