Ontogenetic and seasonal feeding habits of the annular seabream (Diplodus annularis L.) in Zostera sp beds, eastern Adriatic Sea

The ontogenetic and seasonal feeding habits of 489 individuals of Diplodus annularis L. in Zostera sp. beds were studied using frequency of occurrence, numeric percentage, percentage by weight and an index of relative importance (IRI). The Schoener overlap index was used to compare diets by fish size and seasons. Diet composition including 18 different prey taxa was evidently heterogenous among annular seabream size groups, with no significant dietary overlap. In relation to body size, juveniles were omnivorous and preferred algae and plants, while adults were omnivorous and preferred animals. Principal prey items by decreasing importance were Chlorophyta (dominant taxa Cladophora sp. and Enteromorpha flexuosa), Decapoda (dominant species Upogebia pusilla), Gastropoda (important species Rissoa ventricosa and Alvania sp.), Bivalvia and Spermatophyta, as well as other food items (mostly unidentified Crustacea and fish eggs). Differences in diets among seasons were not significant.