Precautionary harvest policies and the uncertainty paradox

Elements of the precautionary approach to fishery management are commonly implemented in the form of harvest control rules, with limit, threshold and target reference points for stock size and fishing mortality. However, a review of two large advisory and management systems indicates that many stock assessments are not sufficiently informative to support such control rules. After a nearly a decade of applying such control rules, a large portion of management units in the International Council for the Exploration of the Sea (ICES) convention and marine fisheries under United States jurisdiction still have uncertain status, because many management units lack a complete suite of fishing mortality and biomass estimates and associated reference points. For those fishery resources with analytical stock assessments and reference point estimates, fishing mortality has generally been reduced to within prescribed limits. The number of stocks in the ICES area with excessive fishing mortality (i.e., greater than the limit reference point) decreased since 1997, but the number of stocks in need of rebuilding increased as a result of excessive fishing or revised reference points. The number of U.S. stocks with excessive fishing decreased and the number of stocks needing rebuilding decreased as a result of stock recovery, revised reference points, or redefined management units. The number of U.S. stocks with uncertain or undefined status substantially decreased. The large portion of stocks with uncertain status in both systems illustrates that such precautionary control rules are applied only to data-rich stock assessments, and are not being applied to management of fishery resources with the most uncertain stock assessments.