Diet composition and feeding intensity of horse mackerel, Trachurus trachurus (Osteichthyes: Carangidae) in the eastern Adriatic

Abstract

Diet composition and feeding intensity of the horse mackerel, Trachurus trachurus, collected in the eastern Adriatic Sea, were examined. Stomach contents of 1,200 specimens, taken at monthly intervals (January–December 1996), were analyzed. The stomachs contents consisted of five major prey groups: Crustacea (Euphausiacea, Mysidacea, Decapoda), Cephalopoda and Teleostei. Euphausiacea constituted the most important food resource by weight, number and frequency occurrence. Teleosts were the second most important food category, while mysids, decapods and cephalopods were occasional food. There was little seasonal variation in diet. Euphausiids were dominant prey during all seasons, and were especially abundant from spring and autumn. Feeding intensity of horse mackerel varied during the year. The lowest intensity of feeding was recorded in winter (February, March) and early spring (April) during the lower sea temperature as well as at the time of intensive spawning. Feeding activity increased upon spawning period (May and June) and was also higher during summer. Feeding intensity and diet composition changed during the diurnal cycle. The highest feeding intensity was recorded at night and during early morning hours. Euphausiids, mysids and a greater part of teleosts dominated night and morning diet, while decapods and cephalopods were most frequently in the daily and evening diet.