Stock discrimination of Atlantic walrus (Odobenus rosmarus rosmarus) in the eastern Canadian Arctic using lead isotope and element signatures in teeth

Abstract

Atlantic walrus (Odobenus rosmarus rosmarus) harvested from three regions of the Canadian Arctic, and by different communities within two of those regions, were distinguished using the stable Pb isotope or trace element composition of their tooth cementum. Walrus from Foxe Basin (Igloolik, Hall Beach), the High Arctic (Grise Fiord, Resolute Bay), and eastern Hudson Bay (Akulivik, Inukjuak) were each characterized by specific combinations of Pb isotope ratios and Co concentrations, and we conclude that they represent different regional stocks. Walrus landed at Akulivik and Inukjuak were further discriminated by significant differences in 208Pb/207Pb, even though the communities are only 250 km apart. There was more overlap between walrus from Igloolik and Hall Beach, which are 80 km apart, but significant differences between sites in Pb isotope ratios and in concentrations of V, Zn, and Mo suggested that more than one Foxe Basin stock was being harvested. Particularly at Hall Beach, the herds contained a few individuals with isotope ratios significantly different from the rest of the population. These "outliers" may represent either immigrants from other geological provinces or animals caught in other areas. Further investigation of the outliers could provide information regarding hunting patterns, walrus home ranges, and the rates and demographics of interstock migrations.