NAMMCO Scientific Publications (Dec 2024)
Large decline in hooded seal (Cystophora cristata) pup production off of northeastern Newfoundland in 2012 and 2017
Abstract
Accurate data on population abundance is needed to monitor trends through time, especially for species that are commercially harvested or vulnerable to climate change related impacts. Hooded seals (Cystophora cristata) in the Northwest Atlantic whelp on drifting sea ice in three areas: Davis Strait, the southern Gulf of St. Lawrence and off of northeastern Newfoundland (“Front”), Canada, with the majority of whelping (>90%) occurring at the Front. They are harvested in Canada and Greenland but have not been assessed since 2005. Aerial surveys for harp seals (Pagophilus groenlandicus) took place at the Front in 2012 and 2017. These surveys also captured the vast majority of hooded seal whelping patches in these years and so were used to estimate hooded seal pup production at the Front. Pup production was estimated from photo (2012 and 2017) and visual (2017 only) line-transect surveys. Staging data from 2004, 2005 and 2017 were used to correct these estimates for the proportion of pups not born on the survey days, resulting in total pup production estimates of 41,129 (SE = 7,374) and 39,021 (SE = 18,334) pups in 2012 and 2017, respectively. This is a large decrease from the previous estimate, being 38% and 36%, respectively, of the pup production estimated on the Front in 2005. Extensive reconnaissance that failed to locate whelping hooded seals in Davis Strait (2024) or outside the traditional whelping area at the Front (2012, 2017), along with low sea-ice coverage in the Gulf of St. Lawrence makes it unlikely that significant whelping was redistributed to other areas. The large decline in pup production after 2005 mirrors a similar decline and continued low level of pup production for hooded seals in the Greenland Sea that occurred between 1997 and 2005/07. Although the cause of the decline in the Northwest Atlantic is unknown, it is possible that negative impacts of ecosystem change on female fecundity and juvenile survival, as has been documented for harp seals in the Northwest Atlantic, are also impacting hooded seals.
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