Browsing by Author "Brandão, A"

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    A proposed management procedure for the toothfish (Dissostichus eleginoides) resource in the Prince Edward Islands vicinity
    (2009) Brandão, A; Butterworth, D S
    The status of the toothfish resource in the Prince Edward Islands region is unclear because CPUE data suggest considerable depletion, whereas catch-at-length information indicates that past catches have had relatively little impact on abundance. A Management Procedure (MP) approach is proposed to provide a sound scientific basis to recommend future TACs in the face of this appreciable uncertainty. Four Operating Models (OMs) reflecting ‘Optimistic’, ‘Intermediate’, ‘Less Pessimistic’ and a ‘Pessimistic’ current status for the resource are developed which take account of the different selectivities of past longline and pot fisheries. These OMs are used for trials of a candidate generic MP which could provide future TAC recommendations for this resource. The MP uses two data sources: the recent trend in longline CPUE and the mean length of the catches made. An MP with control parameter values specified is proposed for implementation based on the results of the trials. Given the importance of an adequate catch rate for the economic viability of the fishery, the choice of control parameter values focused primarily on a reasonable probability of securing a catch rate increase, whatever the current resource status. MP performance is reasonably robust across a range of sensitivity tests, although it does deteriorate in conservation terms if the stock-recruitment curve steepness h is low. These tests also indicate that monitoring of future catch-at-length information would be necessary to guard against a change in selectivity towards greater catches of older fish.
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    Updated 2017 GLMM-standardised lobster CPUE from the Tristan da Cunha outer group of islands
    (2017-05) Johnston, S J; Brandão, A; Butterworth, Doug S
    The longline CPUE series for Inaccessible and Gough islands are GLMM standardised through to 20161. For Nightingale, the fishery was closed for the 2011 season and catches were set at precautionary levels for the 2011 and 2012 seasons. The Nightingale GLMM model thus excludes 2011 and 2012, although it now includes 2013-2016 for this island. Year, month, area, trap-type, soak time, depth and year-area interactions are treated as fixed effects, and year-month interactions treated as a random effect. The standardised CPUEs for Inaccessible and Nightingale continue to be optimistic, and both show increases since the previous season. For Gough, the standardised CPUE value for the current season is lower than that of the previous season, but still well above the OMP target level Itar.