WG-SAM-07

Three Operating Models (OMs) reflecting an “Optimistic”, “Intermediate” and a “Pessimistic” current status for the toothfish resource in the Prince Edward Islands region are developed which take account of the different selectivities of past longline and pot fisheries. These models are used for trials of a candidate Management Procedure (MP) which could provide future TAC recommendations for Read More
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We modelled the ray population at South Georgia using a surplus production model implemented in a Bayesian framework. Catch and CPUE data were reconstructed for the time series 1985 – 2006 from a variety of sources, and included the consideration that since 2004 the practice of cutting rays off lines at the water surface should have increased survivorship of discarded rays, although this Read More
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An updated version of the Spatial Multi-species Operating Model (SMOM) of krill-predator-fishery dynamics is described. This has been developed in response to requests for scientific advice regarding the subdivision of the precautionary catch limit for krill among 15 small-scale management units (SSMUs) in the Scotia Sea, to reduce the potential impact of fishing on land-based predators. SMOM Read More
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A useful way of testing assessment methodology and related decisions is through the framework of management strategy evaluation and the simpler form of assessment strategy evaluation. Such a framework uses an operating model of the system to generate data against which the assessment model, or the entire management system can be evaluated against a number of suitably chosen performance Read More
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Since 2002, the Working Group on Ecosystem Monitoring and Management has been undertaking a work program to develop a management procedure for krill fisheries. To date, this has primarily focussed on subdividing the region-wide krill catch limit in the southwest Atlantic into small-scale management units through a number of workshops. Computer simulations are being used by WG-EMM to evaluate Read More
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This report presents the data and preliminary results from developmental model for Antarctic skates in SSRUs 88.1H, 88.1I, 88.1J, & 88.1K of the Ross Sea. The developmental model attempted to create a catch history of all skates and rays in the Ross Sea, and integrate these data with the available observational data (including tag-recapture data) into a single integrated stock assessment Read More
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Descriptive analyses of the toothfish tagging programme carried out in Subareas 88.1 and 88.2 since 2001 are updated. The paper provides a preliminary update of the tag-release and tag-recapture data that were presented at the October 2006 meeting of WG-FSA by including data from New Zealand vessels and preliminary data for other vessels that fished in 2007.
Release and recapture data Read More
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In this paper, we address a number of aspects of the model inputs and parameters of the Antarctic toothfish stock assessment for the Ross Sea fishery. In particular we review catch history, length-weight relationships, catch-at-length and catch-at age. In addition, we report some preliminary model runs that investigate the sensitivity of the 2006 stock assessment to changes in these model Read More
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The incorporation of “effective sample size” (ESS) in integrated assessments is an approximate but simple way of modelling the distribution of catch-at-age or catch-at-length frequencies using a multinomial likelihood when there is extra-multinomial heterogeneity in age class or length class frequencies. The ESS applied within the definition of the negative log-likelihood contribution to the Read More
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In 2006 the CCAMLR scientific committee noted several features of exploratory Dissostichus fisheries in the southern Indian Ocean (58.4) which gave cause for concern as to the status of the resource in this area, and the lack of a scientific basis for setting catch limits in these areas (SC-CAMLR XXV, paragraphs 4.184-4.192).
In its management advice for this and other exploratory Read More
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An updated Antarctic toothfish (in the Ross Sea) stock assessment was done by means of the TISVPA model (2006 data on catch-at-age and cpue and the data on tag recaptures were included). All the three sources of information taken separately (and together) indicate historical increase in stock biomass, perhaps, due to development (broadening) of the fishery. The results show that, according to Read More
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