Results of the Japanese Abundance and Stock structure Survey in the Antarctic (JASS-A) during the 2020/21 austral summer season
Tatsuya Isoda, Taiki Katsumata, Masahiro Yamazaki, Nobuo Abe and Koji Matsuoka
The results of the second survey of the Japanese Abundance and Stock structure Surveys in the Antarctic (JASS-A) are reported. A dedicated sighting vessel (SV) was engaged in the survey based on the line transect method for 28 days, from 10 January to 6 February 2021 in the eastern part of Area IIIW (015?E?035?E). The survey design was based on IWC/IDCR-SOWER survey procedures and two survey modes were used, Normal Passing mode (NSP) and Independent Observer mode (IO). The total searching distance in the research area was 1,744.3n.miles (3,230.4km), including 887.3n.miles covered in NSP mode and 857.0n.miles in IO mode. The survey coverage was 68% in the northern stratum and 90% in the southern stratum. Four baleen whale species, Antarctic blue (24 schools/29 individuals), fin (136/228), Antarctic minke (51/120), humpback (359/697) and at least three toothed whale species, sperm (6/6), southern bottlenose (6/16) and killer (4/13) whales, were sighted in the research area. Antarctic blue whales were most sighted in the southern stratum of the research area. Fin whales were found mainly in the northern stratum. Antarctic minke whales were mainly distributed near the ice edge. Humpback whales were the most frequently sighted whale species, and widely distributed in the research area. Estimated Angle and Distance Experiments were completed in the research area. Routine photo-ID and biopsy sampling on large whales were also conducted during the whole survey (including transit), and a total of 62 photo-IDs (20 Antarctic blue, 41 humpback and one killer whales), were obtained. A total of 54 biopsy (skin and blubber) samples were also collected from eight Antarctic blue, 15 fin, 14 Antarctic minke, 16 humpback and one Bryde?s whales (in the transit area) using the Larsen system. Seven and ten satellite tags were deployed on fin and Antarctic minke whales, respectively. Time-Depth Recorders (TDR) tags were deployed on two humpback whales. Oceanographic observation was conducted at 99 stations using the eXpendable Conductivity, Temperature and Depth (XCTD). No marine debris were observed in the research area. Data and samples collected in this survey will be analyzed in conjunction with data and samples obtained during past research programs in the Antarctic (JARPA, JARPAII, NEWREP-A), in the context of the primary and secondary objectives of the JASS-A.