Browsing by Author "Edwards, Charles"

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    Participatory stock assessment of abalone in Zones E and G
    (MARAM, University of Cape Town, 2007) Edwards, Charles; Hauck, Maria; Plag´anyi, Eva
    The stock assessment for abalone is significantly hampered by insufficient information on the levels of poaching in each management zone. To assist with our understanding of resource dynamics, stakeholder interviews were conducted to obtain information on the levels of poaching taking place and trends in magnitude over time. This participatory approach represented a pilot study into the use of interview data to inform modeling of the resource. As such, effort was concentrated on Zones E and G. These are two of the least productive Zones with consequently fewer divers operating. The investigation was split into two. The first part was to assess and understand the types of information available for potential inclusion in the modeling process [1]. The second part was actual execution of the participatory stock assessment using the information collected. This report details the outcome from Part 2.
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    Preliminary GLM standardisation of the commercial CPUE series for abalone in Zones E and G from 1980 to 2007
    (2007) Edwards, Charles; Plagányi, Éva E; Butterworth, Doug S
    The commercial CPUE series is considered during modeling of resource dynamics as an index of population abundance. However, a number of factors other than abundance may influence recorded values. Where sufficient data exists, General Linear Model (GLM) standardisation is able to take into account some of these effects, thereby producing a more reliable index.
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    Preliminary Schaefer model predictions of abalone dynamics in Zones E and G based on commercial CPUE data from 1980 to 2007
    (2007) Edwards, Charles; Plag´anyi, Eva
    Here we present the revised predictions of abalone dynamics in Zones E and G. As in the previous assessment [1], predictions are based on a discrete Schaefer model [7] of biomass dynamics. In this implementation however, parameter estimates are obtained using Bayesian methods.
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    Report from stakeholder interviews concerning abalone poaching in Zones E and G
    (2007) Edwards, Charles; Hauck, Maria
    The stock assessment for abalone is significantly hampered by insufficient information on the levels of poaching in each management zone. To assist with our understanding of resource dynamics, stakeholder interviews were conducted to obtain information on the levels of poaching taking place and trends in magnitude over time. This participatory approach represented a pilot study into the use of interview data to inform modeling of the resource. As such, effort was concentrated on Zones E and G. These are two of the least productive Zones with consequently fewer divers operating. The investigation was split into two. The first part was to assess and understand the types of information available for potential inclusion in the modeling process. The second part was actual execution of the participatory stock assessment using the information collected. This report details the outcome from Part 1.
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    Open Access
    Schaefer model predictions of abalone dynamics in Zones E and G based on commercial CPUE data from 1980 to 2007
    (University of Cape Town, 2007) Edwards, Charles; Plagányi, Eva
    Here we present the revised predictions of abalone dynamics in Zones E and G. As in the previous assessment [1], predictions were based on a discrete Schaefer model [12] of biomass dynamics. In this implementation however, parameter estimates were obtained using Bayesian methods.
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    Open Access
    Standardisation of the commercial CPUE series for abalone in Zones E and G from 1980 to 2007 using a mixed effects model
    (2007) Edwards, Charles; Plagányi, Éva E; Brandão, Anabela; Butterworth, Doug S
    The commercial CPUE series is considered during modeling of resource dynamics as an index of population abundance. However, a number of factors other than abundance may influence recorded values. Standardisation is able to take into account some of these effects, thereby producing a more reliable index.