Feeding habits of Mediterranean horse mackerel, Trachurus mediterraneus (Carangidae), in the central Adriatic Sea

The feeding habits of the Mediterranean horse mackerel, Trachurus mediterraneus from the central Adriatic Sea, were investigated with respect to fish size and seasons. Stomach contents of 1200 specimens, 11.6 - 38.0 cm TL, taken at monthly intervals (January-December, 1996) were analyzed. Of the total number of stomachs examined, 606 were empty (50.5%). The proportion of empty stomachs varied significantly among size classes and seasons. Maximum feeding intensity occurred during the summer and in size class > 32.2 cm TL. The food composition suggests that the Mediterranean horse mackerel is a carnivorous species. A total of 29 different prey species belonging to six animal groups were identified in stomach contents: Crustacea (Euphausiacea, Mysidacea, Decapoda), Teleostei, Cephalopoda and Polychaeta. Euphausiacea were the most important ingested prey (%IRI = 90.1), especially in small and medium size classes (up to 28 cm TL). At the species level, euphausiids Nyctiphanes couchii (%IRI = 69.7) and Euphausia krohni (%IRI = 16.4) were the most frequent prey. Teleosts, whose proportion increased in large size classes, were secondary food (%IRI = 9.1), while other animal groups were considered as occasional food. The mean weight of stomach contents increased significantly for fish larger than 26.1 cm TL, while mean number of prey items did not differ among the size classes. There was little seasonal variation in food composition. Euphausiids were dominant prey during all seasons, and were especially abundant from summer to winter.