I'm pleased to announce the publication of the following papers on ringed seal
ecology:
Temporal variations in Hudson Bay ringed seal (Phoca hispida) life-history
parameters in relation to environmentMagaly Chambellant, Ian Stirling, William
A. Gough, and Steven H. Ferguson
We related temporal variation in the environment to demographic parameters and
body condition of ringed seals (Phoca hispida)
in Hudson Bay, near the southern limit of the species' geographic
range. Ringed seals harvested by Inuit hunters for subsistence purposes
in Arviat, Nunavut, Canada, from 1991 to 2006 were measured and sampled.
Ringed seal ovulation rate did not change over time, but pregnancy rate
and percent pups in the fall harvest increased in the 2000s, compared
to the 1990s. Ringed seals grew faster and attained sexual maturity
earlier in life, and the population age structure shifted to younger age
classes in the 2000s compared to the 1990s. Ringed seal demographic
parameters were characteristic of a population in decline in the 1990s
and a growing population in the 2000s. A quadratic polynomial regression
best described the relationship between percent pups in the harvest and
snow depth, and between pup and adult female body condition index and
date of spring breakup, suggesting that ringed seals have evolved to do
best within a relatively limited range of environmental conditions. We
propose that the decline of ringed seal reproductive parameters and pup
survival in the 1990s could have been triggered by unusually cold
winters and heavy ice conditions that prevailed in Hudson Bay in the
early 1990s, through nutritional stress and increased predation
pressure. The recovery in the 2000s may have been augmented by
immigration of pups, juveniles, and young adult ringed seals into the
study area. We discuss the possibility of a decadal-scale biological
cycle that reflects fluctuations in climatic variables, and particularly
in the sea ice regime.
Journal of Mammalogy 93(1):267-281. 2012
doi: http://dx.doi.org/10.1644/10-MAMM-A-253.1
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Temporal variation in distribution and density of ice-obligated seals in
western Hudson Bay, Canada
Magaly Chambellant, Nicholas J. Lunn and Steven H. Ferguson
Recent unidirectional climatic trends and changes in top predator
population ecology suggest that long-term modifications
may be happening in Hudson Bay, Canada. Effects of such
changes on ice-obligated seal populations are expected but long-term
studies are required to differentiate climate-induced
changes from natural variation. We conducted strip-transect surveys
in late spring in 1995–1997, 1999–2000 and 2007–2008 to
estimate distribution, density and abundance of ice-obligated ringed
(Phoca hispida) and bearded (Erignathus barbatus)
seals in western Hudson Bay. When hauled out, ringed seals preferred
land-fast and consolidated pack ice, whereas bearded
seals preferred unconsolidated pack ice. Bearded and ringed
seal density estimates varied from 0.0036 to 0.0229 seals/km2 of ice and from
0.46 to 1.60 seals/km2
of ice, respectively. Strong inter-annual variations were recorded in
the abundance estimates of both species, with the largest
abundance estimates in 1995 (104,162 and 1,494 ringed and
bearded seals, respectively) and the lowest in 2008 for ringed seals
(33,701) and 1997 for bearded seals (278). A sine function
best described seal density estimates in western Hudson Bay and
suggested a decadal cycle. Previous studies that reported
low ringed seal demographic parameters in the 1990s and a recovery
in the 2000s supported our interpretation of the survey
results. We discuss our results in the context of climate warming
and suggest that a long-term decline in ice-obligated seal
density estimates may overlay a possible natural decadal cycle.
Polar Biology
DOI: 10.1007/s00300-012-1159-6 (online first)
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