Squid in the diet of northern fur seals, Callorhinus ursinus, caught in the western and central North Pacific Ocean

The stomach contents of 89 northern fur seals (Callorhinus ursinus) caught in the western and central North Pacific from December to August during the period 1981-1994 were examined. In total 2567 items including 2401 beaks a nd 166 digested bodies of squid were obtained. Fifteen species from eight f amilies and four species from three families, respectively, were identified from squid beaks and bodies in the stomachs of seals from the western Nort h Pacific and the central North Pacific. Watasenia scintillans was numerica lly the dominant prey for northern fur seals in the western North Pacific, while Onychoteuthis borealijaponica and Ommastrephes bartramii tended to he important prey in the central North Pacific. Most of the squid prey were e stimated to be smaller than 150 mm dorsal mantle length (DML) except two in dividuals of Moroteuthis loennbergi and 10 individuals of O. bartramii. Mea n size of W. scintillans was almost constant from January to April at 42-44 mm DML. This suggests that northern fur seals feed actively on mature fema les of W. scintillans when they migrate to shallow waters for spawning duri ng winter and early spring in the western North Pacific, off Honshu, Japan. (C) 2001 Elsevier Science B.V. All rights reserved.