Preliminary results from the acoustic surveys of Antarctic krill conducted by the Chinese fishing vessel in Subarea 48.1 during austral summer 2025

Since the 2012/13 fishing season, the Chinese krill fishing vessels have been conducting annual krill acoustic survey in Subarea 48.1. During the 2024/25 fishing season, the survey was conducted by the Chinese krill fishing vessel Long Fa from 16 to 29 January 2025, covering the five core candidate management units including SSIW, BS, GS, JOIN and EI strata. During the field survey, krill biological sampling was also carried out at 81 stations using RMT8 net and CTD vertical profile sampling was deployed at 138 stations. The acoustic data were processed aboard by the scientific observer using automated processing technique (RapidKrill). Preliminary analysis suggested that concentrations of high density krill swarms were more frequently observed in the shelf regions to the east and south of the Elephant Islands and in the coast waters of the Gerlache Strait. The mean NASC for the entire survey area was estimated to be 123.36 m² n. mile^-2 (CV = 8.98%). Smaller krill with mean length less than 36 mm were generally found at stations in the shelf regions in the Bransfield Strait, Gerlache Strait and in waters close to the Joinville Islands. Preliminary results from the CTD data analysis were also presented, which suggested that the Antarctic Costal Current along the western Weddell Sea coast entering the Bransfield Strait may play the crucial role on the physical environment within the BS and be the main source of krill flux input to the BS.