Diet of Minke Whales Balaenoptera acutorostrata in the Northwestern Part of the North Pacific in Summer, 1994 and 1995

Abstract

The forestomach contents of 114 minke whales Balaenoptera acutorostrata randomly sampled in the northwestern part of the North Pacific in the summer of 1994 and 1995 were analyzed. Twelve prey species consisting of 7 fishes, 4 euphausiids and 1 copepod were identified. Pacific saury Cololabis saira was the most important prey species, occurring in 77.2% of the stomachs and composing 80.6% of the weight ingested, with some spatial and temporal variation. Japanese anchovy Engraulis japonicus was the next most important prey species, occurring in 14.0% of the stomachs and composing 6.7% of the weight ingested. Diurnal changes in the mean forestomach content weight and in the relative freshness of the forestomach contents showed little change between 06:00-18:00 h. The minke whales fed mainly on pelagic schooling fishes at the surface in the daytime.