The scientific research fishing was conducted by the vessels “Greenstar” (KOR) and “Marigolds” (UKR) in CCAMLR Subarea 88.3 following the survey design (WG-FSA-IMAF-2024-52 Rev. 1). The total catch of Dissostichus mawsoni was 114415.41kg comprising 5,125 individuals. The CPUE for D. mawsoni varied among the research blocks, and demonstrates moderate upside comparable to the previous season. CPUE demonstrated high variability in all research area with mean range of 100 to 384 kg/1000 hooks. The vessel calibration study was completed in research block 88.3_3, and 88.3_4. Also, random stations were set in new research blocks 883_11 and 883_12.
The tagging rate and tag overlap in Subarea 88.3 were 6.46 fish per ton and 94 % overlap for Greenstar, and 5.48 fish and 84.93% for Marigolds. Extra efforts were made in tagging in new research blocks.
To analyze length frequency of D. mawsoni, a total of 3380 individuals were measured through the season. In block 88.3_1 observed high proportion of juvenile specimens of Antarctic toothfish despite all catches were obtained deeper than 1200 m. In blocks 88.3_3, 88.3_4, 88.3_11, and 88.3_12, a bimodal distribution with medians 60 cm and 150 cm was observed. uvenile fishes were present in catches in all research blocks, even at greater depths. Similar length composition with various proportion of juvenile fishes is usually observed in research blocks of the Amundsen Sea.
The only mature fraction of the toothfish population was observed in block 88.3_3 this year with stage 3 ( “Developed”) gonads. More fish with immature gonads were observed in research block 88.3_3 and 88.3_4 then last year. Majority of the fish caught in the area of research had an “immature” or “developing” stage of gonads.
During the 2025 research season, Macrourrus caml was the main bycatch fish and important prey for Antarctic toothfish. Nearly 2% of identified Macrourids were identified as Macrourus whitsoni. Females of Macrourus caml were observed more often in catches, and they prevailed in length and weight over males. Off-water analysis of otoliths and whole collected specimens of Macrourids (200 specimens collected on Greenstar) will help to better understand biology and population structure of Macrourus caml in the area of research. Also, 262 pairs of otoliths of Macrouridae were collected for further identification by two vessels.