Browsing by Author "Rademeyer, R A"

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    CMP projections under XSA in comparison to the SCAA baseline (OM0)
    (2017-06) Rademeyer, R A; Butterworth, Doug S
    As an illustrative exercise, the CMP testing framework is applied to an Operating Model provided by an XSA assessment to show how this may be done. Results are reported for the CMP1 candidate management procedure, and performance statistics indicate reasonable robustness compared to those for the SCAA OM0. The results given should, however, not be over-interpreted as the XSA assessment used is not necessarily agreed and accepted at this time.
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    Examples of Management Procedure Outputs for Greenland Halibut
    (2017-04) Rademeyer, R A; Butterworth, Doug S
    The results of some variants of a simple target-based Management Procedure (MP) are provided purely as examples to illustrate the performance trade-offs and robustness considerations involved in selecting an MP, and also to illustrate the various performance statistics put forward at the April Scientific Council meeting in Vigo.
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    Management Procedures for Greenland Halibut
    (2017-03) Rademeyer, R A; Butterworth, Doug S
    This document expands upon the baseline and sensitivity SCAA assessments of the Greenland halibut resource by Rademeyer and Butterworth (2017). First, projections under different levels of a constant catch are reported. These suggest that for all the cases of assessments (operating models – OMs) considered, an annual TAC of 20000t would be sustainable, but for most of these cases 30000t would not. Some variants of a simple target-based Management Procedure (MP) are applied purely as examples to illustrate the performance trade-offs and robustness considerations involved in selecting an MP.
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    Results for Initial Candidate Management Procedure Testing for Greenland Halibut
    (2017-06) Rademeyer, R A; Butterworth, Doug S
    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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    Specifications of the South African Hake 2016 Reference Case Assessment
    (2017-02) Rademeyer, R A; Butterworth, Doug S
    This paper gives full algebraic specifications of the 2016 South African hake Reference Case assessment. The data used as input to the Reference Case are listed in Appendix A. Parameter estimates and detailed values for different contributions to the negative log-likelihood are also included. The Reference Case results are given in Appendix B. The results of the Reference Case differ slightly from those presented in Rademeyer and Butterworth (2016) because a small error has been corrected in the survey catch-at-length data computations.
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    Update of the proposed model framework to form the basis for immediate future assessments of the South African hake resource. BENEFIT/NRF/BCMLE December 2004 Stock Assessment Workshop document
    (MARAM, 2004) Rademeyer, R A; Butterworth, D S
    Update of the proposed model framework to form the basis for immediate future assessments of the South African hake resource. BENEFIT/NRF/BCMLE December 2004 Stock Assessment Workshop document