, Volume 54, Issue 1, pp 139-154

Selectivity, Pulse Fishing and Endogenous Lifespan in Beverton-Holt Models

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Abstract

Optimal management in a multi-cohort Beverton-Holt model with any number of age classes and imperfect selectivity is equivalent to finding the optimal fish lifespan by chosen fallow cycles. Optimal policy differs in two main ways from the optimal lifespan rule with perfect selectivity. First, weight gain is valued in terms of the whole population structure. Second, the cost of waiting is the interest rate adjusted for the increase in the pulse length. This point is especially relevant for assessing the role of selectivity. Imperfect selectivity reduces the optimal lifespan and the optimal pulse length. We illustrate our theoretical findings with a numerical example. Results obtained using global numerical methods select the optimal pulse length predicted by the optimal lifespan rule.

This paper has benefited from comments and suggestions by the Editor, David Finnoff, and two anonymous referees. We are especially grateful to Rögnvaldur Hannesson, Anders Skonhoft, Olli Tahvonen, and seminar participants at the First Age-structured Models in Fishery Economics and Bio-economic Modeling Workshop, held in Trondheim, Norway on 12–13 August 2009 and the participants in the Lisbon and Brussels 2007 Northern Hake Working Group meetings. Financial aid from the European Commission (MYFISH, FP7-KBBE-2011-5), the Spanish Ministry of Science and Innovation (ECO2009-14697-C02-01 and 02) and the Xunta de Galicia (Anxeles Alvariño programme) is gratefully acknowledged. The first draft of the paper was written while Jose Maria Da Rocha was visiting Institut d’Anà lisi Econòmica-CSIC. He gratefully acknowledges its hospitality.