[MARMAM] new papers on ringed seal ecology

Magaly Chambellant mchambellant at hotmail.com
Mon Apr 2 03:22:36 PDT 2012








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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