Browsing by Subject "Toothfish"

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    2006 assessment of the toothfish (Dissostichus eleginoides) resource in the Prince Edward Islands vicinity
    (2006) Brandão, Anabela; Butterworth, Doug S
    The ASPM assessment of the Prince Edward Islands toothfish resource by Brandão and Butterworth (2005) that permitted annual fluctuations about a deterministic stockrecruitment relationship is updated to take account of further catch, GLM standardised CPUE and catch-at-length information that has become available for the years 2005 and 2006. The assessment allows for a second fleet to accommodate data from a pot fishery that operated in 2004 and 2005. Updated biological parameter values for Subarea 48.3 are incorporated and lead to less optimistic results. The resource is estimated to be at about 40% of its average pre-exploitation level in terms of spawning biomass. It is suggested that it would be prudent to restrict annual legal catches to 500 tonnes or less, unless a large proportion of the catch is to be taken by pots (which avoid the cetacean predation associated with longlining). Specific issues raised at WGFSA-SAM 2006 about this assessment are addressed.
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    Obtaining a standardised CPUE series for toothfish (Dissostichus eleginoides) in the Prince Edward Islands EEZ calibrated to incorporate both longline and trotline data over the period 1997-2012
    (2012) Brandão, Anabela; Butterworth, Doug S
    The previous GLMM standardisation approach for PEI toothfish (Spanish) longline CPUE data is extended to include data for the 2011-2012 seasons and the same approach is applied to trotline CPUE data for the 2008–2012 period. CPUE data from a research program carried out in 2012 in which longline and trotline sets were paired to within three nautical miles and a period of two weeks is analysed to obtain a calibration factor for longlines and trotlines. A model is then fitted to combine the two individual standardised CPUE series and the calibration factor to obtain a “calibrated” longline CPUE series (incorporating both longline and trotline information) and an estimate of the calibration factor. This indicates a drop of about 44% in standardised CPUE in 2012 compared to the immediately preceding years; however it must be noted that the data in 2012 is available only until August.
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    Obtaining a standardised CPUE series for toothfish (Dissostichus eleginoides) in the Prince Edward islands EEZ calibrated to incorporate both longline and trotline data over the period 1997-2013
    (2013) Brandão, Anabela; Butterworth, Doug S
    The previous GLMM standardisation approach for PEI toothfish (Spanish) longline CPUE data is extended to include data for the 2012 and 2013 seasons and the same approach is applied to trotline CPUE data for the 2008–2013 period. CPUE data from a research program carried out in 2012 and 2013 in which longline and trotline sets were paired to within three nautical miles and a period of two weeks is analysed to obtain a calibration factor between longlines and trotlines. A model is then fitted to combine the two individual standardised CPUE series and the calibration factor to obtain a “calibrated” longline CPUE series (incorporating both longline and trotline information) and an estimate of the calibration factor. This indicates an increase of about 18% in standardised CPUE in 2013 compared to the preceding year, but this remains about 20% below the 2011 value. However it should be noted that data for 2013 are available only until July.
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    An update on the development of a management procedure for the toothfish (Dissostichus eleginoides) resource in the Prince Edward Islands vicinity
    (2006) Brandão, Anabela; Butterworth, Doug S
    Two Operating Models (OMs) reflecting an “Optimistic” and a “Pessimistic” current status for the toothfish resource in the Prince Edward Islands region that were developed last year are updated given further data. These models are for use for initial trials of candidate Management Procedures (MPs) which could provide future TAC recommendations for this resource. Deterministic projections under a constant future catch suggest that the two scenarios will only be qualitatively distinguished in the shortterm by an increase in the mean length of longline-caught toothfish over the next five years for the “Pessimistic”, but not the “Optimistic” case. Accordingly the performance of a simple MP control rule based upon recent trends in both CPUE and this mean length is investigated. This MP is able to secure a faster increase in the TAC for the “Optimistic” case, and some recovery in abundance for the “Pessimistic” scenario, but neither is as appreciable as one might wish. Suggestions for future work are made.