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    A preliminary assessment of age and growth of Antarctic silverfish (Pleuragramma antarcticum) in the Ross Sea, Antarctica

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    Numéro du document:
    WG-FSA-10/20
    Auteur(s):
    C.P. Sutton and P.L. Horn (New Zealand)
    Résumé

    Antarctic silverfish (Pleuragramma antarcticum) were sampled during a trawl survey in the Ross Sea, Antarctica. Biological data, including fish length, weight, sex, gonad maturity, liver weight and diet analysis were collected from 311 specimens. Standard length and weight were well correlated (r2 = 0.99).

    Counts of growth zones in 304 thin-sectioned otoliths were used to estimate ages and von Bertalanffy growth parameters. The species is relatively slow-growing with a moderate longevity; the maximum estimated age was 14.3 years. Von Bertalanffy parameters derived for both sexes combined are: L, 22.1 cm SL; K, 0.167 y-1; t0, -0.4 years. Parameter estimates were also derived for the sexes separately. Female Antarctic silverfish appear to reach a larger size than males, but none of the estimated von Bertalanffy parameters were statistically significantly different between sexes. All parameter estimates are preliminary as the ageing method is unvalidated and about two-thirds of the sampled fish could not be sexed.

    Precision estimates and age bias plots indicated that there was good within-reader and between-reader agreement, so the otolith sections appear able to be consistently interpreted.

    The standard lengths of the sampled Antarctic silverfish ranged from 4.6 cm to 22.9 cm. Pronounced modes in the length-frequency distribution occurred at 7.1–7.5 cm, 10.6–11.0 cm, and 15.1–15.5 cm. The age-frequency distribution exhibited a mode from age 6 to 9 years.