Reproductive Rates of Harp Seals, Pagophilus groenlandicus (Erxleben)

• Published in: Journal of the Fisheries Research Board of Canada
• Main Author: Sergeant, D. E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1966
• Subjects: General Medicine; White Sea; Jan Mayen; Newfoundland; Pagophilus groenlandicus
• Online Access: http://dx.doi.org/10.1139/f66-066; http://www.nrcresearchpress.com/doi/pdf/10.1139/f66-066

In less than a decade the mean age at sexual maturity of female harp seals of the Front, or northeastern Newfoundland population, decreased to 4 from [Formula: see text] years. Exploitation was heavy during this period and included a high proportion of seals older than 1 year. Females of the Gulf of St. Lawrence herd declined in mean age at sexual maturity over the same decade to 5 from nearly 6 years. Exploitation of this herd was lower, especially for animals older than their first year. Fertility of the adult females was likely higher in the more heavily exploited population. Published data on the White Sea population, which was reduced to low numbers, show reproduction at a lower mean age than for the present Front herd; for the Jan Mayen herd, of uncertain population status, about the same reproductive rate as the present Gulf herd. In most of the populations, samples of adult, whelped females showed the greatest number in the age-class about 1 year older than that first showing 100% of the females mature, as would be expected; however, samples from the Front herd showed dominance of an older age-class, suggesting that young adult females may to some extent segregate into separate groups. The immediate factors leading to increased reproductive rates at lower population densities were not elucidated.