Research Document - 2011/063

Management procedures for the multi-gear sablefish (Anoplopoma fimbria) fishery in British Columbia, Canada

By S.P. Cox, A.R. Kronlund, and L. Lacko

Abstract

This paper describes a management strategy evaluation process for the multi-gear sablefish (Anoplopoma fimbria) fishery in British Columbia, Canada. Fishery objectives and reference points are based on Canada's Sustainable Fisheries Framework (SFF; DFO 2009b) and consultation with fishery stakeholders. Management procedures are developed to address topics of concern to both industry stakeholders and managers, including: (i) potential risks associated with discontinuing the sablefish standardized survey; (ii) evaluating management options to reduce the conservation and economic impacts of at-sea release and release mortality of sub-legal sablefish; and (iii) identifying a new management procedure for providing the best catch and catch stability performance. Part of this new management procedure involves "tuning" priors on stock assessment model parameters to improve catch performance. The operating model used to test management procedure robustness was developed to represent alternative hypotheses about sablefish natural mortality, at-sea release mortality rates, individual growth rate, and recruitment autocorrelation The model is structured by age and also by growth-group, where the latter dimension is added as part of our evaluation of size-based at-sea release processes and potential regulatory changes aimed at reducing these activities. Our results suggest that full retention or avoidance of sub-legal sablefish would provide the best overall catch, catch stability, and conservation performance although the gains are small relative to current management. Because these options would require a regulation change they are not feasible in the short-term. The next best procedure uses only the stratified random sablefish survey, a stock assessment model with very informative priors, and a harvest control rule that is less conservative than the DFO's SFF default rule.  Consistent application of these procedures results in sablefish biomass growth to levels near or above BMSY and an extremely low probability of decline ( <5% ) to levels below 0.4BMSY as required under the SFF.  Projected catch levels in the short-term were very sensitive to stock assessment model tuning and the harvest control rule.  Under the apparent "best" rule, median catch levels increase steadily to levels near, or just below MSY, and inter-annual variation remains below approximately 8%.

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