Feeding habits of the common two-banded sea bream, Diplodus vulgaris (Sparidae), in the eastern Adriatic Sea
The feeding habits of the common two-banded sea bream, Diplodus vulgaris, from the eastern Adriatic were investigated with respect to fish size and seasons. Stomach contents of 728 specimens, 12.1-34.0 cm TL, collected by beach seine from 1999 to 2001, were analyzed. Of the total number of stomachs examined, 134 were empty (18.1%). This percentage varied significantly by season with a maximum number of empty stomachs recorded during the autumn (35.5%) and a minimum number recorded during the summer (4.5%). A total of 42 different prey species belonging to eight major groups: Echinoidea, Decapoda, Bivalvia, Gastropoda, Polychaeta, Mysidacea, Polyplacophora and Amphipoda were identified in stomach contents. Echinoidea constituted the main prey (%IRI = 40.9), especially for fish less than 25.0 cm TL. With fish growth, the proportion of echinoids decreased while that of decapods crustaceans and bivalves increased. The mean weight of stomach contents increased significantly for fish larger than 25.0 cm TL, while the mean number of prey items significantly declined. Diet composition showed a seasonal variation; echinoids were the most important prey item in autumn, winter and spring, whereas decapods were the most important prey item during summer. The lowest intensity of feeding was recorded during spawning (autumn) as well as in a period of lower sea temperature (winter). The mean weight and mean number of prey significantly increased in spring and summer. The results indicate that the common two-banded sea bream feeds on a wide range of prey items and can be considered an opportunistic predator.