Variation in body size of ringed seals (Pusa hispida hispida) across the circumpolar Arctic: evidence of morphs, ecotypes or simply extreme plasticity?

  • Kit M. Kovacs Norwegian Polar Institute, Fram Centre, Tromsø, Norway
  • John Citta Alaska Department of Fish and Game, Fairbanks, AK, USA
  • Tanya Brown Department of Fisheries and Oceans, Vancouver, BC, Canada
  • Rune Dietz Department of Bioscience, Marine Mammal Research, Aarhus University, Roskilde, Denmark
  • Steve Ferguson Fisheries and Oceans Canada, Winnipeg, MB, Canada
  • Lois Harwood Fisheries and Oceans Canada, Yellowknife, NT, Canada
  • Magali Houde Environment and Climate Change Canada, Montreal, QB, Canada
  • Ellen V. Lea Fisheries and Oceans Canada, Inuvik, NT, Canada
  • Lori Quakenbush Alaska Department of Fish and Game, Fairbanks, AK, USA
  • Frank Riget Greenland Institute for Natural Resources, Nuuk, Greenland
  • Aqqalu Rosing-Asvid Greenland Institute for Natural Resources, Nuuk, Greenland
  • Tom G. Smith EMC Eco Marine Corp, Garthby, QB, Canada
  • Vladimir Svetochev Murmansk Marine Biological Institute, Russian Academy of Sciences, Murmansk, Russia
  • Olga Svetocheva
  • Christian Lydersen Norwegian Polar Institute, Fram Centre, Tromsø, Norway
Keywords: Density-dependence, ecology, food availability, morphometry, pinniped, phocid seal

Abstract

The ringed seal is a small phocid seal that has a northern circumpolar distribution. It has long been recognized that body size is variable in ringed seals, and it has been suggested that ecotypes that differ in size exist. This study explores patterns of body size (length and girth) and age-at-maturity across most of the Arctic subspecies’ range using morphometric data from 35 sites. Asymptotic lengths varied from 113 to 151 cm, with sites falling into five distinct size clusters (for each sex). Age-at-maturity ranged from 3.1 to 7.4 years, with sites that had early ages of sexual maturity generally having small length-at-maturity and small final body length. The sexes differed in length at some sites, but not in a consistent pattern of dimorphism. The largest ringed seals occurred in western Greenland and eastern Canada, and the smallest occurred in Alaska and the White Sea. Latitudinal trends occurred only within sites in the eastern Canadian Arctic. Girth (with length and season accounted for) was also highly variable but showed no notable spatial pattern; males tended to be more rotund than females. Genetic studies are needed, starting with the “giants” at Kangia (Greenland) and in northern Canada to determine whether they are genetically distinct ecotypes. Additional research is also needed to understand the ecological linkages that drive the significant regional size differences in ringed seals that were confirmed in this study, and also to understand their implications with respect to potential adaptation to climate change.

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Published
2021-09-30
How to Cite
Kovacs, K. M., Citta, J., Brown, T., Dietz, R., Ferguson, S., Harwood, L., Houde, M., Lea, E. V., Quakenbush, L., Riget, F., Rosing-Asvid, A., Smith, T., Svetochev, V., Svetocheva, O., & Lydersen, C. (2021). Variation in body size of ringed seals (<em>Pusa hispida hispida</em&gt;) across the circumpolar Arctic: evidence of morphs, ecotypes or simply extreme plasticity?. Polar Research, 40. https://doi.org/10.33265/polar.v40.5753
Section
Research Articles