Food and feeding strategy of the thornback ray, Raja clavata, were studied from stomach contents analysis of specimens caught monthly in the Gulf of Gabes. The data were analysed according to sex, size and season. At total of 1280 stomachs was examined, from specimens ranging from 14 to 110 cm total length (TL), of which 1076 (83.98%) contained food. Thornback ray feed mainly on teleosts, crustaceans and cephalopods, whereas gastropods and polychaetes are occasionally consumed. Significant differences were found between the diets of males and females; however, ontogenetic changes were also detected, with crustaceans constituting the greatest proportion of the diet of smaller rays. Both teleosts and cephalopods increased in importance with growth of the skates. Prey diversity increased with size; large and mobile prey species were more commonly found in the diet of larger skates. Diet composition showed seasonal variations. Quantitative analyses and graphical methods indicate that the thornback ray is a generalist feeder.
Early life sensory ability-ventilatory responses of thornback ray embryos (Raja clavata
) to predator-type electric fields
