Diet of Spondyliosoma cantharus and Diplodus puntazzo (Sparidae) in the Eastern Central Adriatic
The stomach contents of Spondyliosoma cantharus and Diplodus puntazzo were analysed using three simple methods (numeric, gravimetric and frequency of occurrence) and a composite index (IRI - Index of relative importance). To compare the species, the Schoener index was used. The diet of S. cantharus consisted mainly of amphipods followed by polychaetes, ophiuroids and hydrozoans, while macrophyta, bivalves, spongids, polychaetes and ophiuroids dominated in the case of D. puntazzo. There were some size-related differences in S. cantharus and D. puntazzo feeding. Diet overlap was high and significant between species. Polychaetes were the dominant prey group in all seasons for S. cantharus, particularly from spring to autumn. Significant differences among seasons were found for polychaetes, amphipods, ophiuroids and decapods. Mean weight and mean number of prey significantly increased to spring-summer period. Macrophyta and bivalves were the dominant prey groups in all seasons for D. puntazzo, particularly from spring to summer. Significant differences among seasons were found for macrophyta, bivalves, ophiuroids and hydrozoans. Mean weight and mean number of prey significantly increased to spring-summer period.