Optimal feeding and harvest time for fish with weight-dependent prices (original) (raw)

1998, Marine resource economics

Like agriculture, decisions regarding aquacultural production are complex. In addition to controlling harvest, feeding schedules, and culling rates, one must consider a number of practical considerations that may supersede other factors in economic importance. Among these pragmatic considerations are unusual aspects of the market price for fish. Fish markets provide premiums for larger-sized fish, and the premiums are often piecewise linear. This paper extends existing research by demonstrating general solutions for optimal feeding schedules and harvesting time under conditions of piecewise-continuous, weight-dependent prices. The solutions are characterized by idiosyncratic responses to marginal changes in exogenous parameters. For instance, a 1% decline in the interest rate can induce a 70% increase in the optimal weight. In general, as the interest rate decreases, optimal harvest weight and harvest time increase in a stepwise, nonlinear fashion. . Comments from Lars Olson, Camilo Sarmiento, and two anonymous reviewers are gratefully acknowledged. We also wish to thank Yana Christou, Demosthenes Ioannou, and his hospitable family for providing the sea bream production data. Funding for the project was provided by the Maryland Agricultural Experiment Station. 1 In this paper, we focus on the economics of open-system aquaculture. An open-system implies that not all of the biological parameters (i.e., water temperature, biological oxygen demand, etc.) affecting fish growth are controlled by the farmer. The following papers provide an economic analysis of closed system aquaculture: ; ). 2 Heaps (1993 followed up on the optimal control aquaculture model of Arnason. First, he derived a number of results concerning the effect of changes in various model parameters on the characteristics of the final harvest. Second, he extended the original model by allowing for density-dependent growth.