Diet composition of the bogue, Boops boops (Sparidae) from the Gulf of Annaba (Algeria).

Boops boops (L., 1759) is a common sparid along the Algerian coast. This study concerns composition and variations of its diet from the Gulf of Annaba (eastern coast of Algeria). The diet diversity of the bogue was studied during all annual cycle, between January 2005 and January 2006. Bogues were fished in deep sea using trawls and seine. The qualitative and quantitative analysis was realized according to sexes and to the various sampling seasons. A total of 665 individuals, ranging from 9.6 to 26.6 cm (TL), were examined. Digestive contents were analysed using three simple methods (numerical, gravimetric and frequency) and the main food index (MFI). Trophic activity was assessed monthly using the digestive vacuity coefficient (Cv). Spearman's coefficient of correlation was used to compare the qualitative composition of the diet according to the seasons and to the sex. During all the period of sampling, the digestive tracts were full, which corresponds to a null coefficient of vacuity. The voracity of this species differed between geographical areas. In the Mediterranean, with values of this coefficient obtained on Aegean Sea (Cv = 54.7%), different from those of the Gulf of Annaba. A total of 1780 preys were counted, belonging to 11 phyla. Boops boops is an omnivore fish and feeds on benthic (Crustacea, Mollusca, Annelida, Sipuncula, Plantae) and pelagic preys (Siphonophorae, Copepoda, eggs). The Chlorophyta algae represented a considerable part in its food. The use of the main food index indicated that any food item could ne considered as preferential or principal. All ingested preys were accessory. The statistical analysis of the digestive contents, according to the coefficient of range of Spearman, revealed significant changes in the diet in spring. No change of its diet has been observed according to the sex. The variations of its diet indicated the opportunistic character of this predator as in numerous regions of Mediterranean Sea.