Research Document - 2010/136

Current Reproductive and Maturity Rates of Northwest Atlantic Harp Seals, (Pagophilus groenlandicus)

By G.B. Stenson and N.J. Wells

Abstract

Obtaining accurate estimates of fecundity are critical for estimating the population dynamics of a species. Annual estimates of late term pregnancy rates, fecundity and mean age of sexual maturity of Northwest Atlantic harp seals were obtained from samples collected off the coast of Newfoundland and Labrador between 1954 and 2008. Pregnancy rates among 3 year olds remained low (<10 %) throughout the time period while those of 4 and 5 year olds initially increased during the 1970s, but declined by the mid 1980s to levels similar to, or lower than, those seen in the 1960s. Pregnancy rates of older seals remained high until the mid 1980s, but then declined to their current low levels. Annual fecundity rates are highly variable. Although they remained high (>85%) until the late 1970s, they subsequently declined and remain low. The increasing trend in mean age of sexual maturity observed since the 1990s has continued.  Reproductive rates increased slightly in 2007 and 2008, but are not as high as observed in the 1970s. 

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