Optimal Harvesting Problem Research Articles

Optimal Harvesting for a Logistic Population Dynamics Driven by a Lévy Process

The optimal harvesting problem for a stochastic logistic jump-diffusion process is studied in this paper. Two kinds of environmental noises are considered in the model. One is called white noise wh...

Optimal Management of a Renewable Resource Subjected to Strong Allee effect in a Periodically Fluctuating Environment

In this article we present the qualitative properties of solutions of a periodic differential equation that describes dynamics of a renewable resource subjected to strong Allee effect (multiplicative Allee effect) with periodic harvesting in a periodically fluctuating environment. We also present the bio-economic aspects of the considered renewable resource studied from sole owner perspective. An optimal harvesting problem with periodic dynamic constraints has been solved using Pontryagin’s maximum principle. It is interesting to find that the considered optimal control problem admits multiple periodic singular solutions. Techniques are developed to identify the optimal singular solution and the associated optimal singular periodic effort function. Optimal, suboptimal harvest policies and their corresponding approach paths are constructed. It is found that the optimal harvest policies are periodic after some time.

OVERTAKING OPTIMAL HARVESTING FOR AN AGE-DEPENDENT n-DIMENSIONAL FOOD CHAIN MODEL

This paper is concerned with an optimal harvesting problem over an infinite horizon for age-dependent n-dimensional food chain model and the analysis of long-term behaviors of the optimal-controlled system. The existence of overtaking optimal policy is proved and a maximum principle is carefully derived by means of Dubovitskii–Milyutin functional analytical extremum theory. Weak and strong turnpike properties of optimal trajectories are established.

Global stability and bifurcation analysis of a delay induced prey-predator system with stage structure

This paper describes a delay induced prey–predator system with stage structure for prey. The dynamical characteristics of the system are rigorously studied using mathematical tools. The coexistence equilibria of the system is determined and the dynamic behavior of the system is investigated around coexistence equilibria. Sufficient conditions are derived for the global stability of the system. The optimal harvesting problem is formulated and solved in order to achieve the sustainability of the system, keeping the ecological balance, and maximize the monetary social benefit. Maturation time delay of prey is incorporated and the existence of Hopf bifurcation phenomenon is examined at the coexistence equilibria. It is shown that the time delay can cause a stable equilibrium to become unstable and even a switching of stabilities. Moreover, we use normal form method and center manifold theorem to examine the nature of the Hopf bifurcation. Finally, some numerical simulations are given to verify the analytical results, and the system is analyzed through graphical illustrations.

The optimal harvesting policy for non-autonomous populations with discount

Infinite horizon and non-autonomous optimal harvesting problems with discounted instantaneous utility are considered in this work. We first show that the optimal harvesting policy exists for a class of single populations by using the maximum principle. Second, the explicit expressions for the optimal harvesting policy and the maximum yields of logistic, Gompertz and Gilpin–Ayahs systems are obtained.

Ergodic method on optimal harvesting for a stochastic Gompertz-type diffusion process

In this paper, the stochastic harvesting problem is regarded as a mathematical formulation of finding the maximum sustained yield and the corresponding best sustainable harvesting strategies under uncertainty. We use a new method to solve this problem, and prove the equivalency between this method and previous methods. This paper is the first attempt to apply the ergodic theory on the optimal harvesting problem, to the best of our knowledge.

BANG-BANG, IMPULSE, AND SUSTAINABLE HARVESTING IN AGE-STRUCTURED POPULATIONS

An optimal harvesting problem is analyzed in the Lotka–McKendrick model of age-structured populations. Depending on the imposed constraints, this problem possesses bang-bang or impulse regimes, which have meaningful interpretations and relevant policy implications. A steady state analysis of the model produces closed-form solutions for the optimal sustainable harvesting in a new and an existing population.

Numerical Optimal Harvesting for an Age-Dependent Prey-Predator System

In this article, we develop a numerical study of an optimal harvesting problem for age-dependent prey-predator system. Here, the rates of growth and decay as well as the interaction effect between species are assumed to be depending on age, time and space. Existence, uniqueness, and necessary conditions for the optimal control are assured in case of a small final time T. The discrete parabolic nonlinear dynamical systems are obtained by using a finite difference semi-implicit scheme. Then a numerical algorithm is developed to approximate the optimal harvesting effort and the optimal harvest. Results of the numerical tests are given.

Malliavin calculus applied to optimal control of stochastic partial differential equations with jumps

In this paper, we employ Malliavin calculus to derive a general stochastic maximum principle for stochastic partial differential equations with jumps under partial information. We apply this result to solve an optimal harvesting problem in the presence of partial information. Another application pertains to portfolio optimization under partial observation.

Optimal harvesting and planting control in stochastic logistic population models

We consider the optimal harvesting and planting control problem to maximize the expected total net benefits in the stochastic logistic population model. The variational inequality associated with this problem is given by the degenerate form of elliptic type with quadratic coefficients. Using the viscosity solutions technique, we solve the corresponding penalty equation and show the existence of a solution to the variational inequality. The optimal harvesting and planting policy is characterized in terms of two thresholds for the variational inequality.

The Impact of Stochastic Convenience Yield on Long-Term Forestry Investment Decisions

This paper investigates whether convenience yield is an important factor in determining optimal decisions for a forestry investment. The Kalman filter method is used to estimate three different models of lumber prices: a mean reverting model, a simple geometric Brownian motion and the two-factor price model due to Schwartz (1997). In the latter model there are two correlated stochastic factors: spot price and convenience yield. The two-factor model is shown to provide a reasonable fit of the term structure of lumber futures prices. The impact of convenience yield on a forestry investment decision is examined using the Schwartz (1997). long-term model which transforms the two-factor price model into a single factor model with a composite price. Using the long-term model an optimal harvesting problem is analyzed, which requires the numerical solution of a Hamilton-Jacobi-Bellman equation. We compare the results for the long-term model to those from single-factor mean reverting and geometric Brownian motion models. The inclusion of convenience yield through the long-term model is found to have a significant impact on land value and optimal harvesting decisions.

Regime switching in stochastic models of commodity prices: An application to an optimal tree harvesting problem

This paper investigates whether a regime switching model of stochastic lumber prices is better for the analysis of optimal harvesting problems in forestry than a more traditional single regime model. Prices of lumber derivatives are used to calibrate a regime switching model, with each of two regimes characterized by a different mean reverting process. A single regime, mean reverting process is also calibrated. The value of a representative stand of trees and optimal harvesting prices are determined by specifying a Hamilton–Jacobi–Bellman Variational Inequality, which is solved for both pricing models using a implicit finite difference approach. The regime switching model is found to more closely match the behavior of futures prices than the single regime model. In addition, analysis of a tree harvesting problem indicates significant differences in terms of land value and optimal harvest thresholds between the regime switching and single regime models.

On Optimal Harvesting Problems in Random Environments

This paper investigates the optimal harvesting strategy for a single species living in random environments whose growth is given by a regime-switching diffusion. Harvesting acts as a (stochastic) control on the size of the population. The objective is to find a harvesting strategy which maximizes the expected total discounted income from harvesting {\em up to the time of extinction} of the species; the income rate is allowed to be state- and environment-dependent. This is a singular stochastic control problem with both the extinction time and the optimal harvesting policy depending on the initial condition. One aspect of receiving payments up to the random time of extinction is that small changes in the initial population size may significantly alter the extinction time when using the same harvesting policy. Consequently, one no longer obtains continuity of the value function using standard arguments for either regular or singular control problems having a fixed time horizon. This paper introduces a new sufficient condition under which the continuity of the value function for the regime-switching model is established. Further, it is shown that the value function is a viscosity solution of a coupled system of quasi-variational inequalities. The paper also establishes a verification theorem and, based on this theorem, an $\varepsilon$-optimal harvesting strategy is constructed under certain conditions on the model. Two examples are analyzed in detail.

OVERTAKING OPTIMAL HARVESTING OF AGE-STRUCTURED PREDATOR-PREY SYSTEMS

This article is concerned with an optimal harvesting problem over an infinite horizon for age-dependent predator-prey system and the analysis of long-term behaviors of the optimal-controlled system. Instead of usual concepts, overtaking (or catching-up) optimality is adopted. First-order necessary conditions for optimal controller are carefully derived by means of Dubovitskii–Milyutin functional analytical extremum theory, which differs from the Lagrangian multipliers and the variation of calculus. Another focus of the article is the investigation of turnpike properties of population densities. Our results demonstrate the convergence of the optimal trajectories to an equilibrium in the sense of integral average, weak and point-wise, respectively. This research extend the results for linear equations of single species to situations of interacting species, and provide a unified framework for the treatment of multi-dimensional problems.

A Limit Harvesting Problem of Population Dynamics with Logistic Term

In this paper, a nonlinear age-dependent population model with logistic term is considered. In the first part is reminded a large time behavior result, and next an optimal harvesting problem associated to a limit problem is investigated. Existence of an optimal control and necessary optimality conditions are established. Mathematics Subject Classication 2000: 35B40, 49J15, 92D25.

Optimal harvesting for periodic age-dependent population dynamics with logistic term

We prove an asymptotic behavior result for an age-dependent population dynamics with logistic term and periodic vital rates. We investigate next an optimal harvesting problem related to a periodic age-structured model with logistic term. Existence of an optimal control and necessary optimality conditions are established. A conceptual algorithm to approximate the optimal pair is derived and some numerical experiments are presented.

Control problems of an age-dependent predator-prey system

This paper is concerned with optimal harvesting problems for a system consisting of two populations with age-structure and interaction of predator-prey. Existence and uniqueness of non-negative solutions to the system and the continuous dependence of solutions on control variables are investigated. Existence of optimal policy is discussed, optimality conditions are derived by means of normal cone and adjoint system techniques.

Numerical Optimal Harvesting for a Periodic Age-Structured Population Dynamics with Logistic Term

We investigate an optimal harvesting problem for age-structured population dynamics with logistic term and periodic vital rates. We use first-order necessary optimality conditions in order to derive an algorithm to approximate the optimal harvesting effort. We present corresponding numerical experiments.

OPTIMAL HARVESTING OF A SPATIALLY EXPLICIT FISHERY MODEL

Abstract We consider an optimal fishery harvesting problem using a spatially explicit model with a semilinear elliptic PDE, Dirichlet boundary conditions, and logistic population growth. We consider two objective functionals: maximizing the yield and minimizing the cost or the variation in the fishing effort (control). Existence, necessary conditions, and uniqueness for the optimal harvesting control for both cases are established. Results for maximizing the yield with Neumann (no‐flux) boundary conditions are also given. The optimal control when minimizing the variation is characterized by a variational inequality instead of the usual algebraic characterization, which involves the solutions of an optimality system of nonlinear elliptic partial differential equations. Numerical examples are given to illustrate the results.

HARVESTING AN AGE‐STRUCTURED POPULATION AS BIOMASS: DOES IT WORK?

AbstractThe economics of fisheries is based heavily on describing fish populations by the surplus production model. Both economists and ecologists have different opinions on whether this approach provides an adequate biological basis for economic analysis. This study takes an age‐structured population model and shows how, under equilibrium conditions, it determines the surplus production model. The surplus production model is then used to solve an optimal feedback policy for a generic optimal harvesting problem. Next, it is assumed that the fishery manager applies this feedback policy even though the fish population actually evolves according to the age‐structured model. This framework is applied to the widow rockfish, Atlantic menhaden, and Pacific halibut fisheries. Population age‐structure contains information on future harvest possibilities. The surplus production model neglects this information and may lead to major deviations between the expected and actual outcomes especially under multiple steady states and nonlinearities.