WG-SAM-09

In 2008 WG-FSA recommended that the Secretariat undertake to identify the tagging event details for all tags recovered (WG-FSA 2008 paragraph 3.55). The Secretariat has been able to verify the tagging details of a greater proportion of tags than reported last year which has resulted in an improved proportion of the tags that can now be linked to tagging events in exploratory fisheries (Table Read More
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The level of data quality assessment and ‘certification’ as ‘fit for purpose’ depends upon the different requirements for the data, together with a recognition that, however thorough a validation exercise the data are exposed to, there will always be some data that require some additional confirmation of their validity. In the context of CCAMLR, data may undergo one set of quality testing in Read More
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The Secretariat allocated research hauls for exploratory fisheries in Subareas 48.6 and 58.4 in 2008/09, following the Scientific Committee’s guidelines. Some modifications were required to account for SSRUs where fishing had not been previously reported, and SSRUs where the number of positions reported in the fine-scale catch and effort data were insufficient to allow a bootstrap allocation ( Read More
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Integrated assessments that use catch-at-age or abundance-at-age data for model calibration require an ageing error matrix as input in order to adequately account for uncertainty in the data resulting from the imprecision of age determination using annual ring counts from otoliths. This paper describes the methods and results used to provide an ageing error matrix to the HIMI toothfish Read More
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Catch-at-age proportions are generally incorporated into an integrated assessment as observations that contribute to the objective function via a multinomial likelihood. The multinomial likelihood requires a nominal sample size for each fishery and year combination. A method is described for estimating an effective sample size (ESS) that can be used as the nominal multinomial sample size. The Read More
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The integrated assessment of Patagonian toothfish, Dissostichus eleginoides, for the Heard and McDonald Islands (Division 58.5.2) was updated by replacing catch-at-length proportions from commercial catches with catch-at-age proportions using age length keys (ALKs) where the ALK for each combination of fishery and year had available at least 50 aged fish. For the trawl fisheries that were Read More
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A survey was conducted in order to collect information for the stock status and various biological information on toothfish in Division 58.4.4a & b by using a commercial bottom longline vessel, Shinsei Maru No. 3, from July 23 to September 27, 2008. The survey was undertaken in two Phases (Phase 1 and Phase 2). Shinsei Maru Trot line system was used as a fishing gear. Toothfish contributed Read More
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In order to clarify stock status and biological characteristics of Dissostichus spp. in Division 58.4.4 a & b, a total of 124 research hauls are allocated on 10-minute latitude x 20-minute longitude grid points (spaced approximately 10 nautical miles apart). Almost all of the research hauls are distributed between 500 and 2,000 m sea depths over each SSRU, except only 2 hauls which are Read More
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An attempt to use CPUE data based on data of erussian observers in the assessment of Antarctic toothfish stock in division 58.4.1 is made. Unlike some previous results obtained for this division (e.g. WG-SAM-08/4), the assessment was intended to be independent of estimates of toothfich stock biomass in the Ross Sea. As a result of implementation of a dynamic production model, current biomass Read More
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The catch-at-age based CASAL model for toothfish in Subarea 48.3, which was presented in 2007, is developed and extended here to include survey data. Additional adjustments to the model suggested by WG-FSA-2007 are implemented. Fits to the survey length frequencies are good for recent surveys but in the past some cohorts have been missed by the survey. Fits to the survey CPUE are generally not Read More
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In this paper a simple biomass dynamic population model is used as a paradigm for the dynamics of toothfish spp. in the CCAMLR area. This model underpins a management strategy evaluation framework where the process of stock assessment, TAC calculation and implementation and potential changes in future toothfish productivity (continuous and regime-based) are all simulated. The robustness of the Read More
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The current assessment method for the mackerel icefish (Champsocephalus gunnari) in sub-area 48.3 employs the CMIX and GYM packages, deriving population numbers-at-age then projecting these numbers forward under the given harvest control rule to set a two-year TAC. One issue is the accurate identification of cohorts from the survey model, given the differential age structures observed in the Read More
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The ICESCAPE Software Users Guide (Appendix 1) describes a parametric bootstrap (Davison and Hinkley 1997) model for implementing the general abundance estimator proposed by Southwell (2004) for Antarctic land-breeding predators. The software, which was developed as a suite of routines in the R language for statistical computing (R Development Core Team 2008), aims to adjust raw count data for Read More
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The Spatial Population Model (SPM) is a generalised spatially explicit age-structured population dynamics and movement model. SPM can model population dynamics and movement parameters for an age-structured population using a range of observations, including tagging, relative abundance, and age frequency data. SPM implements an age-structured population within an arbitrary shaped spatial Read More
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We present developments towards spatially explicit age-structured population dynamics operating models for Antarctic toothfish in the Ross Sea. The operating models consider both a coarse-scale and fine-scale spatial resolution and consider scenarios where abundance can be present over the entire Ross Sea region or constrained to areas where the fishery has operated. The models represent Read More
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The suite of data quality metrics introduced by Middleton & Dunn (2008) is examined to identify those metrics that are most informative with respect to the identification of good tagging data. Trips considered to have “known” good tagging data are identified, based on above-median rates of recapture of tags released by the trip, and above-median tag recapture rates by the trip.A bootstrap Read More
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Acoustic and trawl samples obtained in the near-bottom layers covered by bottom trawl surveys in the South Georgia area are analyzed. The high heterogeneity of horizontal and vertical fish distribution in the near-bottom layers within the surveyed area is shown. Influence of this fish distribution heterogeneity on trawl surveys efficiency and reliability is analyzed by simulating the impact on Read More
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Bottom fisheries are now to ‘avoid significant adverse impacts on vulnerable marine ecosystems’ in order to maintain the ecological structure and function of, particularly, deep sea benthic habitats.  Noting the paucity of data on the ecology of these habitats, this paper provides a practical approach to develop and evaluate fishing strategies aimed at achieving this objective i.e. what Read More
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