Browsing by Subject "South African hake resource"

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    Candidate management procedures for the South African hake resource: Draft objectives and testing methodology
    (2010) Rademeyer, Rebecca A; Butterworth, Doug S
    Though revised operational objectives should only be finalised through an iterative process as the results of simulation tests of Candidate Management Procedures (CMPs), and hence their trade-off implications, become available, this process merits initiation at the present time.
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    Conditioning of the full set of robustness tests for the South African hake resource to be used in OMP-2010 testing and constant catch projections
    (2010) Rademeyer, Rebecca A; Butterworth, Doug S
    Results for conditioning of the full set of robustness/sensitivity tests for the current hake OMP revision process are given, and projections carried out under a constant catch strategy. Although the final one or two CMPs will be checked on the complete suite of robustness tests, only a selected subset of robustness tests will be used to test the CMPs routinely. The intention is therefore to reduce the number of robustness tests that will be run routinely on the CMPs by selecting the ones which appear under constant catch projections to present the greatest challenges from a resource conservation perspective. (Naturally constant catch projections do not provide discrimination amongst tests that involve changes to default assumptions for aspects of future data such as changes in precision, so that such tests will remain retained in this selected set.) A projected constant catch of 150 000t has been chosen as this will be more informative (in terms of the poor resource conservation performers) than a constant catch set at the current TAC.
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    The effect of a cap on the TAC and restricting the 3-yr maximum decline in the TAC in candidate management procedure testing for the South African hake resource
    (2010) Rademeyer, Rebecca A; Butterworth, Doug S
    Two possible variants suggested at the last DWG meeting to the Base Case hake CMP structure are examined. The results obtained suggest no need to modify this baseline structure.
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    Further candidate management procedures projections for the South African hake resource
    (2014) Rademeyer, Rebecca A; Butterworth, Doug S
    This document reports further developments in the hake OMP revision process. First the requested 150 000t upper cap is placed on the TAC, and tunings to different average TACs over the next 10 years are contrasted, together with options for a prefixed TAC for the next two years. The option of a soft lower cap on the TAC of 125 000t is explored, linked to a metarule for overriding this if the overall abundance index for M. paradoxus falls below a specified threshold. While it seems more likely than not that the introduction of this soft lower cap would make for a more stable fishery, there remains an appreciable chance that it may necessitate larger TAC reductions, and to lower TAC levels, than would otherwise be the case. Options to reduce the “lag” effects between changes in resource trends and in the TAC are explored, but with little success; basing the control rule on abundance index averages over the last two rather than last three years leads to greater interannual TAC variability. Results for an initial exploration of robustness to decreases in carrying capacity (a possible effect of climate change) point to the importance of further development of metarules to override the constraint on the 5% maximum downward TAC adjustment.
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    Routine update of the 2008 baseline assessment for the South African hake resource
    (2009) Rademeyer, Rebecca A; Butterworth, Doug S
    The 2008 “New Baseline” assessment for hake is updated to take account of further information that has become available over the past year. The update leads to only slight changes to results, which continue to manifest a lack of fit to catch-at-length distributions. The “New Reference Case” methodology (Rademeyer and Butterworth, 2009) , which resolves that discrepancy, suggests a less depleted M. paradoxus but a more depleted M. capensis resource than does this updated “New Baseline” assessment.
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    Yet further CMP projections for the South African hake resource
    (2014) Rademeyer, Rebecca A; Butterworth, Doug S
    This document addresses issues raised at and outstanding from the previous discussions of the hake OMP revision at the DWG meeting on 26 August, and concludes by listing issues still requiring choices/analyses to be able to finalise this OMP revision process at the next DWG meeting on 13 October.