A spatial externality will result when the assumption of a homogeneously distributed resource is relaxed. In the presence of a heterogeneously distributed resource it is optimal for fisherman focus their effort in regions that possess the highest rates of immigration and substantially reduce their effort in areas that possess higher rates of emigration (Sanchirico and Wilen, 1999). A spatial externality will result when one over-harvests a region that possesses a bioeconomic link with the surrounding regions, thereby reducing the potential harvest in surrounding regions.