Browsing by Author "Coetzee, J"

Now showing 1 - 7 of 7
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    The estimation of uncapped acoustic survey biomass from capped data
    (2007) Cunningham, Carryn L; Butterworth, Doug S; Coetzee, J
    Management of the South African sardine and anchovy resources is critically dependent on estimates of recruitment and spawner biomass obtained from hydroacoustic surveys. These surveys commenced in 1984, but in 1997 new equipment (an EK500 echo sounder) replaced the older EK400 echo sounder. The introduction of the EK500 echo sounder revealed a saturation problem with the EK400 echo sounder, particularly for sardine (Coetzee 2003). Survey estimates since June 1997 were initially ‘capped’ at - 29dB for assessment purposes, to maintain a comparable time-series from 1984.
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    A final record of the generation of data used in the 2011 sardine and anchovy assessments
    (2011) De Moor, Carryn L; Coetzee, J; Durholtz, D; Merkle, D; van der Westhuizen, J J
    The data to which the South African anchovy and sardine assessments are tuned are not raw data. Some of the data have already been subjected to a number of analyses and refinements. These associated calculations are often done “behind the scenes” and their details are seldom recorded. This lack of record can result in a discontinuity in the method used to calculate data for subsequent assessments, particularly if assumptions made in the calculations are not documented and/or a new person becomes responsible for developing the data to be used for input to the assessment. This document serves to record the generation from the raw data of the data used in the anchovy and sardine assessments carried out in 2010 and 2011. All files referred to below are available from the first author.
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    Objectives for the management of the South African pelagic fishery for anchovy and sardine, using OMP-13
    (2012) De Moor, Carryn L; Coetzee, J
    During the MARAM International Stock Assessment Workshop in Cape Town, December 2011, it was recommended that clear broad objectives for the management of the anchovy and sardine fisheries would assist good decision making by all stake-holders (Anon. 2011). This document outlines a suggested list of qualitative objectives for the management of these fisheries under OMP-13 in three tiers. The first tier consists of “nonnegotiable” objectives, which will in due course be defined quantitatively. A second tier consists of core decision objectives, while a third tier consists of further trade-off objectives. The objectives are split between those which address target resource (i.e. sardine or anchovy) concerns, those which address industry concerns and those which address ecosystem concerns. Naturally trade-offs between the objectives in each of these three sets of concerns will exist. At this stage, assigning quantitative definitions to each objective is not attempted.
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    The present agreed hypothesis for South African sardine stock structure
    (2016-11) Butterworth, Doug S; van der Lingen, C D; Coetzee, J; de Moor, Carryn L
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    A record of the generation of data used in the 2011 sardine and anchovy assessments
    (2011) De Moor, Carryn L; van der Westhuizen, J J; Durholtz, D; Coetzee, J
    The data to which the South African anchovy and sardine assessments are tuned are not raw data. Some of the data have already been subjected to a number of analyses and refinements. These associated calculations are often done “behind the scenes” and their details are seldom recorded. This lack of record can result in a discontinuity in the method used to calculate data for subsequent assessments, particularly if assumptions made in the calculations are not documented and/or a new person becomes responsible for developing the data to be used for input to the assessment. This document serves to record the generation from the raw data of the data used in the anchovy and sardine assessments carried out in 2010 and 2011. All files referred to below are available from the first author.
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    A record of the generation of data used in the 2012 sardine and anchovy assessments
    (2012) De Moor, Carryn L; Coetzee, J; Durholtz, D; Merkle, D; van der Westhuizen, J J; Butterworth, Doug S
    The data to which the South African anchovy and sardine assessments are tuned are not raw data. Some of the data have already been subjected to a number of analyses and refinements. These associated calculations are often done “behind the scenes” and their details are seldom recorded. This lack of record can result in a discontinuity in the method used to calculate data for subsequent assessments, particularly if assumptions made in the calculations are not documented and/or a new person becomes responsible for developing the data to be used for input to the assessment. This document serves to record the generation from the raw data of the data used in the anchovy and sardine assessments carried out in 2012. It is an update of de Moor et al. 2011 to include data from November 2010 to October 2011 and new proportions and weights-at-age for anchovy. All files referred to below are available from the first author.
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    A record of the generation of data used in the sardine and anchovy assessments
    (2007) Cunningham, Carryn L; van der Westhuizen, J J; Durholtz, D; Coetzee, J
    The data to which the South African anchovy and sardine assessments are tuned are not raw data. Some of the data have already been subjected to a number of analyses and refinements. These associated calculations are often done “behind the scenes” and their details are seldom recorded. This lack of record can result in a discontinuity in the method used to calculate data for subsequent assessments, particularly if assumptions made in the calculations are not documented and/or a new person becomes responsible for developing the data to be used for input to the assessment. This document serves to record the generation from the raw data of the data to be used in the anchovy and sardine assessments to be carried out in 2007.