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Shifting trends: detecting environmentally mediated regulation in long-lived marine vertebrates using time-series data

McMahon, Clive Reginald, Bester, M., Hindell, Mark A., Brook, Barry William and Bradshaw, Corey J. A. (2009). Shifting trends: detecting environmentally mediated regulation in long-lived marine vertebrates using time-series data. Oecologia,159(1):69-82.

Document type: Journal Article
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IRMA ID 79264438xPUB27
Title Shifting trends: detecting environmentally mediated regulation in long-lived marine vertebrates using time-series data
Author McMahon, Clive Reginald
Bester, M.
Hindell, Mark A.
Brook, Barry William
Bradshaw, Corey J. A.
Journal Name Oecologia
Publication Date 2009
Volume Number 159
Issue Number 1
ISSN 1432-1939   (check CDU catalogue  open catalogue search in new window)
Start Page 69
End Page 82
Total Pages 14
Place of Publication Heidelberg, Germany
Publisher Springer Berlin
HERDC Category C1 - Journal Article (DEST)
Abstract Assessing the status and trends in animal populations is essential for effective species conservation and management practices. However, unless time-series abundance data demonstrate rapid and reliable fluctuations, objective appraisal of directionality of trends is problematic. We adopted a multiple-working hypotheses approach based on information-theoretic and Bayesian multi-model inference to examine the population trends and form of intrinsic regulation demonstrated by a long-lived species, the southern elephant seal. We also determined the evidence for density dependence in 11 other well-studied marine mammal species. (1) We tested the type of population regulation for elephant seals from Marion Island (1986–2004) and from 11 other marine mammal species, and (2) we described the trends and behavior of the 19-year population time series at Marion Island to identify changes in population trends. We contrasted five plausible trend models using information-theoretic and Bayesian-inference estimates of model parsimony. Our analyses identified two distinct phases of population growth for this population with the inflexion occurring in 1998. Thus, the population decreased between 1986 and 1997 (−3.7% per annum) and increased between 1997 and 2004 (1.9% per annum). An index of environmental stochasticity, the Southern Oscillation Index, explained some of the variance in r and N. We determined analytically that there was good evidence for density dependence in the Marion Island population and that density dependence was widespread among marine mammal species (67% of species showed evidence for population regulation). This approach demonstrates the potential functionality of a relatively simple technique that can be applied to short time series to identify the type of regulation, and the uncertainty associated with the phenomenon, operating in populations of large mammals.
Keywords demography
density dependence
climate change
Antarctica
Elephant seal
population change
mammal
DOI http://dx.doi.org/10.1007/s00442-008-1205-9   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
 
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