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    A review of tag-based stock assessments of the Antarctic toothfish Dissostichus mawsoni in Subarea 48.4

    Request Meeting Document
    Document Number:
    N. Walker, M. Soeffker, V. Laptikhovsky and T. Earl (United Kingdom)
    Submitted By:
    Dr Chris Darby

    The stock abundance of Antarctic toothfish in Subarea 48.4 is estimated using tag based mark-recapture analysis. During WG-FSA-14 the recommendation was made that the stock should move from the Petersen estimation method to the use of the Chapman bias corrected estimator; a correction specifically developed to reduce estimation bias in populations with low recaptures, a feature typical of the data available for this species in 48.4. During a review of assessment methodology two main issues have been identified: the appropriate application of the method when applied to estimate low tag recapture rate population abundance, and the mis-identification of species at release. This paper presents a review of assessment data and methods in order to discuss and address the issues.