TIZO Diet composition of juveniles of rough ray Raja radula (Chondrichthyes: Rajidae) from the Ionian Sea

Abstract

The diet of juvenile specimens of Raja radula from the Ionian Sea was investigated. The stomach contents of 43 specimens were analysed in order to evaluate composite index (IRI Index of Relative Importance). To assess feeding strategy and trophic niche width, prey-specific biomass plotted against frequency of occurrence and Levins index were used, respectively. The diet of juvenile specimens of R. radula consisted mainly of crustacean decapods followed by algae, polychaetes and molluscs. Among crustaceans, Liocarcinus spp. were the most important prey items, with four species with relatively high IRI values. Most specimens had been feeding on L. pusillus, L. depurator and polychaetes, but the variation of prey-specific biomass indicates that there is not a clear dominance of any prey and the value of niche width indicates a high variability in R. radula diet. Differences between sexes exists only in % IRI values related to Liocarcinus spp. The results indicate that R. radula feeds on a wide range of prey items, although crustaceans were the favoured food source. © 2010 Unione Zoologica Italiana.