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    An inter-laboratory comparison of ages estimated for Dissostichus eleginoides using otoliths

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    Document Number:
    WG-FSA-99/56
    Author(s):
    J. Ashford (United Kingdom) and P. Horn (New Zealand)
    Agenda Item(s)
    Abstract

    To examine consistency between laboratories in age estimation of Patagonian toothfish, otoliths were taken from 100 fish caught in the South Atlantic, and transverse sections prepared by baking, then grinding from the anterior and posterior sides of the otolith. Ages were estimated from the otoliths by one reader from the Center for Quantitative Fisheries Ecology at Old Dominion University and one reader from the National Institute of Water and Atmospheric Research, without auxiliary information: the readers generally read the sections similarly, with 84.7% of the estimates falling within two years or less of each other. Variation in estimates between readers did not increase markedly with age; however. the CQFE reader tended to give higher age estimates than the NIWA reader consistently over the full age range, indicating differences in the criteria used to interpret the first few years of age, possibly in identification of the first annulus.

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