Availability, supply, and aggregation of prey (Calanus spp.) in foraging areas of the North Atlantic right whale (Eubalaena glacialis)

The North Atlantic right whale (NARW), Eubalaena glacialis, resides primarily on western North Atlantic continental shelves where this endangered species is susceptible to vessel strike and entanglement in fishing gear. Mitigation of these threats is dependent on the ability to predict variations in NARW occurrence. North of the Mid-Atlantic Bight, the distribution of NARWs is influenced by their prey, mainly copepods of the genus Calanus. We review factors that promote suitable foraging habitat from areas where NARWs have been observed feeding. We then synthesize our findings within a conceptual framework in which availability (i.e. shallow prey depth), supply, and aggregation of prey occur together to facilitate suitable foraging habitat. By definition, the depth of prey on the shelf is constrained to <= 200 m and other mechanisms may occur locally that further enhance prey availability. Enhanced production of prey occurs in coastal currents, which transport the copepods to NARW foraging areas. Prey concentrating mechanisms are not well-characterized. Information gaps that impede rapid and dynamic prediction of suitable foraging habitat include limited data on the spatial and temporal variation of prey and environmental conditions at local scales (i.e. 0.1-1 km), motility of prey, and diving behaviour of NARWs.