FORAGING CHARACTERISTICS OF FEMALE NORTHERN FUR SEALS (CALLORHINUS-URSINUS) AND CALIFORNIA SEA LIONS (ZALOPHUS-CALIFORNIANUS)

Northern fur seals usually foraged in the oceanic zone where the mean water depth was 933 m. California sea lions principally were found in the neritic zone, where water depth averaged 323 m. Most fur seals (92%) of the island. Although both species evidently foraged at similar distances from the island, foraging trips of fur seals (mean 180.6 h) were over twice as long as those of sea lions (mean 73.4 h). Fur seals were ashore less time (mean 39.6 h) than were sea lions (mean 50.1 h) between foraging trips. Analysis of scats revealed that fur seals and sea lions ate similar prey (northern anchovy Engraulis mordax, Pacific whiting Merluccius productus, juvenile rockfish Sebastes spp., market squid Loligo opalescens, and nail squid Onychoteuthis borealijaponicas), although the relative proportions of these prey differed. Factors influencing the observed foraging characteristics probably were availability of prey and phylogenetic constraints associated with life-history traits. -from Authors