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    Proportional recruitment and weight-length relationship for krill in Subarea 48.1 and 48.2 from RV Atlantida survey, 2020

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    Document Number:
    S. Kasatkina and S. Sergeev
    Submitted By:
    Dr Svetlana Kasatkina (Russian Federation)
    Approved By:
    Dr Svetlana Kasatkina (Russian Federation)


    Data  from catches of research trawl  were obtained in Subareas 48.1 and 48.2  during cruise  RV Atlantida  in 2020.  The number of krill measured (length, weight) from 179 trawl catches was about 20,000. The length ranges smaller 36 mm were used to define the proportional recruitment. Variability of krill length frequency distributions and proportional recruitment by stratum are shown. The proportional recruitment of krill in Bransfeed Strait stratum (BS) and the Elephant Island (EI) stratum was 0,617 and 0, 472, respectively. Variability of weight - length relationship by stratum were also obtained, and these relationship differ from  the known regression ( a=2, 236 x 10-6 , b=3,314)  that are used  in CCAMLR practice ( for example,  CCAMLR 2000 Survey, Survey 2019, RV Atlantida 2020; and other surveys). The sensitivity of conversion factor to the used weight-length relationship is shown. The use of the known relationship (a=2, 236 x 10-6, b=3,314)   may underestimates the conversion factors. It was shown that the conversion factors when using this relationship in comparison with the new relationship will result in underestimations of the krill density from 10 to 26% depending on the stratum. To our opinion it is necessary to revise the use weight-length relationships.