The diet and feeding habits of the sharpsnout seabream, Diplodus puntazzo, from the Gulf of Gabès were investigated using stomach contents of 490 specimens ranging from 12.6 cm to 26.1 cm total length in size and from 29.95 g to 230.83 g in weight collected from commercial catches between April 2008 and March 2009. Of the total number of examined stomachs, 279 were empty (%VI = 56.94). This percentage varied significantly with months, attaining a maximum in spring (74.88%) and a minimum in autumn (37.38%). Eight major taxa were identified (Plantae, Spongia, Tunicata, Echinodermata, Crustacea, Annelida, Mollusca and Teleostei) in stomach contents of D. puntazzo. Plants were the most important food source, constituting 89.88% of the total Index of relative importance. The other groups, such as teleosts, molluscs, crustaceans and annelids represented accessory food. Significant differences in diet were observed in relation to season. Plants were the most important food source item in all seasons, especially during the autumn. The estimation of trophic level gave an average of 2.57 ± 0.2 for the whole population of D. puntazzo in the Gulf of Gabès. Based on the composition of its diet, this species may be considered as an omnivorous fish with a preference for vegetable material, and showing specialist feeding strategy.

The fatty acid composition and lipid content of white muscle, liver and mesenteric fat, in reared v. wild sharpsnout sea bream (Diplodus puntazzo) were compared. The mesenteric fat index (100×mesenteric fat weight/body weight) and the lipid contents of both white muscle and liver proved consistently higher in farmed v. wild sharpsnout sea bream (79·0 (SE 13·1) V. 38·7 (se 5·1) g/kg, 188·4 (se 30·0) v. 58·2 (se 3·9) g/kg and 27·2 (se 3·7) v. 17·3 (se 1·9) g/kg, respectively). The higher values of linoleic, eicosapentaenoic, docosahexaenoic and n-3 series acids in reared fish muscle make reared sharpsnout more favourable for human consumption. In reared fish mesenteric fat, polyunsaturated fatty acids reached higher levels (32·54 (se 0·71) g/100 g total fatty acids than those found in wild fish (26·08 (se 1·38) g/100 g total fatty acids or even present in the diet (28·34 g/100 g total fatty acids). Compared with cultured fish, wild sharpsnout displayed a higher content of n-3 fatty acids in liver fat (31·67 (se 1·13) g/100 g total fatty acids), but lower in mesenteric fat (20·35 (se 1·41) g/100 g total fatty acids). Atherogenic index values were similar for wild and reared fish in all tissues, while the index of thrombogenicity of muscle and mesenteric fat (0·353 (se 0·012) and 0·402 (se 0·021) respectively) was significantly increased in wild fish probably due to the omnivorous habits of the species and/or to seasonal food variations. Depending on the time of the year or the season, reared fish could be more suitable for human consumption than wild fish.