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    Validating the Gasco-method for depredation estimation in Subarea 48.3

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    Document Number:
    M. Söffker and T. Earl
    Submitted By:
    Dr Marta Söffker (European Union)
    Approved By:
    Dr Chris Darby (United Kingdom)

    Depredation is experienced by several fisheries within the CCAMLR Area, however not all fisheries have a data collection programme that is sufficiently long established, or detailed, to allow for model estimation of the lost catch. A new method was developed in 2014 that used an observed change in ratios of toothfish to grenadiers on depredated longlines, and proved to estimate losses similarly to a depredation model. Here this method was adapted for Subarea 48.3 and compared to the outputs from an alternative long-standing model estimation approach feeding into the CASAL assessment for toothfish. The new method performed similarly to the established method both in estimating total losses, and identifying spatial patterns.