Using Ocean Gliders to Evaluate the Partitioning of a Shallow Coastal Basin Habitat by Baleen Whales in the Northwest Atlantic

Abstract

The availability and abundance of low trophic-level baleen whale prey is coupled, to varying degrees, to oceanographic processes. Therefore, the distribution of baleen whales in a feeding habitat should also be linked to variation in those processes. Assessment of these linkages is challenging because of the difficulty in obtaining sufficient spatially and temporally concurrent in situ observations of the whales and local oceanographic properties. We collected a multi-year series of concurrent acoustic whale detections and high-resolution oceanographic measurements to evaluate how baleen whales may partition their feeding habitat. The focal habitat was Roseway Basin, a relatively small (30x60 km), shallow (<180 m) basin on the Scotian Shelf located ~40 km seaward of SW Nova Scotia. Data were collected during annual fall glider surveys of the Basin over a 3-yr period (2014-16). Gliders were equipped to record high resolution full-depth profiles of salinity, temperature, and depth as well as audio to record and classify whale sounds. A suite of oceanographic variables were derived from each profile (n = 5808) and paired with concurrent detections of right (n = 57), fin (n = 997), sei (n = 125), and humpback (n = 30) whales. Linear discriminate function analysis was used to evaluate how each species partitioned oceanographic properties of the habitat. Preliminary analyses indicate that fin whale detections were ubiquitous; more likely related to their long-range acoustic detectability than to favourable oceanographic conditions. In contrast, right, sei, and humpback whales were clearly associated with different oceanographic conditions; right whales, for example, occurred more often in well-stratified water columns overlying high-density bottom waters, consistent with conditions previously demonstrated to have a role in aggregating their copepod prey at depth in shelf basins.

Date
Event
Society of Marine Mammalogy Conference
Location
Halifax, Nova Scotia
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