Role of pelagic crustaceans in the diet of the longnose lancetfish (Alepisaurus ferox) in the Seychelles waters

International audienceThe role of the pelagic crustaceans in the diet of the longnose lancetfish (Alepisaurus ferox) was investigated through the analysis of stomach contents collected in the waters surrounding the Seychelles Archipelago. Crustaceans accounted for 88.4% by prey number and for 73.7% by reconstituted mass during the South-West monsoon. During the North-East monsoon, they remained the main prey group and accounted for 63.7 % by prey number and for 46% by reconstituted mass. A clear seasonal pattern was apparent, with the portunid crab Charybdis smithii predominating during the South-West monsoon and the stomatopod Natosquilla investigatoris during the North-East monsoon. The observed changes probably reflect variations in prey availability linked to current movements occurring in this part of the western Indian Ocean. Most of the prey consisted of slow swimming and small individuals, known to live in dense swarms during their pelagic phase. In pelagic Seychelles waters, the trends observed in the diet of lancetfish are consistent with opportunistic feeding on the most abundant prey. It exploits short food chains based on carnivorous crustaceans. Such results emphasise the role of pelagic crustaceans in the trophic chain of the western part of the Indian Ocean