What cephalopod remains from Xiphias gladius stomachs can imply about predator-prey interactions in the Mediterranean Sea? P. PERISTERAKI*†, G. TSERPES* AND E. LEFKADITOU‡ *Hellenic Centre for Marine Research, Crete, P. O. Box 2214, 71003 Iraklion, Greece and ‡Hellenic Centre for Marine Research, Athens, 16604 Helliniko, Greece (Received 17 June 2004, Accepted 14 February 2005) Analysis of the cephalopod beaks found in the stomachs of 69 swordfish Xiphias gladius caught in the Aegean Sea resulted in the identification of nine cephalopod taxa. Cephalopod consump- tion was higher in summer and autumn, and larger swordfish were more likely to feed on cephalopods. Todarodes sagittatus was the most abundant species, a finding suggesting its abundance in the Mediterranean sea. # 2005 The Fisheries Society of the British Isles Key words: cephalopod beaks; feeding behaviour; Mediterranean sea; swordfish. The swordfish Xiphias gladius L. is a large predatory and highly migratory fish, globally distributed between the latitudes 45  N to 45  S and found mainly in the open sea. Mediterranean swordfish populations constitute a unique stock, distinct from the Atlantic ones with different growth and maturity characteristics (Tserpes & Tsimenides, 1995). A recent assessment carried out by the International Commission for the Conservation of Atlantic Tunas (ICCAT) estimated the total biomass of the Mediterranean stock to be c. 40000 t (Anon, 2003). Though swordfish diet has been described by many authors (Scott & Tibbo, 1968; Stillwell & Kohler, 1985; Moreira, 1990; Hernandez- Garcia, 1995; Clarke et al., 1996), only a few studies have been done in the Mediterranean Sea (Bello, 1991; Peristeraki & Tserpes, 2001; Salman, 2004). The studies mentioned above have shown that swordfish mainly feeds on small pelagic fishes and cephalopods. Some of the cephalopod prey are pelagic species, rarely caught by man and consequently poorly studied. The present work is based on the analysis of loose cephalopod beaks found in the stomachs of swordfish individuals caught in the south Aegean Sea with the aim of improving the understanding of the feeding ecology and behaviour of swordfish in the Mediterranean Sea. †Author to whom correspondence should be addressed. Tel.: þ30 2810 337830; fax: þ30 2810 337820; email: notap@imbc.gr Journal of Fish Biology (2005) 67, 549—554 doi:10.1111/j.1095-8649.2005.00742.x, available online at http://www.blackwell-synergy.com 549 # 2005 The Fisheries Society of the British Isles