Cruise report of multidisciplinary ecosystem survey in the eastern Indian sector of the Antarctic (CCAMLR Division 58.4.1) with a focus on Antarctic krill during 2018/19 season by the Japanese survey vessel, Kaiyo-maru

A multidisciplinary ecosystem survey in the eastern Indian sector of the Antarctic (CCAMLR Division 58.4.1) with a focus on Antarctic krill was carried out by Kaiyo-maru during the 2018/19 season for 53 days. The survey consisted of 2 survey periods: Leg 1 (from 15 December 2018 to January 2019; 24 days) and Leg 2 (from 26 January to 23 February 2019; 29 days). Leg 1 was commenced at ice edge on 80°E and ended at ice edge on 120°19.0’E. Leg 2 was commenced at 63°00.0’S on 150°00.0’E and ended at ice edge on 125°50.0’E. Two small scale oceanographic surveys (off the Mertz Glacier Tongue and the Totten Glacier) were also conducted during Leg 2. RMT tows were carried out at 72 stations (40 predetermined and 29 targeted stations with combination of both at 3 stations). SUIT tows were carried out at 28 stations. Quad NORPAC tows were carried out at 44 predetermined stations. Narrowband echosounder (38, 70, 120 and 200 kHz) data to estimate biomass of Antarctic krill were recorded along predetermined tracklines for 2,519 n.miles. Broadband echosounder data were recorded at 24 targeted RMT stations to estimate length distribution and swimming angles of Antarctic krill acoustically. The mass density and sound-speed contrasts against surrounding seawater of zooplanktons were measured 14 and 12 times, respectively. SADCP and PDR data were continuously recorded along the tracklines. A total of 101 CTD and 150 XCTD casts were made for physical and chemical oceanographic studies. Six types of autonomous profiling floats and buoys were deployed at 18 locations. Surface oceanographic environment data were continuously recorded along the tracklines. Sea ice (18 samples) and iceberg (15 samples) were collected for physical and chemical oceanographic studies. A total of 26 CTD casts were made for biological oceanographic studies. A total of 339 schools with 552 individuals of marine mammals were sighted during 1,249 n.miles of sighting effort along the tracklines. A total of 8,616 individuals of seabirds were sighted during 1,257 n.miles of sighting effort along the tracklines. Biological video recordings were made 25 times using 6 types of video recording devices. A number of analyses using obtained samples and data are in preparation and the results will be presented to the expert groups of SC-CAMLR.