Growth and age validation in high-Antarctic fish

Abstract

The growth of three demersal species dominant in biomass and abundance in the 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 polished otolith sections and an image analysis system to measure the otolith radius and distances of each growth increment to the otolith core. Ageing precision and accuracy have been estimated. Indirect validation methods, based on the increment growth pattern, were applied to support the annual periodicity of the increments. Due to the lack of some age classes, back-calculated age-length keys were determined and used to fit the von Bertalanffy growth parameters by sex and species. The determined values showed sexual dimorphism, with females having faster growth rates, except in D. longedorsalis. The growth performance index was between 1 and 2, as in other high-Antarctic 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-Antarctic fish age determination.