The total number of fish species catalogued for the Iberic Mediterranean Sea (Balearic and Alboran Sea), consists of 519 which are found throughout the year or are seasonal in the water column and at the bottom ranging between 0 and 1050 meters deep. The above mentioned depth range is where the three congeneric species belonging to the family Carangidae (Trachurus mediterraneus, Trachurus picturatus andTrachurus trachurus),considered as middle sized pelagic fishes, develop their respective life cycles. These species may overlap in an interval of the water column. This overlapping contributes to obscure their habits in such a way that, from the statistical and fishery point of view, they are usually considered as a single unit (Trachurus spp.), thus ignoring their true distributional pattern. In fact, each of the Trachurus species is very precisely related with a group of fish acting as indicators of a particular niche. This diversity makes the differentiation among habitats a way to distinguish the different Trachurus species, and thus attenuates any kind of intercongeneric competition or rivalry.