Research Document - 2011/130
Management implications of closure of estuaries to hunting of beluga in Nunavik
By T. Doniol-Valcroze, V. Lesage, and M.O. Hammill
Abstract
Beluga whales (Delphinapterus leucas) aggregate in large numbers in Nunavik estuaries during summer. Inuit hunters harvest beluga from a mix of stocks, designated after their specific summering areas. Processes by which fidelity to a summer area is maintained are uncertain, but since beluga calves spend 2-3 years with their mother, it is possible that adult-offspring transfer of information could be the basis for learning migratory pathways and site fidelity.
In the 1980’s, low estimates of beluga abundance for eastern Hudson Bay (EHB) and Ungava Bay (UB) stocks resulted in limits being placed on harvesting through a combination of total allowable takes (TAT) and regional closures. These closures included the permanent sanctuary in southern Ungava Bay at the Whale, Mucalic, Tuctuc and Tunulic rivers (1986), and seasonal closures at the Nastapoka (1990) and Little Whale (1995) rivers in eastern Hudson Bay. Here, we address the scientific rationale for keeping these estuaries closed, and the impact of this closure on beluga stocks and their management in Nunavik.
Satellite telemetry data from the Little Whale and Nastapoka rivers confirmed that beluga exhibit within-season site fidelity to a specific estuary. Most tagged individuals made repeated round-trips, often hundreds of kilometres away from the estuary, over the course of several weeks, but returned repeatedly to the same estuary. This pattern was observed for both males and females, but was variable among individuals, with round-trips outside estuaries lasting from one day to one month, and the number of round-trips ranging from 0 to 12.
An analysis of subsistence harvest data shows that beluga were likely to be captured in greater numbers in estuaries in a single hunting event than outside of estuaries. Recent genetic analyses indicated that beluga killed on the same day at the same summering sites were frequently closely related. Since more individuals are harvested in each hunting event inside estuaries, it is thus more likely that social groups with knowledge of specific migration routes could be eliminated. This could impede the recolonization of extirpated summering areas, and limit the exchange among stocks using different migration routes.
The strong philopatry of discrete stocks makes them vulnerable to overexploitation. At a finer scale in eastern Hudson Bay and Ungava Bay, dependence on a small number of specific estuaries makes beluga particularly vulnerable to the loss of critical habitat and has led to the disappearance of beluga from several estuaries. The closure of estuaries was aimed at limiting overharvesting and protecting a critical habitat where beluga could fulfill important biological needs. The two estuaries in eastern Hudson Bay that were closed to hunting are the only rivers where beluga have been sighted regularly from coastal aerial surveys over the last 25 years. Other estuaries now appear vacant, either following avoidance of disturbed sites or via depletion of a local herd. Recolonization of abandoned areas may have been hindered by the loss of knowledge of these locations among remaining animals.
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