A preliminary assessment of yield of Patagonian Toothfish, Dissostichus eleginoides, for Heard Island Plateau (Division 58.5.2) was done, using the standard CCAMLR methods, based on the result of a randomly stratified trawl survey completed between 16 April and 10 May 2003. The 2003 estimate of abundance of recruits indicates a continuation of a period relatively low recruitment since 1999. A minor revision to the recruitment series resulted in a relatively small reduction in the preliminary estimate of sustainable long-term yield assessed using the standard method. The preliminary estimate for 2004 was 2,680 t. Initial tests of length at age assumptions indicated that using a specified length at age vector that did not include growth beyond 15 years had only small effects on projected long term yields. Further work is required to evaluate the implications of current uncertainty in the rate of growth beyond this age at 58.5.2. Preliminary examinations of the effect of refinements to the design of the annual survey indicated some variability in survey catchability between years and suggest that it may be appropriate to adjust estimates of cohort strength for catchability where possible. The 2003 season saw the operation of the first commercial long line vessel in 58.5.2. An initial comparison of the length distribution of the catches suggest that the two gears sample a similar range of sizes. This initial comparison was somewhat confounded by the depth of the grounds fished by the trawl and long-line operations. Very few large (>1200 mm) fish were observed in the long-line catch. Further structured work is planned in conjunction with the commercial operators for the 2004 season to provide data for a more comprehensive comparison, and to sample greater depths that fished by the long line operator in the 2003 season.
Document Number:
WG-FSA-03/33
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Abstract