A Management Analysis of the Pacific Whiting (Merluccius productus) Fishery Using an Age-Structured Stochastic Recruitment Model

Abstract

An age-structured stochastic recruitment model to the Pacific whiting (M. productus) fishery off the North American pacific continental shelf is applied. A policy algorithm was developed as an aid to management of the fishery which aims to set quotas in such a way as to use strong year-classes in a practical and efficient manner while protecting the stock when it is in a poor condition and environmental conditions do not appear to be conductive to stock improvement in the immediate future. Recruitment in the whiting stock is linked primarily to water temperature in their spawning area. Existing data are used as the basis of a transition matrix for recruitment which depends on both stock level and water surface temperature on the spawning grounds. Comparison with historical data on fishery catch and stock estimates shows model output to be realistic. As a test of the policy algorithm simulation runs with different quota control criteria in the algorithm were compared with 47-yr runs at constant effort and constant quotas. The policy algorithm protected the stock better and provided higher average catch per unit effort (CPUE) than the constant effort and quota cases. In the policy algorithm, average yield can be increased at the expense of CPUE. The choice of quota control criteria depends on management preference for improving yields vs. having less variable effort and higher average CPUE.