SC/69B/ASI/05  

Document Number

SC/69B/ASI/05

Full Title

Cruise report of the 2023 IWC-Pacific Ocean Whale and Ecosystem Research (IWC-POWER)

Author

Hiroto Murase, Jessica Crance, Bernardo Alps, Isamu Yoshimura And Chikamasa Okoshi

Authors Summary

The 14th annual IWC-POWER cruise was successfully conducted between 28 July and 5 October 2023 in the eastern North Pacific (between 40ø00?N and US EEZ boundary, 180ø00?W and 155ø00?W, comprised entirely of the high seas). The cruise plan was endorsed at the SC/69A meeting. Researchers from the IWC, the U.S., and Japan participated. Survey trackline coverage in the research area was 84.6 %. Additionally, 172.80 n.miles were surveyed during transit between Japan to and from Dutch Harbor, and Dutch Harbor to and from the research area. During the entire the cruise, sightings of: North Pacific right (4 schools / 5 individual), blue (9/9), fin (116/193), sei (66/85), common minke (2/2), humpback (1/1), sperm (25/26) and killer (7/16) whales. Blue, fin and sei whales were mainly distributed in the northern part of the research area. Fin whales were the most frequently sighted large whale species. Photo-identification data were collected for: 4 right, 7 blue, 30 fin and 9 sei whales. A total of 19 biopsy (skin and sometimes blubber) samples were collected from 4 blue, 8 fin and 7 sei whales. A total of 146 sonobuoys were deployed, of which 143 were successful, for a total of over 538.28 monitoring hours. Species detected include sperm whales (107 buoys, 74.8%), fin whales (81, 56.6%), killer whales (53, 37.1%), blue whales (33, 23.1%), common dolphins (10, 6.9%), humpback whales (8, 5.6%), North Pacific right whales (7, 4.9%), Pacific white-sided dolphins (6, 4.2%), and sei whales (4, 2.8%). A total of 4 SPOT 177S tags were deployed on 4 blue whales. Five SPLASH-f-333 tags each were deployed on fin and sei whales. Two drifting buoy recorders (Long term Drifting Buoy Recorder, LT-DBR) were deployed during the cruise on behalf of Barlow, with an expectation that acoustic data of beaked whales could be recorded.

Publisher

IWC

Keywords

Publication Year

2024

Abstract

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 since 1978. The 14th annual IWC-POWER cruise was conducted between 28 July and 5 October 2023 in the eastern North Pacific (between 40ø00?N and US EEZ boundary, 180ø00?W and 155ø00?W, comprised entirely of the high seas). This area was surveyed in 2010 and 2011, but the survey was conducted from mid-July to mid-August while the 2023 survey will be conducted from mid-August to mid-September. The survey was conducted aboard the Japanese research vessel Yushin-Maru No. 2. The cruise was organized as a joint project between the IWC and Japan. The cruise plan was endorsed at the 69A IWC/Scientific Committee (IWC/SC) meeting. Researchers from the IWC, the U.S., and Japan participated in the survey. The cruise had four main objectives: (a) obtain information for the in-depth assessments of sei, humpback, gray and sperm whales in terms of abundance, distribution and stock structure; (b) obtain information on the critically endangered North Pacific right whale population in the Pacific; (c) obtain baseline information on distribution, stock structure and abundance for a poorly known area for several large whale species/populations, including those that were known to have been depleted in the past but whose status is unclear (e.g., blue and fin whales); (d) obtain essential information for the development of the medium-long term international programme in the North Pacific in order to meet the Commission?s long-term objectives.. At the pre-cruise meetings in Shiogama and Dutch Harbor, the crew 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. Survey trackline coverage in the research area was 84.6 % (1,476.57 n.miles of a planned distance of 1,745.00 n.miles), with a total of 742.29 n.miles in Passing with abeam closing mode (NSP) and 734.18 n.miles in Independent Observer passing mode (IO). Additionally, 172.80 n.miles were surveyed during transit between Japan to and from Dutch Harbor, and Dutch Harbor to and from the research area. During the entire the cruise, sightings of: North Pacific right (4 schools / 5 individual), blue (9/9), fin (116/193), sei (66/85), common minke (2/2), humpback (1/1), sperm (25/26) and killer (7/16) whales. Blue, fin and sei whales were mainly distributed in the northern part of the research area. Fin whales were the most frequently sighted large whale species. Photo-identification data were collected for: 4 right, 7 blue, 30 fin and 9 sei whales. These data are preliminary, pending further processing and photo-identification confirmation. A total of 19 biopsy (skin and sometimes blubber) samples were collected from 4 blue, 8 fin and 7 sei whales. The Estimated Angle and Distance Training Exercise and Experiment were completed. The acoustic survey was included for the 5th time to acoustically monitor for the presence of marine mammals, with particular importance for detecting and locating North Pacific right whales. A total of 146 sonobuoys were deployed, of which 143 were successful, for a total of over 538.28 monitoring hours. Species detected include sperm whales (107 buoys, 74.8%), fin whales (81, 56.6%), killer whales (53, 37.1%), blue whales (33, 23.1%), common dolphins (10, 6.9%), humpback whales (8, 5.6%), North Pacific right whales (7, 4.9%), Pacific white-sided dolphins (6, 4.2%), and sei whales (4, 2.8%). Other signals detected include northern right whale dolphins (2, 1.4%), Baird?s beaked whales (1, 0.7%), unidentified dolphins (2, 1.4%), and earthquakes (2, 1.4%). A total of 4 SPOT 177S tags were deployed on 4 blue whales. Five SPLASH-f-333 tags each were deployed on fin and sei whales. Two drifting buoy recorders (Long-term Drifting Buoy Recorder, LT-DBR) were deployed during the cruise on behalf of Barlow, with an expectation that acoustic data of beaked whales could be recorded. A seabird sighting survey was conducted as a feasibility study based on a proposal by Brownell. A total of 115 survey blocks along tracklines up to 15 minutes long was covered with sightings of 27 species of seabirds (466 individuals). This cruise was successfully completed and provided important information on cetacean distribution, in particular blue, fin and sei whales, in an area where limited survey effort had been conducted in recent decades, in a poorly known and logistically difficult area. These results will contribute to the aforementioned objectives of the IWC/SC.