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    Sensitivities in the assessment of the Patagonian toothfish (D. eleginoides) in Subareas 48.3 and 48.4 to truncation of tagging data

    Request Meeting Document
    Document Number:
    WG-SAM-17/35
    Author(s):
    T. Earl
    Submitted By:
    Dr Marta Söffker (European Union)
    Approved By:
    Ms Jane Rumble (United Kingdom)
    Agenda Item(s)
    Abstract

    The assessment of toothfish in CCAMLR subarea 48.3 currently uses the first four years of tag recaptures post release as input data, whereas the assessment in subarea 48.4 uses all available recapture data (excluding in-year recaptures). A theoretical analysis of the use of data from double-tagged recaptures suggests that including recaptures from fish at liberty for long periods will introduce bias into the assessment. Sensitivity tests on both stocks show that this bias occurs in practice. Sensitivity tests on the 48.3 assessment show that this bias is not entirely explained by the effect of double tagging.