Assessment of the toothfish (Dissostichus eleginoides) resource in the Prince Edward Islands vicinity to include data from 1997 to 2013, including tag-recapture data

Brandão, Anabela; Butterworth, Doug S

Assessment of the toothfish (Dissostichus eleginoides) resource in the Prince Edward Islands vicinity to include data from 1997 to 2013, including tag-recapture data

Working Paper

2014

Publisher

University of Cape Town

Department

Marine Resource Assessment and Management Group

Faculty

Faculty of Science

Abstract

The assessment of the Prince Edward Islands (PEI) toothfish (Dissostichus eleginoides) resource carried out by Brandão and Butterworth (2013) is updated to take into account further data available for 2013 and a revised CPUE standardisation in which several desirable improvements have been made. This update also incorporates 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 55-60% range. 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 the longline CPUE is well below model predictions. In these circumstances, perhaps recommendations to increase the TAC beyond 500 t should first await further trotline CPUE data.

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