J. Hoekstra

Integrated models of fisheries management and policy

An overview of the structure and elements of integrated models aimed at studying fishery management policies using static and dynamic optimisation techniques is presented. Continuous and discrete time models are considered under both open-access and sole-owner settings. A variety of economic and biological processes that affect the fishery as a whole is examined. It turns out that overseeing important fish population characteristics such as metapopulation dynamics and multi-species interaction can lead to serious misrepresentation of the fishery and suboptimal controls. Adequate understanding of the economic conditions and considerations potentially affecting the fishermen is necessary to model their behaviour and address their concerns. Misrepresentation of these economic and biologic processes will have an impact on the success of management policies in attaining a sustainable fish population.

BIOECONOMIC ANALYSIS OF A SHELLFISHERY WITH HABITAT EFFECTS

In accordance with the recognition that fish populations generally are subject to complex dynamic population processes, there has been an increase over the last years in bioeconomic analysis that steps away from simple stock growth modeling techniques. Greater realism has been provided by modeling interdependency of fish species and by recognizing that fish species display different population dynamic characteristics at the adult life and recruitment life stages (Eggert, 1998). In line with these developments, the last decade has seen an increase in the literature focused on modeling sedentary fish population dynamics as metapopulations. The sedentary species considered in the literature generally have a life cycle consisting of a juvenile stage and an adult stage. In the juvenile stage, the species is dispersed throughout a specific predefined region. The species reaches an adult stage once the juvenile has found an appropriate location to settle, after which it is assumed to remain tied to the area. Previous model-based studies have analyzed the spatial population dynamics of the fish based on the ecological linkage to its surroundings (Possingham and Roughgarden, 1990; Alexander and Roughgarden, 1996), the metapopulation movements between a fishing ground and a marine reserve (Man et al., 1995) and the optimal way to exploit the fish species given certain metapopulation characteristics (Brown and Roughgarden, 1997; Bulte and van Kooten, 1999; Sanchirico and Wilen, 1999, 2001; Pezzey et al., 2000). In this chapter, a bioeconomic model is presented of a shellfishery where during each period juveniles are dispersed throughout the sea after adult spawning and, if possible, recruit to the shellfish bed. In each period, the effort exerted in order to catch shellfish is restricted. Fishing is only allowed to occur in the fishing season. The no-fishing season coincides with the adult spawning season. During this season, the newly born juvenile shellfish population is allowed to recruit. In the model discussed here, effort is assumed to have an indirect effect on recruitment, much as discussed by other bioeconomic models covering sedentary fish species, by reducing the adult fish population that can spawn and thus the size of the juvenile population that recruits to the fishery. As opposed to the general literature covering sedentary fish species, however, the model presented here goes one step further by assuming that effort exerted in order to catch shellfish