Abstract
The coastal area off eastern Hokkaido, Japan, in the North Pacific, is an important foraging area for many seabird species in autumn. To understand the distribution of seabirds, in the shelf, slope and basin off eastern Hokkaido, ship-based censuses were carried out over three days from 27 to 29 September, 2003, on board the T/S Oshoro Maru (Hokkaido University, Fisheries Science). The warm (>19°C) Tsugaru Current affects the western area off Cape Erimo, while cold (<14°C) Oyashio Current affects the eastern area off the same cape. The density of seabirds sitting on the sea was high in the shelf and slope (including frontal area) areas influenced by the cold current where the primary productivity is usually high. Within these areas, densities of diving seabirds (Rhinoceros Auklet Cerorhinca monocerata and Puffinus spp) were high in the shelf area, whereas densities of surface feeders (Streaked Shearwater Calonectris leucomelas and Laysan Albatrosses Diomedea immutabilis) were high in the slope area.
