Juvenile production of Atlantic bluefin tuna (Thunnus thynnus) is characterized by high mortalities and low growth rates during the larval stage. Startfeeding of Bluefin tuna larvae in hatcheries depends on the traditional food organisms rotifers and Artemia nauplii (Biswas et al., 2006), and skeletal malformations have been observed in 70% of larvae and juveniles (Libert et al., 2013). When copepods are used as live food, the results are generally improved compared to the use of traditional live feed organisms (Evjemo et al., 2003), with higher survival, increased growth, normal development, earlier onset of ossification and less skeletal anomalies compared to larvae fed rotifers and Artemia (Imsland et al., 2006). The aims of this study were to describe the bone development in the Atlantic Bluefin tuna fed copepods, and to evaluate the effects of start-feeding with enriched rotifers or with cultivated copepods on skeletal deformities.