Discussion Papers, Department of Business and Management Science, Norwegian School of Economics (NHH)
Optimal fishing mortalities with age-structured bioeconomic model - a case of NEA mackerel
() and Stein I. Steinshamn
Abstract: The effects of random environmental impacts on optimal
exploitation of a fish population are investigated using both optimization
and simulation, based on a discrete-time age-structured bioeconomic model.
The optimization problem is solved as a non-linear programming problem in
GAMS. First, a basic model structure and 6 different scenarios, dealing
with two interactions between fish and environment, are introduced. Based
on the simplest scenario, eight different parameter combinations are
tested. Then the optimization problem is solved for each of the 6 scenarios
for a period of 100 years in order to gain long term insights. The main
finding is that higher volatility from the environment leads to higher net
profits but together with a lower probability of actually hitting the mean
values. Simulations are conducted with different fixed fishing mortality
levels under 6 scenarios. It seems that a constant fishing mortality around
0.06 is optimal. In the end, a comparison is made between historical and
optimal harvest for a period of 40 years. It turns out that in more than
70% of the time, the optimal exploitation offered by our optimization model
dominates the historical one, leading to 43% higher net profit and 34%
lower fishing cost on average.
Keywords: Random environmental impacts; optimal exploitation; non-linear programming; (follow links to similar papers)
JEL-Codes: C61; Q00; Q20; Q22; Q50; (follow links to similar papers)
25 pages, May 31, 2016
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