With the biomass of the world's top marine predators at about a tenth of what it was in the 1950s, fisheries need management that will stop them collapsing. In September, Christopher Costello of the University of California, Santa Barbara, and his colleagues used data from 1950 to 2003 and 11,135 fisheries to conclude that individual tradable quotas (ITQs) could help.
ITQs avoid the misaligned incentives of the 'tragedy of the commons' whereby people plunder resources as quickly as possible. The quotas divide a limited total catch exclusively among fishermen who work a fishery, and allow them to sell the rights to their share. Because the value of these shares increases with the overall productivity of the fishery, each fisherman has an incentive to manage it well. Costello's team found that the proportion of ITQ-managed fisheries that had collapsed by 2003 was half that of the non-ITQ fisheries.