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    Preliminary integrated stock assessment for the Antarctic toothfish (Dissostichus mawsoni) fishery in Divisions 58.41 and 58.4.2

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    Número de documento:
    Delegation of Australia
    Presentado por:
    Dr Philippe Ziegler (Australia)
    Aprobado por:
    Ms Doro Forck (Secretaría de la CCRVMA)
    Punto(s) de la agenda

    We present an update of ageing and estimates of biological parameters, and of the single-region integrated stock assessment for Antarctic toothfish (Dissostichus mawsoni) fishery in CCAMLR Divisions 58.4.1 and 58.4.2. The update of ageing and estimates of biological parameters addresses Milestone 1.4, the updated of the stock assessment addresses Milestone 1.6 of the current multi-member research plan for these Divisions (SC-CAMLR-39/BG/10).

    The assessment model used all data available from the region, supplemented with parameter estimates from other toothfish stock assessments. All evaluated assessment models indicated that the Antarctic toothfish stock in Divisions 58.4.1 and 58.4.2 is unlikely to be depleted by the current level of fishing mortality. Accounting for vessel tagging performance was highly influential in the estimates of B0 and SSB status, and we recommend further work to consolidate appropriate estimates of vessel-specific tag survival and detection performance.

    The model indicated unresolved issues with the tagging data and a systematic lack of fit to the catch-at-age data. The lack of directed fishing in Division 58.4.1 resulted in spatially-restricted data collected from a single research block in Division 58.4.2 over the last two fishing season. The models indicated that fishing gear has only a minor influence on catch-at-length and catch-at-age compositions and tag-recapture data in this Antarctic toothfish fishery, particularly relative to vessel and spatial population effects.

    Estimates of preliminary catch limits for the two Divisions indicated that the catch limits estimated by the trend analysis are precautionary.

    The collaborative approach adopted by the research plan proponents Australia, France, Japan, the Republic of Korea and Spain in Divisions 58.4.1 and 58.4.2 has worked well, with valuable on-water data collection and extensive subsequent data analyses. Based on these analyses, research has now progressed to a stock assessment, highlighting the value of the management procedures, agreed to by CCAMLR in 2011, which requires research plans in exploratory fisheries. However, an expansion of the spatial distribution of catch, tagging and data collection in Divisions 58.4.1 and 58.4.2 beyond a single research block will be required to improve estimates of stock biomass and catch limits in the future.