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1 February 2011 Detecting Density Dependence in Recovering Seal Populations
Carl Johan Svensson, Anders Eriksson, Tero Harkonen, Karin C. Harding
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Time series of abundance estimates are commonly used for analyses of population trends and possible shifts in growth rate. We investigate if trends in age composition can be used as an alternative to abundance estimates for detection of decelerated population growth. Both methods were tested under two forms of density dependence and different levels of environmental variation in simulated time series of growth in Baltic gray seals. Under logistic growth, decelerating growth could be statistically confirmed after 16 years based on population counts and 14 years based on age composition. When density dependence sets in first at larger population sizes, the age composition method performed dramatically better than population counts, and a decline could be detected after 4 years (versus 10 years). Consequently, age composition analysis provides a complementary method to detect density dependence, particularly in populations where density dependence sets in late.

© Royal Swedish Academy of Sciences 2011
Carl Johan Svensson, Anders Eriksson, Tero Harkonen, and Karin C. Harding "Detecting Density Dependence in Recovering Seal Populations," AMBIO: A Journal of the Human Environment 40(1), 52-59, (1 February 2011).
Received: 29 March 2010; Accepted: 24 August 2010; Published: 1 February 2011

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Age-structured populations
Density-dependent population growth
Detecting population trends
environmental stochasticity
population management
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