Otolith shape analysis of the Brazilian silverside in two northeastern Brazilian estuaries with distinct salinity ranges

Abstract

The hypothesis that salinity and temperature influence otoliths of Atherinella brasiliensis populations was investigated by comparing the morphologies and shapes of otoliths from two contrasting estuaries (positive and hypersaline). Overall, 462 otoliths were extracted from adult fish collected in both estuaries. For each otolith, the morphometric measurements (height, width, and length) and were recorded. We compared the morphology and shape of the otoliths from Brazilian silversides in different estuaries and estuarine zones (upper and lower) using multivariate analyses of variance and discriminant function analysis. Overall, two morphotype patterns were revealed through elliptic Fourier descriptors based on 30 harmonics. Significant differences in the morphologies and shapes of otoliths were found among and within estuaries, particularly in the population from the hypersaline estuary, which presented higher otolith areas and perimeter and height values in comparison with that from the positive estuary. The otolith morphometric variables were correctly classified into their original groups at more than 98.3 %, indicating a high rate of correct classification of individuals into their original populations. The weight of the otoliths was inversely related to the condition factor of fishes. The results highlight the significant correlations of environmental variables on otolith morphology, with both temperature and salinity being significant drivers of differences between populations.