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The role of harvesting in age-structured populations: Disentangling dynamic and age truncation effects

Wikström, Anders LU ; Ripa, Jörgen LU and Jonzén, Niclas LU (2012) In Theoretical Population Biology 82(4). p.348-354
Abstract
Understanding the processes generating fluctuations of natural populations lies at the very heart of academic ecology. It is also very important for applications such as fisheries management and pest control. We are interested in the effect of harvesting on population fluctuations and for that purpose we develop and analyze an age-structured model where recruitment is a stochastic process and the adult segment of the population is harvested. When a constant annual harvest is taken the coefficient of variation of the adult population increases for most parameter values due to the age truncation effect, i.e. an increased variability in a juvenescent population due to the removal of older individuals. However, if a constant proportion of the... (More)
Understanding the processes generating fluctuations of natural populations lies at the very heart of academic ecology. It is also very important for applications such as fisheries management and pest control. We are interested in the effect of harvesting on population fluctuations and for that purpose we develop and analyze an age-structured model where recruitment is a stochastic process and the adult segment of the population is harvested. When a constant annual harvest is taken the coefficient of variation of the adult population increases for most parameter values due to the age truncation effect, i.e. an increased variability in a juvenescent population due to the removal of older individuals. However, if a constant proportion of the adults is harvested the age truncation effect is sometimes counteracted by a stabilizing dynamic effect of harvesting. Depending on parameter values mirroring different life histories, proportional harvest can either increase or decrease the relative fluctuations of an exploited population. When there is a demographic Allee effect the ratio of juveniles to adults may actually decrease with harvesting. We conclude that, depending on life history and harvest strategy, harvesting can either reinforce or dampen population fluctuations due to the relative importance of stabilizing dynamic effects and the age truncation effect. The strength of the latter is highly dependent on the fished population's endogenous, age-structured dynamics. More specifically, we predict that populations with strong and positively autocorrelated dynamics will show stronger age truncation effect, a testable prediction that offers a simple rule-of-thumb assessment of a population's vulnerability to exploitation. (C) 2011 Elsevier Inc. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Harvest theory, Age-structure, Fishing, Stochasticity, Variability, Age-truncation effect
in
Theoretical Population Biology
volume
82
issue
4
pages
348 - 354
publisher
Academic Press
external identifiers
  • wos:000311981400012
  • scopus:84869857562
ISSN
1096-0325
DOI
10.1016/j.tpb.2011.12.008
language
English
LU publication?
yes
id
e2cc14fb-f3e4-4213-9fac-18842f13ab4f (old id 3372519)
date added to LUP
2013-02-01 13:18:31
date last changed
2017-11-19 03:46:42
@article{e2cc14fb-f3e4-4213-9fac-18842f13ab4f,
  abstract     = {Understanding the processes generating fluctuations of natural populations lies at the very heart of academic ecology. It is also very important for applications such as fisheries management and pest control. We are interested in the effect of harvesting on population fluctuations and for that purpose we develop and analyze an age-structured model where recruitment is a stochastic process and the adult segment of the population is harvested. When a constant annual harvest is taken the coefficient of variation of the adult population increases for most parameter values due to the age truncation effect, i.e. an increased variability in a juvenescent population due to the removal of older individuals. However, if a constant proportion of the adults is harvested the age truncation effect is sometimes counteracted by a stabilizing dynamic effect of harvesting. Depending on parameter values mirroring different life histories, proportional harvest can either increase or decrease the relative fluctuations of an exploited population. When there is a demographic Allee effect the ratio of juveniles to adults may actually decrease with harvesting. We conclude that, depending on life history and harvest strategy, harvesting can either reinforce or dampen population fluctuations due to the relative importance of stabilizing dynamic effects and the age truncation effect. The strength of the latter is highly dependent on the fished population's endogenous, age-structured dynamics. More specifically, we predict that populations with strong and positively autocorrelated dynamics will show stronger age truncation effect, a testable prediction that offers a simple rule-of-thumb assessment of a population's vulnerability to exploitation. (C) 2011 Elsevier Inc. All rights reserved.},
  author       = {Wikström, Anders and Ripa, Jörgen and Jonzén, Niclas},
  issn         = {1096-0325},
  keyword      = {Harvest theory,Age-structure,Fishing,Stochasticity,Variability,Age-truncation effect},
  language     = {eng},
  number       = {4},
  pages        = {348--354},
  publisher    = {Academic Press},
  series       = {Theoretical Population Biology},
  title        = {The role of harvesting in age-structured populations: Disentangling dynamic and age truncation effects},
  url          = {http://dx.doi.org/10.1016/j.tpb.2011.12.008},
  volume       = {82},
  year         = {2012},
}