MEPS 264:137-154 (2003)  -  doi:10.3354/meps264137

ABSTRACT: Simultaneous visual and oceanographic surveys were conducted in the lower Bay of Fundy and in Roseway Basin of the SW Scotian Shelf during the summers of 1999 to 2001 to investigate the physical and biological oceanographic factors associated with North Atlantic right whale occurrence. Sightings of right whales were recorded along predetermined transects through each region, while both in situ and remotely sensed oceanographic measurements were collected. Sampling with plankton nets and an optical plankton counter confirmed that right whales in these regions feed on Calanus finmarchicus copepodite stage 5 (C5). Spatial variability in right whale occurrence was associated with water depth and the depth of the bottom mixed layer. C. finmarchicus C5 aggregated over the deepest water depths in both regions, and within these areas, right whales occurred where the bottom mixed layer forced discrete layers of C. finmarchicus C5 to occur shallower in the water column (allowing more efficient foraging). Annual increases in right whale occurrence appeared to be associated with decreases in sea surface temperature (SST) in both regions; however, this observation merits caution in light of the short duration of the study (3 yr). There was also evidence to suggest that both spatial and interannual variability in right whale occurrence in Roseway Basin may be associated with SST gradient, a proxy for ocean fronts.

KEY WORDS: Eubalaena glacialis · Distribution · Habitat · Calanus finmarchicus · Fronts · Gulf of Maine · Roseway Basin · AVHRR · SeaWiFS · Optical plankton counter