Evaluation of threshold management strategies for groundfish off the U.S. West Coast

Abstract

Monte Carlo simulations and equilibrium analyses are used to explore the behavior of threshold management strategies. The analyses explore the medium- to long-term implications of uncertainty about the steepness of the stock–recruitment relationship, variation as well as possible temporal autocorrelation in recruitment, and estimation and implementation uncertainty. The results highlight the trade-offs among various management strategies, in particular the trade-offs between average catch, inter-annual variation in catch, and the risk of dropping below the Pacific Fishery Management Council (PFMC) overfished threshold of 25% of the average unfished spawning biomass. Uncertainty regarding steepness is the major source of variation in the final size of the resource and whether it is below the overfished threshold, although the extent of recruitment variability also impacts these quantities. The extent of inter-annual variation in catches is determined primarily by the amount of implementation error. Although the values for the various performance measures depend on all of the factors examined to some extent, the impact of interactions among these factors is generally small.