Blar i forfatter "Wyller, John Andreas"

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    • Accumulated marine pollution and fishery dynamics 

      Bergland, Harald; Pedersen, Pål Andreas; Wyller, John Andreas (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-05)
      We analyze the possible impacts of pollution on a fishery by means of a dynamical systems theory approach. The proposed model presupposes that activities stimulating economic growth also cause higher emissions that remediate or accumulate in the oceans. The density of pollution is assumed to affect the fishery negatively by reducing biological growth potential and decreasing marginal willingness to ...

    • Aquaculture, pollution and fishery - dynamics of marine industrial interactions 

      Bergland, Harald; Burlakov, Evgenii; Pedersen, Pål Andreas; Wyller, John Andreas (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-10)
      We model bioeconomic interrelations between a commercial fishery and an aquaculture industry by using a dynamical systems theory approach. The biomass follows a logistic growth where the pollution emerging from aquaculture is accounted for by means of a retardation term. We investigate the existence and stability of the equilibrium states of this model as a function of the growth-retardation parameter ...

    • The Dynamics of Pasture–Herbivores–Carnivores with Sigmoidal Density Dependent Harvesting 

      Bergland, Harald; Burlakov, Evgenii; Wyller, John Andreas (Journal article; Tidsskriftartikkel, 2023-09-19)
      We investigate biomass–herbivore–carnivore (top predator) interactions in terms of a tritrophic dynamical systems model. The harvesting rates of the herbivores and the top predators are described by means of a sigmoidal function of the herbivores density and the top predator density, respectively. The main focus in this study is on the dynamics as a function of the natural mortality and the maximal ...

    • Pasture-livestock dynamics with density-dependent harvest and changing environment 

      Bergland, Harald; Wyller, John Andreas; Burlakov, Evgenii (Journal article; Tidsskriftartikkel, 2019-02-19)
      We model pasture–livestock interactions by means of a predator–prey model, with the biomass vegetation as prey and the herbivores as predators. The harvesting rate is a sigmoidal function of the livestock density. We identify the necessary biological and harvest conditions for different equilibria of this model to exist. The system possesses no interior equilibrium points for the mortality rate ...

    • Stable and unstable equilibrium states in a fishery-aquaculture model 

      Bergland, Harald; Pedersen, Pål Andreas; Wyller, John Andreas (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-20)
      We study interactions between fishery and aquaculture using a 3D generalized Lotka–Volterra model, where we assume that the aquaculture production may affect the growth rate in the fish stock and the productivity in harvesting. In addition, input demands from both marine industries may result in effort competition. We identify conditions for the coexistence of a unique equilibrium state inside the ...