Mapping and Understanding the Role of Seabed Morphology in Relation to Beluga Whale (Delphinapterus leucas) Hotspots and Habitat Use in the Mackenzie Estuary, NT

The Tarium Niryutait Marine Protected Area within the Mackenzie Estuary provides a critical summer habitat for the Eastern Beaufort Sea (EBS) beluga whales (Delphinapterus leucas). Given the lack of seabed characterization in the Mackenzie Estuary, there is a need to characterize key features and governing processes that may influence or drive beluga habitat use. Thus, we sample and describe the Mackenzie Estuary seabed and examine the influence of ice conditions, fluvial processes and wave interactions to define seabed processes and spatially defined habitats. Lastly, we examine how beluga selects specific seabed characteristics or habitat types. Seabed mapping, sediment sampling and delineation of seafloor features are used to define the seabed habitat. The majority of the seabed consists of medium to coarse-grained silt and is void of any bathymetric variations and disturbances. Five seabed habitat zones were defined: (1) featureless and flat, (2) scours and disturbed, (3) sandy shoal, (4) deep channel and (5) longshore bars. Beluga observations analysed retrospectively from 1972 to 1992 were associated with the featureless and flat seabed habitat 72% of the time. However, a preference for the sandy shoal habitat provides some indication there are substrates in the estuary which are suitable for whales to rub against (to scrape off moulting skin), supporting the hypothesis there are certain habitats that may attract belugas during the annual moult.