Research Document - 2014/022

Abundance Estimates of Northwest Atlantic Harp seals and Management advice for 2014

By M.O. Hammill, G.B. Stenson, A. Mosnier and T. Doniol-Valcroze

Abstract

A population model was used to examine changes in the size of the Northwest Atlantic harp seal population between 1952 and 2014. The model incorporated information on reproductive rates, reported removals, estimates of non-reported removals and losses through bycatch in other fisheries to determine the population trajectory. The model was fit to 12 estimates of pup production from 1952 to 2012, and to annual estimates of age-specific pregnancy rates between 1954 and 2013. Pup production declined throughout the 1960s reaching a minimum in 1971, and then increased to a maximum in 2008. Pup production and total population size in 2012 are estimated to be 929,000 (SE=148,000) and 7,445,000 (SE=698,000), respectively. The maximum estimated population size, Nmax, was estimated to be 7.8 million animals in 2008. Projecting forward to 2014, the estimated pup production is 853,000 (SE=202,000) and total population size is 7,411,000 (SE=656,000). The population appears to be relatively stable, showing little change in abundance since the 2004 survey, although pup production has become highly variable among years. Data on age-specific pregnancy rates indicate that herd productivity has declined compared to the 1980s and early 1990s. However, relatively few reproductive samples have been obtained in recent years which contributes to our uncertainty surrounding the population estimate.

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