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Document Number

SC/69B/ASI/04

Full Title

Results of the Japanese Abundance and Stock structure Survey in the Antarctic (JASS-A) during the 2023/2024 austral summer season

Author

Tatsuya Isoda, Takashi Yoshida, Isamu Yoshimura, Yujin Kim, Claudio A. Moraga, Eisei Ueta, Masanori Higashi, Kanae Kawajiri, Chikamasa Ohkoshi, Nobuo Abe And Koji Matsuoka

Authors Summary

The results of the fifth research cruise of the Japanese Abundance and Stock structure Surveys in the Antarctic (JASS-A) are reported. Two dedicated sighting vessels (SVs) were engaged in the survey based on the line transect method for 36 days, from 7 January to 11 February 2024 in Area IV-West (70øE?100øE). For the survey, the research area was divided into northern, southern strata and Prydz Bay strata. In addition, surveys were conducted in coastal ice-free waters in the Davis Sea. 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 3,278.3n.miles. Four baleen whale species, Antarctic blue (15 schools/18 individuals), fin (200/467), Antarctic minke (111/178), humpback (874/1,706) and at least two toothed whale species, sperm (42/43), and killer (19/263) whales, were sighted in the research area. Estimated Angle and Distance Experiments were completed. A total of 199 photo-IDs (16 blue, 94 humpback, 5 southern right and 84 killer whales) were obtained during the whole survey. A total of 54 biopsy samples were collected from 8 Antarctic blue, 9 fin, 3 Antarctic minke, 24 humpback, 4 southern right, 3 sei and 3 killer whales during the whole survey. In addition, oceanographic and marine debris data were collected. 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.

Publisher

IWC

Publication Year

2024

Abstract

The results of the fifth research cruise of the Japanese Abundance and Stock structure Surveys in the Antarctic (JASS-A) are reported. Two dedicated sighting vessels (SVs) were engaged in the survey based on the line transect method for 36 days, from 7 January to 11 February 2024 in Area IV-West (70øE?100øE). For the survey, the research area was divided into northern, southern strata and Prydz Bay strata. In addition, surveys were conducted in coastal ice-free waters in the Davis Sea. 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 3,278.3n.miles (6,071.4km), including 1,595.0n.miles covered in NSP mode and 1,683.3n.miles in IO mode. The survey coverage was 74% in the northern stratum, 93% in the southern stratum, 89% in the Prydz Bay, and 89% in coastal ice-free waters in the Davis Sea. Four baleen whale species, Antarctic blue (15 schools/18 individuals), fin (200/467), Antarctic minke (111/178), humpback (874/1,706) and at least two toothed whale species, sperm (42/43), and killer (19/263) whales, were sighted in the research area. Humpback whales were the most sighted whale species. This species was distributed in all research area except in the south part of coastal ice-free waters in the Davis Sea. Fin whales were the second most sighted species and were mainly distributed in the northern and southern strata. Antarctic minke whales were the third most sighted species and were mainly distributed in the southern part of the research area with higher concentrations observed in the southernmost part of coastal ice-free waters in the Davis Sea. Estimated Angle and Distance Experiments were completed. Routine photo-ID and biopsy sampling on large whales were also conducted during the whole survey (including transit). A total of 199 photo-IDs (16 blue, 94 humpback, 5 southern right and 84 killer whales) were obtained. A total of 54 biopsy samples were collected from 8 Antarctic blue, 9 fin, 3 Antarctic minke, 24 humpback, 4 southern right, 3 sei and 3 killer whales during the whole survey. Satellite tags were deployed on 6 fin, 2 Antarctic minke, and 3 humpback whales during the whole survey. Oceanographic observations were conducted at 148 casts using the eXpendable Conductivity, Temperature and Depth (XCTD). One marine debris was observed in the research area. The VTOL-UAV ASUKA conducted a successful autonomous flight for a total distance of 297.5n.miles, and collected aerial images related to whale sighting surveys. 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.

SC/69B/ASI/04

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