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effect of fishing before curtailing effort, to demonstrating that fishing practices will not damage the stock, habitat, or other ecosystem properties before allowing fishing to increase (Dayton et al., 1998). Although progress is slow, management is moving toward multispecies approaches, and ecosystem approaches eventually may be widely applied in managing marine fisheries (NMFS, 1999). Finally, the concept of embedding fishery management in the broader context of coastal zone management is being debated. It is here that MPAs can make an important contribution to accomplishing integrated management of our nation's coastal resources.

Long-term, single-species area closures represent a move toward MPA-style management. Although they have some features in common with reserves, single-species closures lack many key conservation benefits of permanent reserves and their objectives are generally narrowly drawn. Few temporal closures are designed to address multispecies or ecosystem concerns; rather temporal closures are a tool for single-species fishery management. An exception is the closure of areas 10-20 miles offshore of haulouts and rookeries occupied by endangered Steller sea lions (Eumetopias jubatus) to fishing for walleye pollock (Theragra chalcogramma). Other time and area restrictions have been implemented for the pollock fishery within and outside critical habitat for Steller sea lions.

UNCERTAINTY, FISHERY MANAGEMENT, AND A ROLE FOR MARINE RESERVES

Many scientists believe that a primary cause of fishery management failures is the inherent uncertainty in stock assessments. This uncertainty contributes to ineffective or untimely management actions and the reluctance of fishers to accept the economic costs of reducing effort even when stocks are in decline or their status is uncertain (Ludwig et al., 1993). To provide insurance against stock collapse, scientists have proposed establishing fishery reserves when the lack of accuracy in stock assessments and lack of resolve to fish conservatively make it difficult to achieve sustainable fishing levels under conventional management. The specific causes leading to the collapse of a fishery are controversial because it is difficult to discern the relative contributions of fishing pressure and environmental forces. Also, management generally does not account for the effect of environmental degradation on MSY (e.g., Myers et al., 1996, 1997; Orensanz and Jamieson, 1998; Caddy, 2000). Fishing fleets are ever more efficient at locating and catching remaining fish aggregations, with the result that once the fishery collapses, it may require long periods of time to recover, on the order of a decade or more, even in the absence of fishing (Hutchings, 2000). Ensuring against collapse is a primary but elusive goal of marine fishery management.

Central to the problem of uncertainty in fishery science and management is our difficulty in confronting it. Conventional fishery management relies on



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