Geographic variation of shape and allometric relationship in sagitta otoliths of maria-luiza Paralonchurus brasiliensis (Steindachner, 1875) (Teleostei, Sciaenidae) from north of Rio de Janeiro coast (21º S - 23º S), Brazil

Abstract

The goal of this study was to analyze the shape differences and the allometric relationships in sagitta otoliths of Paralonchurus brasiliensis in order to assess the geographic variation among fish groups along the coast of Rio de Janeiro State. The specimens were collected in three contiguous areas with singular environmental characteristics: Atafona, Farol de São Tomé e Rio das Ostras. The otolith shape was measured by coordinates of reference points in the contour and the acoustic sulcus. A within-group regression of shape variables on otolith length was used for the study of allometry (shape variation caused by size changes) and the residuals were used in a discriminant analysis. The fish groups presented different allometric coefficients. The allometric pattern observed was associated with a positive growth along the anteroposterior axis and a relative increase in the ostium area. The discriminant analysis was significant and efficient in the identification of individual geographic origin. The morphological differences observed were related to environmental differences among sampled sites, particularly those associated with growth patterns and nutritional status. The combination of shape analyses and allometry of sagitta otoliths is useful for the identification of P. brasiliensis from Rio de Janeiro coast.