Results of the Japanese dedicated cetacean sighting survey in the western North Pacific in 2018
Koji Matsuoka, Takashi Hakamada, Isamu Yoshimura, Taiki Katsumata, Hedenori Kasai and Tomio Miyashita
A systematic large-scale vessel-based sighting survey was conducted in 2018 by Japan to examine the distribution and abundance of large whales in the western North Pacific. The research area was set between 35Â° N and 46Â° N and between 135Â° E and 150Â° E (sub-areas 11, 10E, 7CN and 7CS for common minke whale). The survey was conducted between 28 April and 27 May. The research vessels Yushin-Maru No.2 and Kaiyo-Maru No.7 were engaged. A total of 2,869.9 n.miles was searched by the passing mode in the research area. Coverage of the searching efforts of the planned cruise track line was 85% for sub-area 11, 87% for sub-area 10E, 90% for sub-area 7CN and 89% for sub-area 7CS. High-density areas of fin, common minke and humpback whales were observed in sub-areas 11, 10E and 7CS. Fin whales were sighted most frequently in the research area. In total, five large whale species including fin (61 schools / 110 individuals), sei (3), Brydeâ€™s (8/10), common minke (48/50), humpback (32/39) and sperm (7/13) whales were sighted during the cruise. Photo-ID images were collected from humpback (10 individuals) whales. Biopsy skin samples using a Larsen system were collected from fin (2), sei (2) and humpback (1) whales. The sighting data was submitted to the IWC secretary based on the SC guideline and will contribute to the work on management and conservation of large whales by the IWC SC.