Results of the Japanese dedicated cetacean sighting survey in the western North Pacific in autumn and winter season 2020/21
KOJI MATSUOKA, TAIKI KATSUMATA, ISAMU YOSHIMURA, FUTOSHI YAMAGUCHI, RIKI OHMUKAI, KENJI KONISHI, MEGUMI TAKAHASHI AND TAKASHI HAKAMADA
A systematic large-scale vessel-based sighting survey was conducted in 2020 and 2021 by Japan to examine the distribution and abundance of large whales in the western North Pacific. In this year, the survey was conducted in autumn and winter seasons, which information was very poor so far. The research area was set between 25oN-42oN and 140oE-150oE. The survey was conducted between 9 October and 19 November, 2020 in the autumn season, and between 26 January and 26 March, 2021 in the winter season. The research vessels Yushin-Maru No1, Yushin-Maru No.3 and Kaiyo-Maru No.7 were engaged in the surveys. A total of 4,484 n.miles was searched by the passing mode in the whole research area. Coverage of the searching efforts of the planned cruise track line was 93% for autumn and 71% for winter survey. In total, seven large whale species including fin (20 school /30 individual), sei (26/29), Bryde?s (29/33), common minke (1/1), North Pacific right (1 /1), humpback (54/80) and sperm (100/300) whales were sighted during whole research. Sei (25/28) and fin (15/25) whales were the most frequently sighted baleen whale species in the autumn and winter seasons, respectively. Distribution of large whales in autumn and winter seasons, for which there has been no systematic sighting survey for decades, was found. Especially, it was a new finding that fin whales were distributed in the eastern Hokkaido and Sanriku waters in winter season.