The diet of pelagic loggerhead sea turtles (Caretta caretta) off the Balearic archipelago (western Mediterranean):: relevance of long-line baits

Gut content and stable isotope analyses were used to investigate the feeding habits of loggerhead sea turtles (Caretta caretta) inhabiting the Balearic archipelago. Turtles caught in the pelagic realm (delta C-13: - 16.0 +/- 0.6 %o and delta N-15: 8.5 +/- 0.9 parts per thousand) and turtles caught on the continental shelf (delta C-15: - 16.7 +/- 0.6 parts per thousand and delta N-15: 8.4 +/- 1.3 parts per thousand) did not differ in their isotopic signatures, suggesting that their diets include the same prey types. A mixing model revealed that for the turtles here analysed, squid and the jellyfish Coylorhiza luberculata were the most relevant prey, although stomach contents analysis revealed that carnivorous jellyplankton, neuston, fish and other cephalopods were also consumed. Gut content analysis also indicated that most of the prey identified, including all fish and most cephalopods, were of pelagic origin. Thus, loggerhead sea turtles inhabiting central regions of the western Mediterranean appear to seldom exploit benthic prey, even while on the continental shelf.