Diet composition and feeding strategy of Antarctic toothfish, Dissostichus mawsoni in Subareas 88.1 and 88.3 in the 2022/23 fishing season

Investigations into the diet composition and feeding strategies of Dissostichus mawsoni in Subareas 88.1 and 88.3 were conducted based on stomach content analysis of specimens collected during the 2022/23 fishing season. In Subarea 88.1, 249 specimens (ranging from 70 to 190 cm in total length) were examined. D. mawsoni, a carnivorous and piscivorous species, primarily consumed fishes from the Macrouridae family, including Macrourus caml, M. whitsoni, and M. spp. Chionobathyscus dewitti of Channichthyidae were the second largest dietary component in the fish diet of D. mawsoni.  Mollusks were another important prey item, with small quantities of stones and echinoderms also present. For specimens larger than 100 cm, fishes (Macrouridae) dominated the diet. Graphical representations of feeding strategies revealed that D. mawsoni is an opportunistic and specialized predator on fishes (Macrouridae), showing a narrow niche width. The calculated trophic level for D. mawsoni was 4.25. In Subarea 88.3, 255 specimens (ranging from 53 to 188 cm in total length) were analyzed. Similar to Subarea 88.1, D. mawsoni in Subarea 88.3 primarily consumed fishes, with C. dewitti (Channichthyidae) as the dominant taxon. The Macrouridae family, including M. caml, M. whitsoni, and M. spp., comprised the second-largest dietary component. Mollusks, stones, crustaceans, and polychaetes were also part of their diet. In Subarea 88.3, fishes (Channichthyidae) were the dominant prey item across all size classes. The graphical representation of feeding strategies indicated that D. mawsoni is an opportunistic and specialized predator on fishes (Channichthyidae), showing a narrow niche width. The calculated trophic level for D. mawsoni in Subarea 88.3 was 4.26.