Publication Abstract

Increasing fisheries management options with a flexible cost function

P. Marchal and J.W. Horwood

This study proposes a dynamic control of fisheries by fishing effort, calculated so as to optimize a novel cost function, over a 20 years period of management, based upon an example of the exploitation of the Celtic Sea cod. This cost function is a flexible weighed compromise between: (i) minimizing the variability in fishing effort, (ii) minimizing the variability in yields, (iii) achieving an agreed fishing effort target, and (iv) achieving an agreed yield target. Increasing the weight on the criteria (ii) and (iii), and decreasing the weight on the criteria (i) and (iv), results in a more rapid movement of fishing effort towards the agreed long-term target, a decrease in short-term yields, and an increase in long-term yields. When the weight attached to (iii) is non-zero, the full optimization of the cost function provides a non-oscillatory, convergent, and near-linear control. When the weight attached to (iii) is zero, the full optimization of the cost function usually results in a non-linear divergent control, which is an artifact related to the choice of the length of the management period.

Reference:

P. Marchal and J.W. Horwood, 1998. Increasing fisheries management options with a flexible cost function. ICES Journal of Marine Science, 55: 213-227