Food composition and feeding habits of little tunny, Euthynnus alletteratus (Rafinesque, 1810), from the Tunisian Mediterranean coasts

Abstract

The stomach contents of 622 little tunny Euthynnus alletteratus, sampled between January 2008 and December 2009, were examined. Fish size ranged from 19.2 to 97.8 cm fork length, and all fish were captured in the coastal areas of Tunisian waters. Among 622 stomachs examined, 287 were empty (%VI = 46.14). There were no significant variations in the vacuity index (%VI) depending on sex. After the stomach contents analysis, 22 prey taxa belonging to 14 families were identified: 15 fish species, 3 crustaceans, 3 mollusks and 1 vegetal species (Posidonia oceanica). This study was based mainly on the evolution of the index of relative importance (IRI) with respect to sex, fish size and season. Little tunny are carnivorous fish that feed opportunistically. Teleosts were found in the majority of stomachs, with a total relative importance (%IRI) of 97.3% and Sardinella aurita was the most important prey species (%IRI = 17.56) followed by Boops boops (%IRI = 0.87) and Sardina pilchardus (%IRI = 0.77). All other prey (crustaceans and molluscs) are secondary or incidental.