Abstract
In order to understand the environmental factors affecting the distribution of Rhinoceros Auklets at sea, ship-based censuses were carried out in the northern Sea of Japan off Hokkaido, during late May and early June 2005. Potential prey density was surveyed using acoustics: 38 kHz for pelagic fish and 200 kHz for plankton. Multiple regression analyses did not show any linear effects of prey density index, sea surface temperature, depth of the sea (water depth), or slope of the sea bottom, on the density index of Rhinoceros Auklets on the sea at any spatial scale (0.3–10 km). The density index for auklets was higher than expected around Teuri Island, Rebun Island, Ishikari basin and Musashi bank where the strength of marine currents seemed to be weaker than elsewhere, although differences were not statistically significant.
