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    Preliminary assessment of the exploratory fishery for Dissostichus spp. on BANZARE Bank (Division 58.4.3b), based on the analysis of fine-scale catch and effort data

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    J.P. McKinlay, D.C. Welsford, A.J. Constable and G.B. Nowara (Australia)
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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 fisheries, the Scientific Committee requested urgent consideration by Members of methods for collecting data and of assessing these stocks.
    At its meeting in July 2007, WG-SAM agreed that fine-scale analysis of catch and effort would be a useful way of progressing an assessment of BANZARE fishery (WG-SAM 2007, paragraphs 3.1-3.7), including:
    • Identification of grounds through analysis of spatial pattern in catch and effort;
    • Exploration of standardising CPUE series for each ground; and
    • Analysis of CPUE of Dissostichus spp. to provide initial estimates of biomass and rates of depletion in each ground.
    This paper develops further the initial exploration of the C2 fine scale catch and effort data held by CCAMLR for the fishery in this Division presented to WG-SAM in 2007, as well as descriptive analyses of the B2 biological data submitted by scientific observers aboard vessels in the BANZARE fishery.
    Data were too few, or with insufficient overlap between seasons, to permit meaningful standardisation for depletion analysis. However, these preliminary analyses indicate there is strong evidence for depletion of toothfish at the scale of individual fishing grounds in 2004/05 and 2005/06 seasons. There are also several inconsistencies noted between historical catch rates and catch compositions and those reported in the 2006/07 season, with Patagonian toothfish dominating in catches in one ground for the first time, and some observers reporting no biological information on important bycatch groups reported in the vessels catch records.
    We recommend that WG-FSA evaluate management options in 58.4.3b, including the lowering of catch limits commensurate with the rapid and unsustainable depletion seen in the fishery, the development of SSRUs to better represent the concentrated nature of the fishery in 58.4.3b, commensurate management of areas that are obviously depleted, and the design of a longline survey to attempt to verify some of the trends in catch rates and catch composition seen in the main fishing areas.