Ho. Acuna et Jm. Francis, SPRING AND SUMMER PREY OF THE JUAN-FERNANDEZ FUR-SEAL, ARCTOCEPHALUS-PHILIPPII, Canadian journal of zoology, 73(8), 1995, pp. 1444-1452
The composition of Juan Fernandez fur seal (Arctocephalus philippii) p
rey was assessed through analysis of 437 seats collected during five r
eproductive seasons (1987-1991). In total, 14 collections were analyze
d and, based on 4172 fish otoliths and cephalopod beaks, 13 prey speci
es were identified. The occurrences of fish families were as follows:
Myctophidae (80.3%), Scomberesocidae (10%), Carangidae (9.5%), Engraul
idae (1.0%), and Bathylagidae (0.7%). Cephalopod families included Ony
choteuthidae (27.1%), Ommastrephidae (3.7%), and Tremoctopodidae (0.7%
). In one year when data were available, Symbolophorus sp. B was found
more frequently in subadult male and juvenile seats than in female se
ats (P < 0.004). Female seats contained larger numbers of the squid On
ychoteuthis banksi than did subadult male and juvenile seats (P < 0.00
01). When collections made in early December were compared, the occurr
ence of O. banksi in subadult male and juvenile seats differed signifi
cantly between years (P < 0.0001). Within-year variations in occurrenc
e were significant only for O. banksi in 1989. The data suggest that t
he narrow range of species preyed upon by Juan Fernandez fur seals is
unlikely to represent specialization, but is probably related to overa
ll prey availability in the pelagic environment. Although information
on marine communities in this area is limited, it is possible to relat
e observed prey shifts to variations in sea-surface temperature.