Sustainable fisheries

摘要

The destruction of the worlds major fisheries has been widely documented, with a general consensus that the biomass of top marine predators is now some 10% of what it was half a century ago. Many of these species - such as the bluefin tuna, Atlantic cod, and sword-fish in the Atlantic and Indian oceans - are expected to be extinct within decades. There is therefore great interest in finding ways of managing fisheries that ensure their sustainable use, allowing a fish population to return to earlier levels and providing a secure basis for a healthy and profitable fishery. Writing in Science, Cos-tello, Gaines and Lynham present a convincing and thorough analysis of this issue. They suggest that a particular management approach, the use of 'individual tradable quotas' (ITQs), has had dramatically beneficial impacts on many of the fisheries in which they have been implemented. The destruction of the worlds fisheries is a classic illustration of the 'tragedy of the commons'. With open access, all boats are competing for the same fish: the more fish one catches, the fewer there are for others. Everyone rushes to catch as many as possible. There is no point in leaving fish untouched so they can breed, as competitors will catch them. Economists have developed formal models showing that the outcome is a massive overuse relative to the policy that would generate the greatest economic value from the fishery.