Experimental evidence of size-selective harvest and environmental stochasticity effects on population demography,fluctuations and non-linearity |
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Authors: | Luke A Rogers Zachary Moore Abby Daigle Pepijn Luijckx Martin Krko?ek |
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Institution: | 1. Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada;2. Gulf Fisheries Centre, Fisheries and Oceans Canada, Moncton, New Brunswick, Canada;3. Department of Zoology, School of Natural Sciences, Trinity College Dublin, College Green, Dublin 2, Dublin, Ireland |
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Abstract: | Theory and analyses of fisheries data sets indicate that harvesting can alter population structure and destabilise non-linear processes, which increases population fluctuations. We conducted a factorial experiment on the population dynamics of Daphnia magna in relation to size-selective harvesting and stochasticity of food supply. Harvesting and stochasticity treatments both increased population fluctuations. Timeseries analysis indicated that fluctuations in control populations were non-linear, and non-linearity increased substantially in response to harvesting. Both harvesting and stochasticity induced population juvenescence, but harvesting did so via the depletion of adults, whereas stochasticity increased the abundance of juveniles. A fitted fisheries model indicated that harvesting shifted populations towards higher reproductive rates and larger-magnitude damped oscillations that amplify demographic noise. These findings provide experimental evidence that harvesting increases the non-linearity of population fluctuations and that both harvesting and stochasticity increase population variability and juvenescence. |
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Keywords: | Daphnia magna delay embedding empirical dynamic modelling fishery model-free forecasting non-linear deterministic process oscillations population dynamics stability |
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