Economic incentives and overfishing: a bioeconomic vulnerability index.

Bioeconomic theory predicts that the trade-offs between maximization of economic benefits and conservation of vulnerable marine species can be assessed using the ratio between the discount rate of fishers and the intrinsic rate of growth of the exploited populations. In this paper, we use this theory to identify areas of the global ocean where higher vulnerability of fishes to overfishing would be expected in the absence of management. We derive an index to evaluate the level of vulnerability by comparing discount rates and fishes’ intrinsic population growth rates. Using published discount rates of countries that are reported to fish in the ocean and estimating the intrinsic population growth rate for major exploited fishes in the world, we calculate the vulnerability index for each 0.5° latitude × 0.5° longitude grid for each taxon and each fishing country.