Research Document - 2014/025

Changes in ice conditions and potential impact on harp seal pupping

By M.O. Hammill and G.B. Stenson

Abstract

Harp seals require stable ice as a platform for resting, pupping and rearing their young. Changes in ice cover in Atlantic Canada during the period of pupping and when the young animals or beaters are leaving the ice to forage on their own were examined between 1969 and 2013, using ice cover data from Environment Canada. The annual extent of ice cover has varied considerably, particularly in the Gulf of St Lawrence (Gulf). Overall, ice cover has declined during the pupping period, due to a decline in ice cover in the Gulf of St Lawrence. No significant trend in ice cover in southern Labrador, which includes the area known as the Front, was observed over the last 44 years. However, a decline in ice cover during April was observed at both the Front and in the Gulf. There is no direct measure of mortality in the harp seal assessment. Mortality of young of the year associated with very poor ice conditions has been identified and incorporated into the assessment since 2003. This mortality index is qualitative being based on expert opinion. An index was developed, based on the magnitude of the negative ice anomaly for the Gulf and the Front. This index suggests that ice related mortality may have been as high as 65% of the total number of pups born in 1969 and 2011.

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