Beluga whale Delphinapterus leucas late summer habitat use and support for foraging areas in the Canadian Beaufort Sea

The eastern Beaufort Sea beluga whale Delphinapterus leucas population aggregates in the Mackenzie Estuary every summer, and moves toward the continental shelf and offshore waters in the late summer. From 2007 to 2009, systematic aerial surveys recorded beluga whale locations beyond the estuary, over the Mackenzie Shelf and offshore waters, where distributions were observed to occur widely. It is thought that beluga use of the offshore is primarily driven by feeding opportunities, and historical abundance trends suggest that the offshore may have become more attractive to beluga in response to prey availability. To determine drivers of beluga late summer habitat use, a resource selection function (RSF) model was used to measure se lection of 4 key environmental variables: (1) chlorophyll a, (2) sea surface temperature, (3) bathymetry and (4) distance from shore. Results revealed that all 4 variables contributed significantly to the individual 2007, 2008 and 2009 best-fit habitat models. Beluga preferred warmer sea surface temperatures (> 2 degrees C) and mid-to-high chlorophyll a concentrations (0.01-10 mg m(-3)), conditions that are indicative of enhanced local productivity and/or upwelling. Beluga distributions varied slightly between years, although high-use areas were identified in nearshore waters (0-50 m) offshore of the Tuktoyaktuk Peninsula, and along the continental shelf-slope (100-500 m), a region known to support a principal prey species, Arctic cod Boreogadus saida. This study improved knowledge of beluga habitat use in the offshore and revealed that selection of late summer oceanographic variables may provide support for foraging habitats, as these dynamic conditions are important to structuring forage fish ecosystems.