Skip to main content

Long-term trends in reproductive and demographic parameters of female Northwest Atlantic hooded seals (Cystophora cristata): population responses to ecosystem change?

Buy Article:

$50.00 plus tax (Refund Policy)


More than 2500 ovaries were collected from Northwest Atlantic hooded seals (Cystophora cristata (Erxleben, 1777)) in the period 1956–2006 during moulting (data blocks: 1956–1960, 1970–1972, 1978), postmoulting (data blocks: 1990–1994, 1996–2006), and whelping (data blocks: 1967–1972, 1973–1976, 1979, 1983–1987, 1989–1995). Mean age at primiparity (MAP) was estimated as the mean age of females with a single corpus albicans or a corpus luteum from a postimplantation pregnancy. MAP was stable at 4.2–4.5 years during 1956–1978, increasing to 4.9–5.2 years in 1979 and to 6.1 years in 1989–1995 (later data insufficient). Patterns of corpus accumulation indicated occasional skipped pregnancies. This may have affected the accuracy of MAP estimates but not the main trends. Declining proportions of parae younger than 10 years after 1979 are consistent with effects of delayed maturation, reduced adult hunting mortality, and (or) increased juvenile mortality. From the 1990s, declining adult pregnancy rates are suggested by decreasing trends in proportions of older multiparae (8+) and other ovary-based proxies for pregnancy rates. Hooded seal abundance was largely stable from 1960 to the mid-1990s and changes in population parameters over this period are therefore more likely due to effects of ecosystem change on per-capita resource levels than population-mediated density dependence.

Keywords: Cystophora cristata; Northwest Atlantic; age at maturity; age at primiparity; mean maternal age; nord-ouest de l’Atlantique; âge maternel moyen; âge à la maturité; âge à la primiparité

Document Type: Research Article


Affiliations: 1: Institute of Marine Research, P.O. Box 6404, NO-9294 Tromsø, Norway. 2: Science Branch, Department of Fisheries and Oceans, Northwest Atlantic Fisheries Centre, St. John’s, NL A1C 5X1, Canada.

Publication date: 2012-03-01

More about this publication?
  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
  • Information for Authors
  • Submit a Paper
  • Subscribe to this Title
  • Terms & Conditions
  • Sample Issue
  • Reprints & Permissions
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free ContentFree content
  • Partial Free ContentPartial Free content
  • New ContentNew content
  • Open Access ContentOpen access content
  • Partial Open Access ContentPartial Open access content
  • Subscribed ContentSubscribed content
  • Partial Subscribed ContentPartial Subscribed content
  • Free Trial ContentFree trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more