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

• Published in: ARCTIC
• Main Authors: Harwood, Lois A., Smith, Thomas G., Melling, Humfrey, Alikamik, John, Kingsley, Michael C.S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Arctic Institute of North America 2012
• Subjects: ringed seal; Phoca hispida; ovulation; reproductive failure; body condition; Amundsen Gulf; Prince Albert Sound; sea ice; subsistence harvest; ice clearance; phoque annelé; échec de reproduction; état corporel; golfe Amundsen; détroit de Prince-Albert; glace de mer; récolte de subsistance; debacle; Arctic; Sea ice
• Online Access: https://journalhosting.ucalgary.ca/index.php/arctic/article/view/67283

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 m1.5/kg0.5/y; subadults, 0.24 m1.5/kg0.5/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 ...