Ringed Seals and Sea Ice in Canada’s Western Arctic: Harvest-Based Monitoring 1992–2011

Abstract

ABSTRACT. We examined the relationship between ringed seal body condition and reproduction and spring sea ice conditions in prime ringed seal habitat in Canada's western Arctic during 1992 -2011. Since 1970, ice conditions in east Amundsen Gulf and west Prince Albert Sound have shown only a slight trend toward earlier ice clearance (breakup) in spring (3 -7 days per decade) (p < 0.10) and no trend toward later freeze-up or increased variability in timing of spring ice clearance. A subsistence harvest -based sample of 2281 ringed seals was obtained during 1992 -2011 from Masoyak, a traditional hunting camp located on the northwest shore of west Prince Albert Sound and less than 5 km from east Amundsen Gulf. The results revealed a statistically significant trend of decreasing mean annual body condition of ringed seals (using an index of length-mass-blubber depth [LMD]: adults, 0.14 m /y) over the past two decades. A parallel result was that mean annual body condition of adults and subadults was correlated with the timing of fast ice clearance in spring (later ice clearance = worse condition). This correlation was most obvious in the extreme ice years in all sex/age groupings and was statistically significant for subadults. In mature females sampled since 1992, annual ovulation rates averaged 92.4 ± 16.3% (SD) and were greater than 80%, and mostly at 100%, in all years but two. Failure to ovulate was obvious in 2005, the most extreme late ice clearance year in our series, when only 30.0% of the mature adult females sampled ovulated. At the same time, values for seal body condition indices (adult females, LMD = 11.3; adult males, LMD = 12.4) and percent pups in the harvest (3.3%) were among the lowest recorded, and spring ice clearance was 38 d later than the 1992 -2011 average. While this and previous studies indicate that the seal population in this core habitat has recovered from natural and extreme-year sea ice fluctuations over the past four decades, the potentially magnified effect of several consecutive extreme ice years, compounded by the concurrent decline in seal body condition that we have now detected over the past 20 years, is of particular concern.Key words: ringed seal, Phoca hispida, ovulation, reproductive failure, body condition, Amundsen Gulf, Prince Albert Sound, sea ice, subsistence harvest, ice clearance RÉSUMÉ. Nous avons examiné le lien qui existe entre l'état corporel du phoque annelé, l'état de reproduction de ce phoque et l'état de la glace de mer printanière dans son habitat d'élection de l'ouest de l'Arctique canadien et ce, entre 1992 et 2011. Depuis 1970, l'état de la glace dans l'est du golfe Amundsen et dans l'ouest du détroit de Prince-Albert n'a affiché qu'une petite tendance vers une débâcle printanière plus hâtive (de 3 à 7 jours par décennie) (p < 0,10) et aucune tendance vers un englacement plus tardif ou une variabilité accrue caractérisant la période de la débâcle du printemps. Un échantillon recueilli à partir de 2 281 phoques annelés ayant fait l'objet d'une récolte de subs...

Seasonal Movements and Diving of Ringed Seals, <i>Pusa hispida</i>, in the Western Canadian Arctic, 1999–2001 and 2010–11

“…The seals were captured from shore at a site known locally as "Orhohivik" (70˚36′ N; 117˚18′ �), which is located in NW Prince Albert Sound, 17 km east of the seal monitoring site (Harwood et al, 2012b) and approximately 25 km southeast of Ulukhaktok, NT (Fig. 1).…”

“…Tags were attached to the back between the two front flippers� Both the glue and transmitter were warmed with a hair dryer before deployment to initiate hardening of the glue, which took about 20 min. Standard length, sex, weight, and claw age were determined for all seals that were livecaptured� Seals were classified as adults or subadults in the field by external examination and estimation of claw age� Seals were classified as adults if their claw age was greater than six (Smith, 1987;Harwood et al, 2012b).…”

“…Since they respond to ecosystem variation with changes in body condition (Moore, 2008;Moore et al, 2014), trends in seal body condition are a direct and useful link to the year-toyear availability and quality of the seals' prey. More than 2500 harvested ringed seals were sampled from this area during 1971 -79 (Smith, 1987(Harwood et al�, 2012b)� That monitoring study found a significant and sustained temporal trend of decreasing body condition of ringed seals since 1994, occurring in all age/sex classes and measured in spring just after breakup. The results of the present tagging study allow the general inference that seals sampled in the Harwood et al (2012b) study used winter habitats mainly in EAG and PAS.…”

“…Knowledge of habitats that the seals use for feeding in winter may contribute to our understanding of contemporary, sustained declines in seal body condition that have been observed in this area over the past two decades (Harwood et al, 2012b). We have as yet no detailed information about the distribution of Arctic cod in winter or the factors that control this distribution.…”

“…However, attempts to relate changes in the environment (Melling et al, 2005;Serreze et al, 2007;Walsh, 2008) to a marine mammal's responses to those changes, are often constrained by lack of baseline information about the species, its life history, prey, and critical habitats (Moore et al, 2014). Although the distribution, reproduction, and biology of the ringed seal (Pusa hispida) in the western Canadian Arctic have been the subject of scientific study for four decades (Stirling et al�, 1977(Stirling et al�, , 1982Smith, 1987;Kingsley and Byers, 1998;Harwood et al, 2000Harwood et al, , 2012bStirling, 2002), the seasonal movements and habitat use of ringed seals in Amundsen Gulf have not been explicitly examined to date.…”