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    Risk assessment for the Antarctic starry skate (Amblyraja georgiana) in the Ross Sea

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    Numéro du document:
    WG-FSA-2023/50
    Auteur(s):
    Holmes, S.J., B. Finucci, J.A. Devine, and M.H. Pinkerton
    Soumis par:
    Nathan Walker (Nouvelle-Zélande)
    Approuvé par:
    Nathan Walker (Nouvelle-Zélande)
    Résumé

    The Scientific Committee identified skates as “priority bycatch taxa for which assessments of status are required”. Catch data from the Ross Sea region show that most (~90%) of the skate catch consists of Antarctic starry skate (Amblyraja georgiana) and that this species is the only one with enough mark-recapture data to estimate local biomass. We present updated biomass estimates and exploitation rates consistent with the CCAMLR decision rules for A. georgiana in the Ross Sea, providing a range of possibilities for biomass and exploitation estimates. Model uncertainties still exist, particularly around post-release mortality. Biomass and exploitation estimates were highly reliant on assumptions about mortality and recruitment steepness. Current exploitation was considered sustainable if initial release mortality is < 40% (where skates are cut off the line), irrespective of assumptions on tagging cohort treatment and across plausible extremes of natural mortality. We note that the following would reduce model uncertainties: (1) the planned year of skate tagging commencing in the 2027/28 season; 2) recording of skate injury condition at capture and release, and (3) research to improve post-release mortality estimates. We recommend Conservation Measure 41-01, Annex 41-01/C, paragraph 2(x) should remain as is to ensure skates are sampled.