Browsing by Subject "squid"

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    A conversion of squid effort from hours to man-days and some related considerations
    (2006) Glazer, Jean Patricia; Butterworth, Doug S
    The South African jig squid fishery is a constant effort fishery, with the current unit of effort being one of man-hours. The target effort level is 3030 thousand man-hours based on recent assessment results, and the mechanism of effort control is to limit the number vessels (and crew) active in the fishery. The long term rights allocation process resulted in 109 companies with a complement of 123 vessels (and 2233 crew) being granted rights in this fishery. 214 crew and 16 vessels have been set aside for appeals. It is of concern that the target effort level has been exceeded in recent years (Figure 1), which suggests that the current restrictions on effort are not adequate. Measures that might be invoked to reduce effort include, for example, capping the days spent at sea, lengthening the closed season, introducing an additional closed season or combinations of these.
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    A re-analysis of the squid jig CPUE data
    (2006) Glazer, Jean Patricia; Butterworth, Doug S
    The catch per unit effort (CPUE) indices from the squid jig fishery have to date been expressed in terms of catch per man-hour (Roel, 1998). Industry has for many years questioned the use of man-hours as the unit of effort since it is alleged that the information contained in the database regarding the number of hours fished is unreliable. A re-analysis of the jig catch and effort data has therefore been undertaken, with the unit of effort revised to one of man-days, under the assumption (though see further discussion below) that the proportion of a day spent fishing has remained roughly unchanged over time.
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    Updated squid assessment results
    (2013) Glazer, Jean Patricia; Butterworth, Doug S
    Glazer & Butterworth (2013) reports progress on refinements to the squid stock assessment model focusing particularly on replacing the discrete Pope catch equations with differentiable Baranov catch equations as recommended by the Panel of the International Stock Assessment Workshop held at UCT in December 2012. A comparison of key parameter estimates as per the Pope and Baranov models (utilizing data to 2011) indicated that although initial recruitment, and hence biomass, is estimated to be somewhat higher for the Baranov model (driven mainly by the lower estimate of h in that model), the ratio of current stock status relative to pristine (��2012 ∗ ��1971 ∗ ) was at a similar level for both models. This paper reports further results to those in Glazer & Butterworth (2013): • A comparison of risk statistics for the Pope and Baranov models where each model was projected 5000 times into the future from their joint posterior mode values • Updated joint posterior mode parameter estimates for the Baranov model including data to 2012