Metazoan parasites of Xiphias gladius (L. 1758) (Pisces: Xiphiidae) from Atlantic Ocean: implications for host stock identification.

The metazoan parasite fauna composition of the swordfish Xiphias gladius is reported from 157 fish caught in four areas of the Atlantic Ocean: northwest (NW), central north (CN), eastern tropical (ET), and central south (CS). Samples were collected in 2003, 2006, and 2007. In all, 18 parasite taxa were identified by morphological and genetic methods. These data, together with earlier analyses from the tropical equatorial (TEQ) Atlantic revealed the association of some parasite taxa with distinct areas based on their presence/absence and infection levels. Hysterothylacium corrugatum (s.l.) and Rhadinorhynchus pristis were mostly associated with swordfish caught in the NW, and Anisakis paggiae and H. incurvum with fish caught in the southern areas (ET, TEQ, and CS). Anisakis simplex (s.s.) could be used as a marker for all northern samples. Parasitological data on Atlantic swordfish seem to support the existence of at least two discrete stocks in the Atlantic, supporting swordfish genetic stock structure