Beluga whale (Delphinapterus leucas) use of the Nelson River estuary, Hudson Bay

Abstract

Most beluga whales (Delphinapterus leucas) (Pallas 1776) living in areas of seasonal sea ice use estuaries periodically during summer. Beluga estuary-use hypotheses include feeding, calving, moulting, killer whale (Orcinus orca) predation, human predation, thermal advantage, and phylogenetic inertia. The hypotheses may not be mutually exclusive and may vary with populations or regions. This study describes aspects of beluga whale summer-ecology by studying the association between inter-annual water levels and beluga habitat selection in the Nelson River estuary. Flow rates from upstream Limestone Dam doubled from the dry years of 2002-2004 to the wet year of 2005. I used radio-tracking data (N=15, 2002-2005) and aerial surveys (2003, 2005) to test the hypothesis (H1) that belugas were farther out in the estuary during the wet year. Model variables included year, day, time, tide and age-sex. Observed location-habitat distances for the radio-tracking and aerial survey data were compared to the random equivalents using a Kolmogorov-Smimov (KS) test. A cumulative sign test determined the timing of a beluga shift in movement behaviour on August 10th. Pre-August 10th radio-tracking locations provided the spatial-temporal boundary of the Nelson River estuary. General Linear Models (GLM) for both the telemetry and aerial survey data show an association between beluga distance to the river-mouth and year. Study results provide evidence to weigh the main estuary-use hypotheses and contriubte to knowledge of beluga ecology and management.