Research Document - 2009/042

Evaluation of interim harvest strategies for sablefish (Anoplopoma fimbria) in British Columbia, Canada for 2008/09

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

Abstract

This paper applies a management strategy evaluation (MSE) approach toward identifying an interim management procedure for setting sablefish (Anoplopoma fimbria) quotas in 2008/2009 and beyond. We employ the MSE methodology developed by Cox et al. (2008) to evaluate the likely performance of data-based and model-based management procedures under four simulation scenarios for sablefish stock dynamics. Conservation, catch variability, and catch performance are compared to four management objectives that were developed through consultations with industry stakeholders and managers. Our simulations indicate that 70-80% of the management procedures examined would likely fail to meet specified conservation objectives under some scenarios for sablefish population dynamics. These failures occurred despite the fact that most procedures rebuild the sablefish stock over 40 years. The remaining "admissible" management procedures show the capability to improve stock status within 3-7 years with 90% certainty even under the most pessimistic scenario for stock productivity and current status. TAC levels for 2008 under these admissible procedures range from 1,500 to 2,700 tonnes; however, most will decrease TACs by up to 50% between 2009 and 2014 if the current stock decline continues. The simulated time required to maintain the spawning stock above 2007 levels with 90% certainty ranged from 4 to 7 years when the 2008 TACs were combined with the highest performing data-based management procedure. Advice in this paper is subject to several limitations based on our current representation of sablefish population dynamics in the operating model scenarios. High discard rates in all fisheries are of greatest concern at the moment because (i) our operating model estimates of stock status would be optimistic and (ii) failing to account for discard mortality in future projections means that actual recovery rates will be slower.

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