Browsing by Author "Andrea, Ross-Gillespie"

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    Bridge-building between the 2017 and 2018 hake RC assessment models
    (2018) Andrea, Ross-Gillespie; Butterworth, Doug S; Deon, Durholtz; Mike, Bergh
    This document builds on FISHERIES/2018/MAY/SWG-DEM/20, which summarised changes made to the hake Reference Case (RC) assessment model over the period from May 2017 to May 2018. Following the tabling of DEM/20, one further update has been made to the RC model, namely that CPUE and catch data based on species splitting algorithm Model A6b (instead of Model A6) are now being used for the RC. However, rather than re-run all the bridge-building models, the results from DEM/20 have been retained and thus compare the various “snapshots” with the RC model at that time (i.e. May 2018). Results for the most recent (July 2018) RC model using the model A6b data have been included in the tables, but not the figures, in the interests of time, given that what is more important here is to indicate impacts in relative (not necessarily absolute) terms. Note further that during the course of the workshop it became apparent that the information provided in Appendix A was not complete; hence this document has been revised to address this, with further information provided in Appendix A, and an Appendix C is now added with information from one of the workshop working papers.
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    Projection results for OMP2018, as well as other CMPs tested
    (2018) Andrea, Ross-Gillespie; Butterworth, Doug S
    Performance statistics are contrasted for seven hake CMPs: three options for the b control parameters crossed with two options for the cap on the TAC, and further a no cap option for the b+5% option. Despite a higher average catch, the no cap option seems undesirable because of poor lower 5%ile depletion and high AAV values. Instances of low 5%ile depletion values for M. capensis are shown to be linked to three likely less plausible OMs amongst the nine OMs that make up the Reference Set. However, in those cases, with the 2017 starting M. capensis spawning biomasses below BMSY, the CMPs would seem to secure a recovery towards BMSY. Based on these results, the DAFF DWG decided to propose the b+5% option with a cap of 160 000t on the annual TAC.
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    Specification and Conditioning of the Hake OMP2018 Reference Set models
    (2018) Andrea, Ross-Gillespie; Butterworth, Doug S
    "Specification and Conditioning of the Hake OMP2018 Reference Set models" is work that has been presented at MARAM International Workshop (IWS) 2018.