2008 Volume 0 Issue 18 Pages 13-16
In spring, Pacific white-sided dolphin (PWS) come to the Tsugaru Strait, Sea of Japan, and is observed mostly in April and May. In this study, the data of sighting surveys conducted from ferry vessels between Hakodate and Aomori from May 2003 to August 2007 was analyzed. Differences in the appearance period of PWS in various years in the strait were discussed. The number of PWS and other cetaceans observed, both groups and individuals, were counted, and the relationship was examined between the appearance of PWS and water temperature and between the appearance of PWS and of its typical prey, anchovy. The first appearance of PWS has become earlier from 2003 to 2007. The relationships of appearance time to water temperature and the high season of anchovy catch were suggested, and it supported past studies.