Long Chu

Maximum economic yield

Analytical results for steady-state values of the biomass that maximises the sum of inter-temporal economic profits (dynamic bMEY) are derived in terms of a generalised harvesting function. The conditions under which dynamic bMEY exceeds the biomass that maximises the sustained yield (bMSY) are evaluated under a range of conditions including when the discount rate exceeds the intrinsic growth rate, with a variable stock effect, technological change, and from an increase in the cost per unit of effort. The findings show that dynamic bMSY provides both a sustainable and profitable management target under a wide range of parameter values.

Comparing approximation techniques to continuous-time stochastic dynamic programming problems: Applications to natural resource modelling

Dynamic programming problems are common in economics, finance and natural resource management. However, exact solutions to these problems are exceptional. Instead, solutions typically rely on numerical approximation techniques which vary in use, complexity and computational requirements. Perturbation, projection and linear programming approaches are among the most useful of these numerical techniques. In this paper, we extend the parametric linear programming technique to include continuous-time problems with jump-diffusion processes, and compare it to projection and perturbation techniques for solving dynamic programming problems in terms of computational speed, accuracy, ease of use and scope. The comparisons are drawn from solutions to two fisheries management problems - a unidimensional model of optimal harvest and a multidimensional model for optimal marine reserve size. Available computer code illustrates how each technique solves these problems and how they can be applied to other comparable problems in natural resource modelling.