Diet composition and feeding strategy of Antarctic toothfish, Dissostichus mawsoni in the area 88 for the exploratory longline fishery in 2024 of Korea

The stocks of Antarctic toothfish, Dissostichus mawsoni were a relatively economically and ecologically important fishery resource in the waters of Antarctic. However, there is not enough data and information to assess the robust stocks and deliberate proper measurements for sustainable utilize, especially relate to diet and feeding strategy which may lead to think about ecosystem based stock assessments and fishery managements. Therefore, the Korean scientists analyze diet composition and feeding strategy of D. mawsoni in the area 88 (subarea 88.1, SSRUs 88.2A and B, subarea 88.3) as a part of Korean research plan for the exploratory longline fishery for Dissostichus spp. during 2024 season. This study was carried out based on the results of stomach content identification of the D. mawsoni caught in the subarea 88.1, SSRUs 88.2A and B in CCAMLR conversion area from December 2023. The diet composition and feeding strategy of D. mawsoni were studied using 250 specimens (from 72 to 181 cm in total length) in the subarea 88.1, SSRUs 88.2A and B. D. mawsoni is a carnivore and piscivorous fish that mainly consumed fishes. Macrourus caml, M. whitsoni, and M. spp. of Macrouridae was dominant taxa. Chionobathyscus dewitti of Channichthyidae were the second largest dietary component in the fish diet of D. mawsoni. Mollusks were the second important prey item for D. mawsoni. Its diet also included small quantities of crustaceans and stones. In this study, fishes (Macrouridae) were the dominant prey item in all size classes except ≥160 cm. The graphical method for feeding strategy revealed that D. mawsoni is an opportunistic and specialized predator on fishes and showed narrow niche width. Calculated trophic level was 4.25 for D. mawsoni. Also, this study was carried out based on the results of stomach content identification of the D. mawsoni caught in the subarea 88.3 in CCAMLR conversion area from February to April 2024. The diet composition and feeding strategy of D. mawsoni were studied using 311 specimens (from 54 to 178 cm in total length) in the subarea 88.3. D. mawsoni is a carnivore and piscivorous fish that mainly consumed fishes. C. dewitti and Chionodraco spp. of Channichthyidae was dominant taxa. Lepidonotothen squamifrons, D. mawsoni, and Unidentified Nototheniidae of Nototheniidae were the second largest dietary component in the fish diet of D. mawsoni. Mollusks were the second important prey item for D. mawsoni. Its diet also included small quantities of crustaceans. In this study, fishes (Channichthyidae) were the dominant prey item in all size classes. The graphical method for feeding strategy revealed that D. mawsoni is an opportunistic and specialized predator on fishes (Channichthyidae) and showed narrow niche width. Calculated trophic level was 4.26 for D. mawsoni.