2013 Volume 23 Pages 29-33
The cetacean sighting records from 375 sighting survey in the Tsugaru Strait for ten years were compiled and the seasonal variability and yearly trend of cetacean encounter was examined. A total of 1876 school 19065 individuals were observed, and at least 7 species are identified such as Pacific white-sided dolphin, Dall’s porpoise, Habour porpoise, Minke whale, Bottle nosed dolphin, Common dolphin, and Killer whale. Except for Killer whale, the encounter of all of the cetacean were peaked during April to June. The encounter is rare during August and October, and no encounter has been recorded for this season for 10 years except for Pacific white-sided dolphin and Habour porpoise. The encounter rate of Harbour porpoise has been significantly increased. No encounter of Common dolphin and Bottle-nosed dolphin has been recorded after 2004, and the encounter to Killer whales had been occurred after 2009.
