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    Assessment models for Patagonian toothfish in research block 58.4.3a_1 of Division 58.4.3a, Elan Bank for the years 2005-2014

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    Document Number:
    K. Taki (Japan), S. Mormede (New Zealand) and T. Ichii (Japan)
    Submitted By:
    Ms Chika Fukugama (Japan)

    We made two sensitivity runs of age-structured and two fisheries (≥1300 m and < 1300 m) CASAL models for stock status assessments of Dissostichus eleginoides in the research block 58.4.3a_1 following the recommendations of the WG-FSA-2014 meeting. Two runs were carried out: including or excluding the data from fish tagged in 2012.

    The likelihood profiles for tagged fish released in 2012 for ELAN_1 model reflected a large number of recaptures of the tags released concentrated in the western area of research block. This is why the removal of 2012 tag release data boosted the MPD estimate of B0 in ELAN_2 model. The selectivity of the shallow fishery is poorly estimated in MCMC runs for ELAN_1 model. This is unsurprising as the length frequency of the shallow fishery presents two shifting modes in most years, and therefore cannot be fully fitted.

    We recommend that the more conservative model (including the 2012 tag data) be used for management purposes. The median MCMC estimates of the initial and current biomass were 560 and 420 tonnes and the CCMLR yield for this stock was calculated at 27t.