MEPS prepress abstract  -  doi: 10.3354/meps07355

ABSTRACT: Stable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine bird and fish communities from Reunion Island, western Indian Ocean. Firstly, isotopic signatures in the liver of Barau's petrels (Pterodroma baraui), Audubon's shearwaters (Puffinus lherminieri bailloni) and white-tailed tropicbirds (Phaethon lepturus) were used to compare their trophic levels and determine whether they forage in the same areas while breeding on Reunion Island. Spatial and trophic segregations were noted among these seabirds. Barau's petrels seem to feed on prey of higher trophic levels than Audubon's shearwaters. Different isotopic signatures in adults and juveniles of these species suggest that these chick-rearing Procellariiformes adopt a dual food-provisioning strategy, making separate foraging trips to feed their fledglings and for their own maintenance. However, satellite tracking should be undertaken to verify this hypothesis. Furthermore, novel data were obtained on the seabirds' interbreeding period by analyzing feather signatures. White-tailed tropicbird is thought to change foraging areas during this season although noen of the birds seem to shift diets. Secondly, isotopic signatures in the muscle of yellowfin tunas (Thunnus albacares), skipjack tunas (Katsuwonus pelamis) and common dolphinfish (Coryphaena hippurus) were used to gather information on their feeding behaviors in Reunion Island waters. Spatial and trophic segregations were also observed, particularly between common dolphinfish and the tuna species, the former feeding more under fish aggregation devices on low trophic level coastal organisms than the latter. Finally, trophic interactions in bird and fish communities were investigated. Seabirds appear to be trophically more structured than fish, foraging in a wider range of areas, although association for feeding was confirmed by our results, namely for Audubon's shearwaters and yellowfin tunas.