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    Re-analysis of CPUE in both species of toothfish in 48.6 area

    Request Meeting Document
    Document Number:
    WG-FSA-13/63
    Author(s):
    R. Wiff, J.C. Quiroz (Chile) and R. Scott (United Kingdom)
    Submitted By:
    Sarah Mackey (CCAMLR Secretariat)
    Abstract

    The present report re-analyses data regarding CPUE for both species of toothfish in northern area of 48.6 (SSRU 48.6A, 48.6G). This report is a re-analysis of the CPUE time series proposed in previous work (SAM 13/29) which includes all those comments and suggestions made in the last SAM meeting. Here, the  length of the line was used as effort unit and also high CPUE values reported by a Korean Vessel (Insung No 7) were further investigated by applying extreme value analysis. Antarctic and Patagonian toothfish presented a high proportion with sets in which both species are present, and thus, an analysis of catch intention was implemented by using multivariate statistical approach of the catch composition. Standardisation of CPUE was done by using Generalised Additive Models (GAM) considering temporal and location factors. A mix model using vessel nationality as random variable was also implemented.  These improvements did not change the CPUE time series in Antarctic Toohthfish and only produces minor changes in Patagonian toothfish. We believe extreme value analysis provides a useful tool to evaluate anomalous CPUE.  The same conclusion with previous work arise, the CPUE have little or none information as index of abundance and thus, it is highly recommendable to continue with the collection of the data by scientific observed and tagging and release program.

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