Diet of pilotfish, Naucrates ductor (Carangidae), associated with FADs in Sicilian waters (central Mediterranean).

Pilotfish, Naucrates ductor, are taken as a by-catch of the dolphinfish FAD (fish aggregating devices) fishery in Sicilian waters. In order to assess the diet of this poorly known species, the stomach contents of 80 specimens (between 21 and 29 cm SL) were analysed. Fishes were sampled between October 1994 and January 1995 on board of purse seiners fishing off NE and SE Sicily (central Mediterranean). Pelagic crustaceans (especially hyperiid amphipods) were the most abundant dietary item, followed by pelagic gastropods (Atlantidae) and fish larvae. Pilotfish seem to have a planktivorous diet up to a length of about 30 cm (age 6 months); larger specimens become unavailable to sampling, probably because they abandon floating objects and take an erratic attitude in open waters. The link of pilotfish with floating objects is still not clear, though several hypotheses (protection, visual stimulus and help in predation) are suggested.