Sagittal otolith size and shape variability to identify geographical intraspecific differences in three species of the genus Merluccius

A study was carried out on the morphology (size and shape) of the saccular otolith (sagitta) by means of image analysis on three species of the genus Merluccius (M. gayi, M. hubbsi and M. merluccius). By digitization of the s agittae, morphometry and outline (Fourier harmonic) as form descriptor meas urements were obtained, that were subsequently analysed by means of multiva riant methods, allowing the intraspecific variability to be quantified. The differences in the intraspecific sagittal otolith variability confirmed sp atial differences of predicted groups. The results were associated with env ironmental and population aspects. The use of combined morphometric measure ments for the whole otolith and its corresponding sulcus acusticus were ver y appropriate for determining the origin of the analysed otoliths. Using bo th principal components analysis and discriminant analyses, a clear geograp hical differentiation was obtained for Merluccius gayi (from Chile and Peru ) and M. merluccius (from the Atlantic and Mediterranean). In both species, the discriminant analysis predicted that all the sagittae could be correct ly assigned within each of the groups studied. However, it was a little les s effective at differentiating between the two groups of M. hubbsi (from th e San Matias Gulf on the Patagonian Shelf and Argentinian-Uruguayan Common Fishing Zone). As a result, the morphometric analysis of the sagittae otoli ths acted as a clear diagnostic tool to differentiate individuals from diff erent geographical distribution areas.