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    Revised 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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    Numéro du document:
    K. Taki (Japan), S. Mormede (New Zealand) and T. Ichii (Japan)
    Soumis par:
    Kenji Taki (Japon)

    We revised sensitivity runs of age-structured and two fisheries (≥1 300 m and < 1 300 m) CASAL models for stock status assessments of Dissostichus eleginoides in the research block 58.4.3a_1 following the recommendations of the last WG-SAM meeting. Total of four runs were carried out. Among them three runs were carried out using the latest information on age-length relationship in this division: two catch at length models including (ELAN_len model) or excluding (ELAN_tag model) the data from fish tagged in 2012, and a catch at age model including the data with a single age length key applied to all years (ELAN_age model). Another run was a catch at length model as ELAN_len model except using age-length relationship for Ob-Lena Banks (ELAN_lenOB).

    The likelihood profiles for tagged fish released in 2012 for ELAN_len, ELAN_age and ELAN_lenOB models 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_tag model. The selectivity of the right hand limb of deep fishery was poorly estimated in MCMC runs for ELAN_len model.

    The median MCMC estimates of the initial and current biomass for ELAN_len model were 330 and 260 tonnes and the CCMLR yield for this stock was calculated at 30 tonnes. The fishing bias to the shallow areas should be avoided because the CCAMLR risk 2 values at 13 tonnes and above for the shallow fishery exceed 50% toward the end of 35 year projection period in the model.