Otolith Morphology: A Hidden Tool in the Taxonomic Study of Goatfishes (Teleostei: Perciformes: Mullidae).

Goatfishes (Teleostei, Mullidae) are a group of mainly coastal fishes that form an important part of food chains, and also have commercial value. In the marine waters of Iran, they are found in the Persian Gulf and Oman Sea (Gulf of Oman). This study evaluated whether otolith morphology can be used to distinguish of species and genera, and also to interpret whether otoliths of the same species differ among two studied marine systems. To do this objective, the otolith morphology of ten species belonging to three genera were analyzed by SEM photography and shape analysis. Among the morphometric variables, relative rostrum length was found to be the most important otolith variable for discriminating Mulloidichthys (RRL = 32.29 ± 0.59) and Parupeneus (RRL = 37.39 ± 1.10), while rectangularity (REx) was the most important shape index for discriminating Mulloidichthys (REx = 0.99 ± 1.94) from Parupeneus (REx = 0.77 ± 1.21). By considering otolith morphology, Upeneus showed a better separation than the two other genera. The otoliths of Upeneus are diagnosed by short dorsal length (RDL = 69.35 ± 1.51), higher rostrum height (RRH = 53.63 ± 1.99), short rostrum (RRL = 31.12 ± 1.99), and antirostrum lengths (RanL = 12.38 ± 1.51). The most diverged phenotype within the genus Parupeneus was found for the otoliths of P. rubescens, and the most diverged phenotype within the genus Upeneus was found for the otoliths of U. sundaicus. The otoliths of the same species did not demonstrate large variation between the Persian Gulf and the Gulf of Oman. This study provides additional morphological evidence for the separation of goatfishes at the species and genus levels. We also underline that the slight observed differences between the otoliths of two marine systems are mainly caused by the ecological differences known between these two main systems.