LAUSR

The effects of sex, age, and environment on the shape of the bastard grunt (Pomadasys incisus) otoliths from the north-western Mediterranean were investigated. Specimens of this species were collected from two separate sampling areas in the north-western Mediterranean with different thermal regimes. Sex, growth rates, and age of P. incisus were determined by using gonad histology techniques, biometric analyses, and otolith microstructure analyses, respectively. The shape was described using normalized Elliptic Fourier descriptors (EFDs), and studied by means of multivariate statistics as predictive variables with age-specific discriminant analyses. There were no consistent differences found between sexes, but otolith shapes varied significantly between environments within different age classes. Total classification success varied between 87.3% and 89.2% between environments for the different age classes and provided a phenotypic basis for P. incisus population separation within an environmental gradient in determining its otolith shape. In addition, significant differences were observed between sampling areas in von Bertalanffy’s growth parameters, as well as in the fish length-weight (LWR) and fish length-otolith radius (TL-Ro) relationships. Data was discussed considering that the physical habitat variability could underlie a marked change in otolith shape during the animals’ growth. In this matter, we discussed the relative importance of both ontogenetic and environmental conditions (such as water temperature) on otolith shape.