pants or units of effort in fisheries, is a related and serious problem. Open access to fisheries tends to favor overexploitation rather than stewardship, a common impediment to effective management (NRC, 1999b), although very few commercially important fisheries in North America and Europe are completely open access in the sense that most are regulated, some have limited entry, and many have restrictions on effort.1 Another problem is the failure of management to act expeditiously and conservatively or to respond appropriately. Ecosystem-based approaches to management (e.g., NMFS, 1999) have emerged from concern about bycatch, habitat destruction, and the failure to consider important biological interactions (e.g., predator-prey). Shortfalls in the ability of scientists to produce accurate stock assessments have at times provided poor advice to managers (NRC, 1998a, b). Stock assessments and resultant management measures always contain a level of uncertainty. To be effective in the face of this uncertainty requires that the assessments be interpreted conservatively so that stock size is not overestimated and subsequently overfished. Conservative, flexible, and adaptive approaches can compensate for the uncertainty of stock assessments, but frequently these features are lacking from conventional management.
Overfishing is in large part a consequence of excessive effort and capacity in fisheries (NRC, 1999a). Too often, fishery managers have been unable to control fishing effort, resulting in unsustainable levels of catch. This has been a particular problem for open-access fisheries where management does not limit the number of participants or high individual effort (see Chapter 4). In this situation, the economic incentives favor short-term exploitation over long-term sustainable use because the economic benefits of sacrificing current catch to rebuild the stock are intangible compared to short-term needs (bills to be paid), and long-term benefits may have to be shared with newcomers when the fishery recovers (Hilborn et al., in press). As more people enter the fishery or improve their fishing capabilities, the future yield to the individual fisher decreases. This often fosters competition to maintain or even increase individual catch levels even as stocks decline. In response, managers may shorten fishing seasons; participants then increase their fishing power, and effort becomes concentrated in time, sometimes resulting in “races for fish” or “fishing derbies.” In the worst cases, derbies are absurdly brief, lasting only two days in the Pacific halibut (Hippoglossus stenolepis) fishery in the United States during the early 1990s before individual quotas were implemented (NRC, 1999b).
In addition to depletion of fishery stocks, there are unintended consequences of fishing, such as bycatch and degradation of habitat from destructive fishing practices (Dayton et al., 1995; Watling and Norse, 1998). Bycatch here refers to