FISHERIES_2016_OCT_SWG-DEM_69 Toothfish assessment_update_amended.pdf (830.01 kB)
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Updated assessment of the toothfish (Dissostichus eleginoides) resource in the Prince Edward Islands vicinity to include data from 1997 to 2016

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posted on 22.07.2022, 09:12 authored by Anabela BrandaoAnabela Brandao, Doug ButterworthDoug Butterworth

The assessment of the Prince Edward Islands (PEI) toothfish (Dissostichus eleginoides) resource carried out by Brandão and Butterworth (2015a) is updated to take further data available for 2015 and 2016 (up to May) into account. 

This update again also incorporates (now updated) tag-recapture data and a new basis to estimate the extent of cetacean depredation. For the Base case and many of the assessment sensitivities the resource is estimated to be at a depletion (in relation to its average pre-exploitation level in terms of spawning biomass) in the 51-58% range (slightly better than before the new data were added, though the resource remains estimated to be decreasing in abundance). 

Introduction of the tag recapture data hardly changes point estimates but does reduce estimation variance. Projections suggest that the resource would increase slowly under constant annual future catches of 500 t. This would remain the case for somewhat higher catches as well, but it remains a concern that for the last three years (2011-2013) of the longline CPUE is well below model predictions. The trotline CPUE does however show a slight increase in the 2015 compared to the 2014 index, which is the lowest in the series. Viewed overall, and pending the development of an OMP to take the assessment uncertainties into account in a better manner, a TAC increase (if any) for the 2016/17 season would seem best to be kept small. 

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Department/Unit

Department of Mathematics and Applied Mathematics, University of Cape Town