<p>In this work we study a Lotka–Volterra predator-prey system in which the predator population is subjected to a discontinuous harvesting action that depends on the prey abundance. In this case the harvesting is activated when the prey level falls below a critical value <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(x_r\)</EquationSource> </InlineEquation> and deactivated otherwise, giving rise to a two-dimensional piecewise-smooth differential system whose switching boundary is <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(x = x_r\)</EquationSource> </InlineEquation>. Assuming constant growth rates, with <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(g(x) = a \in \mathbb {R}^+\)</EquationSource> </InlineEquation> for the prey and <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(f(x) = f \in \mathbb {R}^+\)</EquationSource> </InlineEquation> for the predator, and a Holling type II functional response, we perform a complete analysis of the phase portraits in the Poincaré disc. The qualitative behavior of the trajectories depends on the parameters <i>a</i> and <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\mu = f - d\)</EquationSource> </InlineEquation> (where <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(d&gt;0\)</EquationSource> </InlineEquation> is the predator mortality). The adopted harvesting strategy does not allow the stabilization of the prey and predator populations at the desired value <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(x = x_r.\)</EquationSource> </InlineEquation> Moreover it is proven that the system does not exhibit limit cycles. Finally numerical simulations illustrate the distinct global configurations.&#xa0;&#xa0;&#xa0;&#xa0;</p>

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Phase Portraits of a Lotka-Volterra Model with Discontinuous Harvesting Action

  • Marly T. A. Cabrera,
  • Rony Cristiano,
  • Jaume Llibre

摘要

In this work we study a Lotka–Volterra predator-prey system in which the predator population is subjected to a discontinuous harvesting action that depends on the prey abundance. In this case the harvesting is activated when the prey level falls below a critical value \(x_r\) and deactivated otherwise, giving rise to a two-dimensional piecewise-smooth differential system whose switching boundary is \(x = x_r\) . Assuming constant growth rates, with \(g(x) = a \in \mathbb {R}^+\) for the prey and \(f(x) = f \in \mathbb {R}^+\) for the predator, and a Holling type II functional response, we perform a complete analysis of the phase portraits in the Poincaré disc. The qualitative behavior of the trajectories depends on the parameters a and \(\mu = f - d\) (where \(d>0\) is the predator mortality). The adopted harvesting strategy does not allow the stabilization of the prey and predator populations at the desired value \(x = x_r.\) Moreover it is proven that the system does not exhibit limit cycles. Finally numerical simulations illustrate the distinct global configurations.