Research Document - 2016/050
Modelling walrus population dynamics: A direction for future assessments
By M.O. Hammill, T. Doniol-Valcroze, A. Mosnier, J.-F. Gosselin
Abstract
Walruses are harvested for subsistence in northern Canada. In this study a surplus production model was fitted to aerial survey data of abundance using Bayesian methods. The model was fitted to abundance data from two stocks: the Hudson Bay-Davis Strait stock and the Foxe Basin stock. The model estimated that walrus abundance in the northern Hudson Bay region of the Hudson Bay-Davis Strait stock declined from approximately 10,400 animals (rounded to the nearest 100) in 1954 to a minimum of 3,900 animals in 1986, but has increased since then to 7,000 walruses (95% Credibility Intervals =4,100–10,800). The model estimated a current population abundance in Foxe Basin of 12,500 (95% Credibility Intervals 8,600–18,500, rounded to the nearest 100). This population appears to have remained stable over the last 60 years. Walrus are considered Data Poor, consequently, Total Allowable Removals have been estimated using the Potential Biological Removal method. The population model can be used to provide inputs needed to estimate allowable removals. Given more data, the population model can be used to evaluate the probability that different harvest scenarios will meet management objectives.
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