Beluga whale (Delphinapterus leucas) summer habitat associations in the Nelson River estuary, Western Hudson Bay
Locations of satellite-tagged and aerial surveyed beluga whales (Delphinapterus leucas (Pallas, 1776)) in the Nelson River Estuary, southwest Hudson Bay were recorded from midsummer to late fall in 2002–2005. Data for the drier than average years of 2002–2004 (average of 19% decreased flow) were compared to the wetter than average year of 2005 (57% increased flow) to examine their seasonal movements and habitat associations including the influence of the freshwater plume from an upstream hydroelectric dam. A change point technique (CUMSUM test) estimated the change date in beluga movements from localized to migratory, delineating the estuary from the belugas perspective.
Both tracking and aerial survey data indicated that belugas were farther from the river mouth and channel during 2005, but not farther from the nearest shore. In this estuary, proximity to freshwater may be more important than the selection of shallow water. We determined a behavioural shift in beluga movement patterns on 9 August indicating that prior locations comprised the main period of estuary use, with migratory behaviour after this date. Surveys of Western Hudson Bay belugas from the late 1940s to late 1960s coincide with our findings and suggest that there has been no major change in migration timing despite the evidence for a warming Hudson Bay. Our results on inter-annual changes in the movements of belugas add to a growing body of knowledge outlining the life history relevance of beluga estuary use. We discuss the management implications of our results relative to hydroelectric activity and beluga estuary use hypotheses.