Summary of the dedicated sighting survey under the Japanese Abundance and Stock structure Surveys in the Antarctic (JASS-A) in four austral summer seasons (2019/20–2022/23)

This document outlines the results of the first to fourth (2019/2020–2022/2023) dedicated sighting surveys under the Japanese Abundance and Stock structure Surveys in the Antarctic (JASS-A program). The main research objectives of JASS-A are i) the study of the abundance and abundance trends of large whale species, and ii) the study of the distribution, movement and stock structure of large whale species. The survey in the 2019/2020 to 2022/2023 austral summer seasons covered the sector 000°–035°E and 145°W–120°W, south of 60°S. A total of 6,694.2 n.miles was searched by the Normal Passing mode (NSP) and Independent Observer mode (IO). Four baleen whale species, Antarctic blue, fin, Antarctic minke, humpback, and four toothed whale species were sighted in the research area. Distance and angle estimation experiments for corrections of reported values by observers, were conducted. Experiments (photo-ID, biopsy sampling, and satellite tagging on large whales) as well as oceanographic and debris observations, were also conducted. The obtained sighting data will be used to estimate abundance and abundance trend of large whales. These estimates are required for the estimation of krill consumption by whales in the Indian and Pacific sectors of the Antarctic, which are in the interest to WG-EMM.