EVALUATING TUNA MANAGEMENT IN THE EASTERN PACIFIC OCEAN

摘要

We answer four questions about tuna management in the eastern Pacific Ocean: What are the management objectives? Are they reasonable? Can we determine whether they have been achieved? Have they been achieved? There are explicit, overarching management objectives including keeping populations at levels that will permit maximum sustainable yields, consideration of the precautionary approach, and consideration of ecosystem consequences, but although reasonable, these objectives are vague from a stock-assessment perspective. Objectives of individual participants are unlikely to be the same and collectively make achieving the overarching objectives more difficult. For data-rich stocks, we can determine whether the yield-based objectives have been achieved, but even these results have alternative interpretations. Unfortunately, when data are limited, the management objectives cannot be evaluated. In the eastern Pacific, species differ in achievement of objectives. Yield-based objectives are probably being achieved for yellowfin tuna—yields may increase if effort is reallocated among fishing methods—whereas for bigeye tuna, biomass levels are falling below that necessary for maximum sustainable yield. For skipjack, although the population level is healthy, restrictions designed to protect bigeye and yellowfin tuna prevent fishermen from achieving maximum sustainable yield. By-catch of other species in the tuna fisheries is a management concern.