engleski

Diet and feeding strategy of thornback ray (Raja clavata Linnaeus, 1758) from eastern central Adriatic Sea

The diet and feeding strategy of thornback ray, Raja clavata, from the eastern central Adriatic Sea, were investigated. Stomach contents of 428 specimens, total length (TL) of 14.0 - 75.1 cm, collected from commercial bottom trawls from January to December 2009. were analysed. The prey items identified in the stomachs belong to eight major groups: Cephalopoda, Polychaeta, Stomatopoda, Decapoda (Natantia and Reptantia), Mysidacea, Isopoda, Amphipoda and Teleostei. Decapods were the most important prey (%IRI = 72.8) followed by teleosts (%IRI = 20.4), whereas other prey groups were only occasionally ingested. The fish size was the most important factor affecting diet. According to the observed ontogenetic shift, small sized individuals (< 25 cm TL) fed primarily on small crustaceans (mysids and amphipods), whereas large size specimens consumed bigger prey, such as decapods, cephalopods and teleosts. Diet composition showed little seasonal variation ; decapods were the most important prey in all season. Diet of R. clavata indicated high similarity between sampling locations. The percentage of empty stomachs did not differ significantly among size classes and seasons. In terms of composition by species, the diet of thornback ray was characterized by variety of rare or unimportant prey. As a result, thornback ray could be a considered as generalistic feeder.

feeding; thornback ray; Adriatic

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