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    An integrated stock assessment for the Heard Island and the McDonald Islands Patagonian toothfish (Dissostichus eleginoides) fishery in Division 58.5.2

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    Número de documento:
    P. Ziegler and D. Welsford (Australia)
    Presentado por:
    Dr Philippe Ziegler (Australia)

    This paper presents an updated assessment for the Patagonian toothfish (Dissostichus eleginoides) fishery at the Heard Island and the McDonald Islands in CCAMLR Division 58.5.2 with data until end of July 2015. The updated assessment model is based on the best available estimates of model parameters, the use of abundance estimates from a random stratified trawl survey (RSTS), longline tag-release data from 2012-2014 and longline tag-recapture data from 2013-2015, and auxiliary commercial composition data to aid with the estimation of year class strength and selectivity functions of the trawl, longline and trap sub-fisheries.

    Compared to the 2014 assessment that was accepted by WG-FSA-14 to be used for management advice, this assessment takes into account the recommendations of WG-FSA-2014 and WG-SAM-2015, and incorporates (a) new fishery observations up to 2015 including new ageing data from the 2014-2015 RSTS and commercial fishery from 2009-2014, (b) tag-releases from 2014 and tag-recaptures from 2014 (complete) and 2015 (partial), (c) an updated growth model, (d) changes in priors for survey catchability q, unfished spawning biomass B0 and year class strength, and (e) a split of the trawl sub-fishery into two periods. All model runs were conducted with the CASAL version 2.30-2012-03-21 that was agreed on by WG-SAM-14.

    The updated assessment model leads to a smaller estimate of the virgin spawning stock biomass B0 than that obtained in 2014, with an MCMC estimate of 87 077 tonnes (95% CI: 78 500-97 547 tonnes). Estimated SSB status in 2015 was 0.64 (95% CI: 0.59-0.69). Using this model, a catch limit of 3405 tonnes satisfies the CCAMLR decision rules. Similarly to the 2014 assessment, the projected stock remains above the target level for the entire projection period.

    CASAL files are available here.