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Predicting the impact of stage-specific harvesting on population dynamics

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Carslake, David, Townley, Stuart and Hodgson, David J.. (2009) Predicting the impact of stage-specific harvesting on population dynamics. Journal of Animal Ecology, Vol.78 (No.5). pp. 1076-1085. ISSN 0021-8790

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Official URL: http://dx.doi.org/10.1111/j.1365-2656.2009.01569.x

Abstract

Perturbation analyses of population projection matrices predict the response of a population's growth rate to changes in lifestage-specific vital rates. Such predictions have been widely used in population management but their reliability remains hotly debated.

We grew replicate populations of the water flea Daphnia magna in controlled, density-independent conditions and subjected treatment populations to harvesting of the largest lifestage. We predicted the growth rate of treatment populations using sensitivity analysis (a linear approximation), and transfer function analysis (TFA; which captures nonlinear responses) applied to projection matrix models parameterized from the control populations.

When perturbation analyses considered only the direct effect of harvesting on adult survival, the growth rate of harvested populations (averaging 0 center dot 051) was significantly overestimated (average of 0 center dot 112) by TFA and non-significantly underestimated (average of 0 center dot 012) by sensitivity.

When the indirect effects of harvesting on other vital rates were accounted for in a structured perturbation, TFA gave accurate predictions (average growth rate of 0 center dot 068), while sensitivity gave significant underestimates (average of -0 center dot 043).

Our results demonstrate two crucial sources of error that may influence predictions of the impacts of demographic perturbations on population dynamics. First, impacts of stage-specific harvesting are inherently nonlinear, hence predictions based on sensitivity must be treated with caution. Second, stage-specific perturbations can change non-target demographic rates, even in the absence of adaptation.

Population managers should consider both nonlinear and indirect effects of perturbations when designing management interventions. We encourage the development of methods to assess the robustness of predictions to unforeseen perturbation structures and indirect harvesting impacts.

Item Type:

Journal Article

Subjects:

Q Science > QH Natural history > QH301 Biology
Q Science > QL Zoology

Divisions:

Faculty of Science > Life Sciences (2010- ) > Biological Sciences ( -2010)

Journal or Publication Title:

Journal of Animal Ecology

Publisher:

Wiley-Blackwell Publishing Ltd.

ISSN:

0021-8790