Cruise report of the 2020 IWC-Pacific Ocean Whale and Ecosystem Research (IWC-POWER)
Hiroto Murase, Taiki Katsumata, Isamu Yoshimura, Soya Fujii, Nobuo Abe and Koji Matsuoka
IWC-POWER cruises in the North Pacific follow the series of IWC/IDCR-SOWER (Southern Ocean Whale and Ecosystem Research) cruises that were conducted in the Antarctic from 1978 to 2010. The 11th annual IWC-POWER cruise was conducted between 11 July and 24 September 2020 in the High-Sea of the Central North Pacific. The survey was conducted aboard the Japanese R/V Yushin-Maru No. 2. The cruise was organized as a joint project between the IWC and Japan. The cruise plan was endorsed at the 68B IWC/Scientific Committee (IWC/SC) meeting. Same as previous IWC-POWER cruises, the present cruise made a valuable contribution to the work of the IWC/SC on the management and conservation of populations of large whales in the North Pacific in a number of ways, including providing: (a) information for the ongoing assessments of North Pacific sei, humpback and gray whales in terms of abundance, distribution and stock structure; (b) information on endangered North Pacific right whales; (c) baseline information on distribution, stock structure and abundance for a poorly known area for other cetacean species/populations, including those that were known to have been depleted in the past but whose status is unclear; (d) essential information for the development of the medium-long term international programme in the North Pacific to meet the Commission?s long-term conservation and management objectives. In addition, a primary focus was to collect IO data to allow more robust estimation of g(0) for at least fin and sei whales as well as to provide comparable coverage of the western part of the southern stratum of the 2010 survey. Two international researchers from USA were initially nominated. However, they could not participate in the cruise because restrictions on travel from the USA to Japan was not lifted in advance of the survey due to COVID-19. At the pre- and mid-cruise meetings, the crews of the vessel and international researchers agreed on the procedures and objectives of this survey. The survey was conducted using methods based on the guidelines of the IWC/SC. Passing with abeam closing mode (NSP) and 961.0 n.miles in Independent Observer passing mode (IO). Additionally, 521.3 n.miles were surveyed during transit between Japan and the research area. During the entire cruise, sightings of: blue (22 schools / 31 individuals), fin (29/32), sei (131/181), Bryde?s (6/8), common minke (3/3), humpback (7/8), sperm (56/90) and killer (18/71) whales were observed. Blue whales were mainly distributed in the northern part of the research area to the west of 170?E. Sei whales were the most frequently sighted large whale species. North Pacific right whale was not sighted during the cruise. Photo-identification data were collected for: 26 blue, 3 humpback and 17 killer whales. These data are preliminary, pending further processing and photo-identification confirmation. A total of 65 biopsy (skin and sometimes blubber) samples were collected from 13 blue, 9 fin, 38 sei, 1 Bryde?s, 2 humpback and 2 killer whales. No acoustic survey was conducted in the cruise. The Estimated Angle and Distance Training Exercise and Experiment were completed. A total of 67 objects of marine debris were observed. This cruise was successfully completed and provided important information on cetacean distribution, in particular blue, fin and sei whales, in a poorly-known and logistically difficult area, where limited survey effort had been spent in recent decades. These results will contribute to the aforementioned objectives of the IWC/SC.