An estimate of the quantity of squid consumed by seabirds in the eastern North Atlantic and adjoining seas

Abstract

A simple bioenergetics model provided estimates of annual squid consumption by seabirds as 40 000 t in the NE North Atlantic, 63 000 t in the SE North Atlantic and 3000 t in the Mediterranean. Squid was estimated to represent only 1% (by mass) of the diet of seabirds in the NE North Atlantic but 16% of the diet of seabirds in the SE North Atlantic. Main consumers of squid were fulmar and Manx shearwater in the NE and Cory's shearwater in the SE and Mediterranean. In general, procellariiforms tended to be the major seabird consumers of squid in all parts of the world. In comparison with studies in the Pacific and in the southern hemisphere (466 000 t of squid eaten by seabirds at south Georgia and 223 000 t of squid represent 54% of seabird diet at Hawaii), squid formed a notably small part of the diet of NE North Atlantic seabirds. Comparisons between diets of the same species in west and east Atlantic populations also showed less squid in NE North Atlantic seabird diets, suggesting that this may be at least in part a result of differences in prey availability.