Occurrence of Polyprion americanus under floating objects in western Mediterranean oceanic waters, inference from stomach contents analysis

Catches of 11 juvenile specimens of Polyprion americanus (Osteichthyes: Pol yprionidae) are reported under fish aggregation devices (FADs) in waters of f Mallorca (western Mediterranean). Sampling was carried out fortnightly by surrounding artificial FADs with a purse seine from April 1995 till Februa ry 1997. Juveniles were present from June-August. Specimens were mostly sol itary during the period of association to the FADs, with a length interval of 25.8 and 34.2 cm total length. The trophic spectrum was analysed to expl ain a possible food link with the FAD. The diet of Polyprion was mainly bas ed on juvenile fish Trachurus and the cunestonic isopod Idotea metallica th at were associated with the objects providing evidence for a trophic relati on to the artificial structures.