Feeding habits of the Atlantic bonito, Sarda sarda (Bloch, 1793) in the southern Tyrrhenian sea

The feeding habits of the Atlantic bonito Sarda sarda (Bloch, 1793) caught in the southern Tyrrhenian sea were studied. The specimens were collected by means of a surface gillnet on a monthly basis between March and December 2003. The importance of the different prey items was assessed utilizing several feeding indexes, while possible size-related and temporal variations of the diet composition were tested by means of DISTLM forward and NMDS analysis. Intact prey items were measured in order to determine predator–prey relationships. The results of this study showed that S. sarda is a piscivorous predator focusing on clupeiforms and more in detail on three species such as the round sardinella Sardinella aurita, the sardine Sardina pilchardus and the anchovy Engraulis encrasicolus. Other prey were recorded occasionally. No temporal significant variations in the diet composition were found. On the other hand, a variation in the diet of the Atlantic bonito was observed according to its length. The smaller specimens fed primarily on E. encrasicolus. As they grew, S. pilchardus and S. aurita became important prey species, with the latter becoming by far the predominant prey for the largest Atlantic bonitos. Finally, a significant and positive correlation between predator and prey length was found.