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    Extending the time series of catch-weighted length frequencies

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    Número de documento:
    David Ramm & Lydia Millar
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    The standard procedure used to extract catch-weighted length frequencies can only make use of CCAMLR data for D. eleginoides in Subarea 48.3 collected in the seasons 1992/93 and from 1994/95 onwards. The procedure cannot use the earlier data collected between 1984/85 and 1991/93, and data from 1993/94 because of a mismatch in Flag State which presently occurs between the length and catch data. A new procedure was developed which can use the mismatched data. In addition, historic data from 1986/87 to 1988/89 were entered in the CCAMLR database. The new procedure and recent data entry have extended the existing time series of catch-weighted length frequencies for D. eleginoides in Subarea 48.3 by nine (9) seasons. In all, data are now available for 21 seasons from 1984/85 to 2004/05. New data from the 2005/06 season will be added as soon as submitted. A comparison between the standard procedure and the new procedure indicates that the catchweighted length frequencies are similar where there is an overlap of seasons. However there is a systematic difference in the overall number of fish estimated each season. The basic procedure generally estimates fewer fish than the standard procedure and the difference between the two procedures is typically 5-10% (range: 1 to 34%). 

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