Results for Initial Candidate Management Procedure Testing for Greenland Halibut

Rademeyer, R A; Butterworth, Doug S

Results for Initial Candidate Management Procedure Testing for Greenland Halibut

Working Paper

2017-06

Publisher

University of Cape Town

Department

Marine Resource Assessment and Management Group

Faculty

Faculty of Science

Abstract

A number of target-based Candidate Management Procedures (CMPs) are applied to the full set of SCAA-based Operating Models (OMs) and robustness tests for Greenland halibut. These target-based rules are shown to outperform similar slope-based rules, especially in terms of lower inter-annual TAC changes, in achieving the same target of a resource at its MSY level in terms of median exploitable biomass in 20 years (2037). Four CMPs seem to reasonably capture the range from which a final MP might be selected. These have 2018 starting TACs of 15 000 or 20 000t, and are tuned to achieve the target exploitable biomass in 2037 at its MSY level for the baseline OM (OM0) or for Rob15 which assumes future under-reporting of catches at a level similar to the recent past. All four meet the agreed primary depletion probability criterion related to falling below 0.3BMSY. The higher initial TAC choice results in a smaller increase in spawning biomass. Performance is generally robust for the tuning based on the baseline OM0, except for greater depletion under Rob15. If this level of under-reporting is considered a reasonable possibility, a more conservative tuning level (i.e. a higher value of the tuning parameter α) than that for OM0 should be considered when choosing the final MP.

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