Authors: Arild Wikan
Publish Date: 2004/01/02
Volume: 49, Issue: 1, Pages: 35-55
Abstract
The role of harvest in discrete agestructured onepopulation models has been explored Considering a few age classes only together with the overcompensatory Ricker recruitment function we show that harvest acts as a weak destabilizing effect in case of small values of the yeartoyear survival probability P and as a strong stabilizing effect whenever the survival probability approaches unity In the latter case assuming n=2 age classes we find that harvest may transfer a population from the chaotic regime to a state where the equilibrium point x1 x2 becomes stable However as the number of age classes increases which acts as a stabilizing effect in nonexploited models we find that harvest acts more and more destabilizing in fact when the number of age classes has been increased to n=10 our finding is that in case of large values of the survival probabilities harvest may transfer a population from a state where the equilibrium is stable to the chaotic regime thus exactly the opposite of what was found in case of n=2 On the other hand if we replace the Ricker relation with the generalized Beverton and Holt recruitment function with abruptness parameter larger than 2 several of the conclusions derived above are changed For example when n is large and the survival probabilities exceed a certain threshold the equilibrium will always be stable
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