The flathead grey mullet, Mugil cephalus (Linnaeus 1758), and the golden grey mullet, Chelon auratus (Risso 1810), are two species of fish belonging to the family Mugilidae with commercial importance in tropical and warm temperate estuaries (Blaber, 1997) and an important ecological function in food chains (Cardona, 2001). Unfortunately, nowadays, the status of mugils is very fragile due to continuous pollution from agricultural and industrial activities and also high fishing pressure. In fact, M. cephalus is a species that is becoming rare and endangered (Glamuzina and Bartulović, 2010). Several authors have previously published important studies on