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Browsing by Author "Butterworth, Doug"

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2020 sole dynamic Schaefer production model results

Author: Glazer, Jean ; Butterworth, Doug Date: 2020 The sole resource is modelled by a dynamic Schaefer production model which allows for a drop in the value of the intrinsic growth rate parameter from 2000 onwards. The model is fit to the available CPUE and survey abundance indices. These ... Read more
Age-Structured Production Model (ASPM) assessments of the Alfonsino (Beryx splendens) resource in the SIOFA area of the Southern Indian Ocean

Author: Brandão, Anabela ; Butterworth, Doug ; Johnston, Susan Date: 2020 An Age-Structured Production Model is applied to assess the Alfonsino (Beryx splendens) resource in the West and East SIOFA areas of the Southern Indian Ocean. Data limitations restrict these applications to deterministic variants, which ... Read more
Calculating an informative prior distribution for the bias of hydro‐acoustic survey estimates of the biomass of the South African anchovy

Author: de Moor, Carryn ; Coetzee, Janet ; Butterworth, Doug Date: 2020 A prior distribution for the bias of the hydro‐acoustic survey estimates of the biomass of the South African anchovy is developed by considering the bias associated with the individual sources of error. Read more
Can the wide range of resource behaviours evident across the ABFT MSE interim grid of OMS be “tamed” by the feedback control provided by a CMP?

Author: Butterworth, Doug ; Rademeyer, Rebecca Date: 2020 The interim grid of OMs is used to explore the 30-year projection behaviour for catches and the status of the eastern and western ABFT stocks (expressed in terms of their abundance relative to dynamic Bmsy by the Br30 statistic) for both ... Read more
Initial results from the development of a new OMP 2020 for Tristan da Cunha island rock lobster resource

Author: Johnston, Susan ; Butterworth, Doug Date: 2020 Development of a revised OMP (OMP 2020) for the Tristan island rock lobster resource first leads to a recommendation to include the annual Edinburgh/GS CPUE and the biomass survey index as well as the Tristan powerboat CPUE index as inputs ... Read more
OMP 2020 candidates for the Nightingale rock lobster fishery

Author: Johnston, Susan ; Butterworth, Doug Date: 2020 The performances of a number of OMP candidates for the fishery for rock lobster at Nightingale are reported. These performances do not show much variation amongst the various candidates. For this and other reasons it is recommended that CMP9 ... Read more
Re-analysis of the island closure experiment results to implement the suggestions of the December 2020 International Panel

Author: Ross-Gillespie, Andrea ; Butterworth, Doug Date: 2021 The suggestions of the December 2020 International Panel for further analysis of the results from the island closure experiment, in particular to use the same data within a common framework to facilitate comparisons, and to include month as ... Read more
Results of the progression towards a proposed Management Procedure for the Toothfish (Dissostichus eleginoides) Resource in the Prince Edward Islands vicinity

Author: Brandão, Anabela ; Butterworth, Doug Date: 2020 Brandão and Butterworth (2019a) investigated various target-based Candidate Management Procedures (CMPs) for the Prince Edward Islands toothfish resource; however, their performances under some operating models were not satisfactory so that ... Read more
A summary of results for the island closure experiment

Author: Butterworth, Doug ; Ross-Gillespie, Andrea Date: 2021 A simple summary is offered of the results of the island closure experiment reported in Ross-Gillespie and Butterworth (2021), which implemented the suggestions of the December 2020 International Panel. A single result in selected for each ... Read more
Updated extension of a photo-identification based assessment model to southern right whales in South African waters to allow for the possibility of an early abortion of the calf in the model

Author: Brandao, Anabela ; Ross-Gillespie, Andrea ; Vermeulen, Els ; Butterworth, Doug Date: 2021 This paper updates analyses (Brandão et al., 2020) of an extension of the model developed by Brandão et al. (2019) so as to now include sightings data for 2019 and 2020. Brandão et al. (2020) had been modified to include the possibility of ... Read more