Working Papers

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http://hdl.handle.net/11427/29131

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Browsing Working Papers by Publication Type "Report"

Now showing 1 - 7 of 7
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    2018 updated south coast rock lobster assessment results
    (2018) Johnston, Susan; Butterworth, Doug S
    The 2017 assessment of the resource is updated given two further years of catch-at-length data now available. Recruitment is estimated to have increased over the last two seasons compared to the previous three seasons when recruitment was estimated to be poor. The spawning biomass trajectory decreases slightly over recent years. Current spawning biomass is estimated to be 27% of K. The RC MSY estimate is 259 MT at a Bsp/K of 0.27. Fmsy is estimated to be 0.112. The RC model thus estimates that the resource is currently slightly above Bmsy.
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    Restricted
    Final results for the abalone spatial- and age-structured assessment model for Zones A, B, C and D in 2013
    (MARAM, University of Cape Town, 2013) Brandão, Anabela; Butterworth, Doug S
    The 2012 assessment of abalone in Zones A-D is updated to include new data and modified to take the standard error of the estimated poaching trend into account. Projections are shown for different scenarios for the future commercial and poaching catches in Zone A and Zone B. Current poaching levels (average of 2012 and 2013), if continued, would not be sustainable.
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    Open Access
    Mapping provision in HE: the present and the possible
    (2022-03-15) Czerniewicz, Laura
    This paper is about Higher Education (HE) teaching provision in terms of a) its language and key concepts b) the types, modes and means presently in existence in South Africa and emergent globally and c) the implications for policies and regulatory frameworks.
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    Open Access
    Projections under the selected Management Procedure for Greenland Halibut
    (2018) Rademeyer, Rebecca; Butterworth, Doug S
    Figures 1 to 5 plot the projected 95, 90 and 80% probability envelopes as well as the projected medians under the revised Management Procedure adopted in 2017 for Greenland Halibut for a series of quantities (annual catch, recruitment, and the five survey indices of abundance together with the composite index which combines the five) for the following SCAA-based Operating Models: - OM1 (the Baseline, using data including 2016 and the O3 set of surveys), - OM2 (larger recruitment variability with R=0.6), - OM4 (loRec – the recruitment of the first 8 years of the projections are at 50% of the level predicted by the stock-recruit function), - OM7 (110TAC – future catches are taken as 110% of the TAC) and - OM8 (noplus – zero selectivity for the plus group). The probability envelopes have been computed from a 9-point averaging approach (see Appendix below) from 500 replicates. The 9-point approach was selected as it offered a reasonable trade-off between preserving trend and eliminating “jaggedness” from Monte Carlo variation.
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    Open Access
    Results for the abalone spatial- and age-structured assessment model for Zones A, B, C and D in 2011
    (MARAM, University of Cape Town, 2011) Brandão, Anabela; Butterworth, Doug S
    The 2009 assessment of abalone in Zones A-D is updated to take new data and a more reliable basis for estimation of poaching trends over the last four years into account. Sensitivity to a number of model assumptions and data input variations is checked, and generally appears to be slight. Viewed overall, the results do not suggest any major revisions to perceptions of resource status and future trends under current poaching levels to those from the 2009 assessment.
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    Open Access
    Results for the abalone spatial- and age-structured assessment model for Zones A, B, C and D in 2012
    (MARAM, University of Cape Town, 2012) Brandão, Anabela; Butterworth, Doug S
    The 2011 assessment of abalone in Zones A-D is updated to take new data into account. Projections are shown for different scenarios for the future commercial and poaching catches in Zone A and Zone B. Current poaching levels (average of 2011 and 2012) if continued, would not be sustainable.
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    Open Access
    Trends in policing effort and the number of confiscations for West Coast rock lobster
    (MARAM, University of Cape Town, 2011) Brandão, Anabela; Johnston, S; Butterworth, Doug S
    To obtain overall annual rates of increase in number of confiscations and in policing effort in a manner that takes into account possible monthly effects and in the case of policing effort, the fact that various types of policing exercises are carried out, Generalized Linear Models (GLMs) are applied to these data, as summarised in Table 1.