Ecomorfologia de otólitos de peixes como indicadores de uso de habitats estuarinos

Abstract

Estuaries exhibit high productivity and habitat diversity, and these structurally complex sets of habitats are used by estuarine fish in their early life stages. The aim of this study is to identify habitat use guilds and patterns in the otoliths of species found in estuarine habitats, as well as morphological variations of otoliths among estuarine habitats. Collections were made in three estuaries along the Alagoas coast in three habitats (seagrass, mangrove, and estuarine beach). Fish collected in these habitats were identified at the species level, and their otoliths were removed, cleaned, and photographed under a stereoscopic microscope. Using the shapeR package in R statistics software, Fourier descriptors were extracted from the digitized otoliths. To verify the existence of ecomorphological pattern clusters in estuarine habitats, the twelve harmonics were reorganized and reduced through principal component analysis (PCA). Using the PCA scores, Fisher's Discriminant Analysis (FDA) was applied to identify potential habitat-based groups. A PERMANOVA was used to test the significance of shape differences among otoliths in different habitats. Post hoc analysis was conducted to identify significantly differing groups. Ecomorphological patterns in the otoliths of juveniles characterizing estuarine habitats were detected through Fourier harmonics. The first ten principal components explained 92.98% of the variance. PERMANOVA and FDA indicated a significant difference between habitats (p = 0.002), with 25% of the confusion matrix not correctly classified. In pairwise comparisons, the seagrass habitat significantly differed from the mangrove (p = 0.001), while the estuarine beach habitat did not significantly differ from the mangrove or seagrass (p = 0.112 and p = 0.097), respectively. In conclusion, otolith analysis differentiated habitat groups based on shape even in the juvenile stage. Seagrass habitats are important for commercial species and ecosystem management.