A simple approach for dealing with dynamics and uncertainty in fisheries with heterogeneous resource and effort distribution

Abstract

Most fisheries models are based on dynamic pool assumptions. For sedentary and sessile species, these assumptions are inadequate, because they are spatially distributed in patches that vary in size, density and age structure. A simple bioeconomic model, negative binomial (NEGBIN), is proposed; this model relaxes the dynamic pool assumption without entering into the complexities of a geographically structured model. NEGBIN assumes a probability density function (the negative binomial), to describe heterogeneity in the density distribution over the population range. The model incorporates decision theory and different levels of risk aversion in resource management. The uncertainty associated with alternative fishing strategies, given imperfect knowledge about virgin stock biomass, is also included in the analysis. The model is applied to the Mesodesma donacium (surf clam) fishery in the central northern zone of Chile (South America). Alternative management strategies are evaluated with different levels of risk aversion. In the fisheries literature to date, this approach to evaluating the uncertainty associated with spatial allocation decisions has been rare. It is suggested that this kind of analysis, whether accompanied by quantitative probabilities of alternative states of nature or not, is an alternative way of dealing with risk and uncertainty in spatial allocation decisions.