Growth and age validation in high-Antarctic fish

The growth of three demersal species dominant in biomass and abundance in t he Weddell Sea, Chionodraco myersi (channichthyid), Trematomus eulepidotus (nototheniid) and Dolloidraco longedorsalis (artedidraconid), was, studied on specimens caught in summer. Ages were determined using ground and polish ed otolith sections and an image analysis system to measure the otolith rad ius and distances of each growth increment to the otolith core. Ageing prec ision and accuracy have been estimated. Indirect validation methods, based on the increment growth pattern, were applied to support the annual periodi city of the increments. Due to the lack of some age classes, back-calculate d age-length keys were determined and used to fit the von Bertalanffy growt h parameters by sex and species. The determined values showed sexual dimorp hism, with females having faster growth rates, except in D. longedorsalis. The growth performance index was between 1 and 2, as in other high-Antarcti c fish. For T. eulepidotus, age and growth data were available, but this is the first report for C. myersi and D. longedorsalis. Moreover, this is the first time that accuracy and precision have been estimated for high-Antarc tic fish age determination.