Belaoud T., Porteiro F.M. & Neves V. (2025) Presence of mesopelagic fish in the diet of two sympatric species of Storm Petrels. ARDEA 113 (2): 9-9

This study describes the mesopelagic fish present in the diet of two sympatric storm petrels, the summer breeding Monteiro’s Storm Petrel Hydrobates monteiroi and the winter breeding Band-rumped Storm Petrel H. castro. Prey species were identified based on otoliths obtained through stomach flushes. Fieldwork took place in 1998 and 1999 in three colonies of the Azores archipelago. 279 otoliths were found in 329 samples, corresponding to 8 fish orders, 11 families, 24 genera and 27 species. About one third of the otoliths (32%) could not be identified due to their eroded condition. Electrona risso was consistently the most abundant prey species in both years and for both seabird species. Myctophiformes, Argentiniformes and Beryciformes were present in the diet of the two storm petrel species. Gadiformes and Acropomatiformes were only present in the diet of Band-rumped Storm Petrel, while Perciformes, Trachichtyiformes and Stomiiformes were only present in the diet of Monteiro’s Storm Petrel. Storm petrels are surface feeders and the mechanism by which they can access mesopelagic prey is unknown. The otolith analysis allowed us to identify new fish species that were not described before in the diets of these storm petrels. Although there has been one previous study on these storm petrels’ diets, our study added 27 new prey species to the record. Mesopelagic fish are an important link between the components of the ocean food chain.