The tragedy of the (anti-)commons: The case of prey-predator fisheries

We examine the efficiency and environmental consequences of assigning species-specific common-property rights, considering a Lotka-Volterra model in which fisheries are specialized in the harvesting of a single species. We show that the fragmentation of the ecosystem implies the tragedy of the anticommons even when fisheries compete for the resource. Indeed, contrasting the private exploitation equilibrium with the socially optimal solution, we demonstrate that the predator stock is too high while the prey stock is too low under private property rights. A puzzling result is that the "abundant" species is actually underused because of insufficient economic incentives; however, the scarce and high-priced species does not necessarily suffer from overexploitation. Biological interactions are consequently the main driver of stock depletion. Finally, we investigate how to simultaneously solve both the tragedy of the commons and that of the anticommons and analyze the economic costs of regulating only the tragedy of the commons.