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Browsing by Author "De Moor, Carryn L"

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Alternative OMP trade-off curves in response to the request by SAPFIA

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2010 In preparation for OMP-12, SAPFIA requested trade-off curves to be plotted for three cases where changes to the TAC rules and/or constraints of OMP-08 are considered and asked for a trade-off curve to show the effect of alternative choices ... Read more
An alternative relationship to determine future movement of sardine recruits between the "west" and "south" stocks

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2013 de Moor and Butterworth (2013a) explored some possible relationships between the proportion of “west” stock recruits moving to the “south” stock and “west” or “south” stock 1+ biomass or recruitment. A relationship based on the ratio of “south” ... Read more
Application of the ''River Model'' to estimate the impact of fishing on the amount of anchovy available to west coast penguin colonies

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2014 A simple approach is used to estimate the extent to which the amount of anchovy recruits of the year which would otherwise have been available to penguin colonies off the West Coast has been reduced by historic levels of fishing. Results ... Read more
Assessing the South African sardine resource: two stocks rather than one?

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2015 Sardine Sardinops sagax distributed off the west and south coasts of South Africa have traditionally been assumed to comprise a single well-mixed stock for assessment and management purposes. New research, however, lends weight to the possibility ... Read more
Assessment of the South African anchovy resource using data from 1984 – 2009: attempts to resolve residual trends

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2010 Further testing of the proposed baseline anchovy assessment, “A0” from de Moor and Butterworth (2010) is undertaken. It is proposed that the assumption of two stock recruitment “regimes” (pre- and post-2000) be taken forward as a robustness test ... Read more
Assessment of the South African anchovy resource using data from 1984 – 2010: posterior distributions for the two base case hypotheses

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2011 The operating model (OM) for the South African anchovy resource has been updated from that used to develop OMP-08 given four more years of data and a revised time series of commercial catch. The OM with results at the posterior mode has already ... Read more
Assessment of the South African anchovy resource using data from 1984 – 2010: results at the posterior mode

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2011 The operating model (OM) for the South African anchovy resource has been updated from that used to develop OMP-08 given four more years of data and a revised time series of commercial catch. A Hockey Stick stock recruitment relationship, and ... Read more
Assessment of the South African anchovy resource using data from 1984 – 2010: variability in natural mortality

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2011 Initial results of the updated assessment of the South African anchovy resource, using data from 1984 to 2010, were presented by de Moor and Butterworth (2011). This work included the use of a random effects model for adult natural mortality ... Read more
Assessment of the South African anchovy resource using data from 1984-2009

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2010 The assessment of the South African anchovy resource has been updated given three more years of data and a revised time series of commercial catch. The base case hypothesis has the same juvenile and adult natural mortality rates as previous ... Read more
Assessment of the South African sardine resource using data from 1984-2010: further work towards a base case single stock hypothesis

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2011 Further work towards choosing a base case single sardine stock hypothesis operating model has been undertaken. This work extends that reported in de Moor and Butterworth (2011). Read more
Assessment of the South African sardine resource using data from 1984-2010: further work towards a base case single stock hypothesis

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2011 The sardine assessment is extended to consider three hypotheses for the presence of two (west and east) stocks separated at Cape Agulhas. The first hypothesis of two completely separated stocks is dismissed, as it implies that an unrealistically ... Read more
Assessment of the South African sardine resource using data from 1984-2010: initial results for a two stock hypothesis

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2011 The sardine assessment is extended to consider three hypotheses for the presence of two (west and east) stocks separated at Cape Agulhas. The first hypothesis of two completely separated stocks is dismissed, as it implies that an unrealistically ... Read more
Assessment of the South African sardine resource using data from 1984-2011, with some results for a single stock hypothesis

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2012 Although the base case operating model for the South African sardine resource was updated from the last assessment (Cunningham and Butterworth 2007) to take account of new data collected between 2007 and 2010 (de Moor and Butterworth 2011a), ... Read more
Assessment of the South African sardine resource using data from 1984-2011: further results for a two stock hypothesis

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2013 As part of the process of updating the assessment of the South African sardine resource, a model of the sardine two mixing-stock hypothesis is being developed. This hypothesis postulates a “west” stock distributed west of Cape Agulhas and a ... Read more
Assessment of the South African sardine resource using data from 1984-2011: initial results for a two stock hypothesis

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2012 As part of the process of updating the assessment of the South African sardine resource, a sardine two mixing-stock hypothesis is to be tested. This hypothesis postulates a “west” stock distributed west of Cape Agulhas and a “south” stock ... Read more
Assessment of the South African sardine resource using data from 1984-2011: results for a two stock hypothesis at the posterior mode

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2013 As part of the process of updating the assessment of the South African sardine resource, a model of a sardine two mixing-stock hypothesis has been developed. This hypothesis postulates a “west” stock distributed west of Cape Agulhas and a ... Read more
Can anchovy age structure be estimated from length distribution data collected during surveys?

Author: De Moor, Carryn L ; Butterworth, Doug S ; Coetzee, J C Date: 2013 Historically, a time-series of proportions-at-age 1 from annual November hydro-acoustic surveys has been used to inform the assessment of, and in particular the choice of appropriate values for juvenile and adult natural mortality for, the ... Read more
Catch to natural predation ratios for sardine and anchovy

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2010 One approach to place the size of annual fishery catches of sardine and anchovy into perspective is to contrast them with annual losses to natural mortality, which correspond to the amounts consumed by natural predators. This is pursued ... Read more
Comparison of sardine November proportion-at-age from different length frequencies and age readers

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2011 de Moor and Butterworth (2009) recommended that a new method to weight the trawls when calculating the sardine length frequency observed during the November surveys be applied. This new method involved weighting the individual trawls equally ... Read more
Did high directed sardine TACs cause the rapid decline in sardine abundance

Author: De Moor, Carryn L ; Butterworth, Doug S Date: 2009 A question that has been raised is whether the rapid decline in the sardine abundance after 2002 can be attributed either in part or in full to the relatively large sardine catches in the early part of this decade. One way to consider this ... Read more

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