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    A preliminary assessment and revised growth model of mackerel icefish (Champsocephalus gunnari) in Division 58.5.2, based on results from the 2017 random stratified trawl survey

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    Document Number:
    D. Maschette, P. Burch, P. Yates and D. Welsford
    Submitted By:
    Dr Philippe Ziegler (Australia)
    Approved By:
    Dr Dirk Welsford (Australia)

    The annual random stratified trawl survey was undertaken in Division 58.5.2 in the vicinity of Heard Island and the McDonald Islands during April 2017. This paper provides an updated growth model and a preliminary assessment for mackerel icefish (Champsocephalus gunnari) population structure, abundance and yield in Division 58.5.2 to the west of 79o 20’ E using standard CCAMLR methods (CMIX and Generalized Yield Model).

    The 2017 survey showed a large 3+ cohort dominating the population. An updated growth model based on recent cohort progressions indicated an increase in size-at-age compared to the estimates of Welsford (2010), however Generalized Yield Model projections indicated that the updated growth parameters resulted in only a small impact on yield.  Catches of 526 t in the 2017/18 season and 395 t in the 2018/19 season respectively satisfied the CCAMLR decision rules. Given their apparent plasticity in growth, we recommend that growth parameters used in assessments be updated routinely.