Simple fishery and marine reserve models to study the sloss problem

Abstract

Habitat fragmentation is generally believed to be detrimental to the persistence of natural populations. In nature management one therefore tends to prefer many small nature reserves over one single large having equal total area. The paper presents two tractable analytical models to examine whether this preference is warranted in a metapopulation framework with reserves (patches) by formulating the dependence of the density as well as the global catch on the number of reserves. Studying these models, we seek to compare the two different strategies: whether a single large reserve will (1) conserve more species and (2) maintains high yield in fisheries than several small or vice versa? Our results indicate that it is favourable to make several small reserves instead one single large reserve. Indeed, at equilibrium, the density as well as the global catch are bigger in the Several Small (SS) strategy than in the Single Large (SL) one. In addition, in the case of SS strategy, an intermediate reserve number exists which is optimal for catch at equilibrium. The results in this paper may provide important implications for nature conservation.