The current worldwide crisis in marine fisheries can be summarized as “too many boats chasing too few fish.” In other words, many marine fisheries today suffer from a combination of overfishing of stocks and overcapacity of fishing fleets. Although fishing vessels can, and do, switch to new targets as current stocks become depleted, the world's oceans are finite. By the end of the 1990s the inevitable result was becoming apparent, as total worldwide catches of ocean fish (as reported by the United Nations Food and Agriculture Organization) began to decline. Documentation of this trend is provided by Pauly et al. (1998), Jackson et al. (2001), Hilborn et al. (2003), Myers and Worm (2003), Dulvy et al. (2003) and other publications. Based on large, detailed databases for world fisheries, these studies have demonstrated an unexpected degree of overharvesting, especially of large, valuable species.

Two important questions immediately arise. What are the underlying reasons for overfishing and overcapacity? What needs to be done to reverse the trend?

To begin with, it is obvious that economic forces are paramount—marine resources are exploited because of a demand for the product. If the revenue obtained from catching fish of a certain population exceeds the cost of doing so, there will exist an economic incentive to exploit that population. Unless the rate of harvesting can be controlled somehow, the fish population may eventually be reduced (at a profit) to a low level. This in turn may affect the productivity of the resource and greatly reduce future catches.