Preliminary study on the diet and feeding ecology of Macrouridae in Subareas 88.1 and 88.3

The stocks of Antarctic toothfish, Macrouridae 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 Macrouridae in the area 88 (subarea 88.1 and 88.3) as a part of Korean research plan for the exploratory longline fishery for Dissostichus spp. during 2025 season. Fish samples consisting of totally 300 (subarea 88.1: 100 and subarea 88.3: 200) Macrouridae were collected at various depths in each subarea (subarea 88.1: 637-1,580 m and subarea 88.3: 707-1,493 m)  by bottom longlines (trotline) using baited hooks with humboldt squid (Dosidicus gigas) and Pacific herring (Clupea pallasii) by Sun Star (subarea 88.1) and Green Star (subarea 88.3) fishing vessel in the area 88 from December 2024 to March 2025 (subarea 88.1: December 2024-January 2025 and subarea 88.3: February-March 2025). The diet composition and feeding strategy of Macrourus caml were studied using 90 specimens (from 18 to 32 cm in anal length) in the subarea 88.1. M. caml is a carnivore and crustacean feeder that mainly consumed crustaceans (mainly euphausiids). The graphical method for feeding strategy revealed M. caml is an opportunistic and specialized predator on crustaceans and showed narrow niche width. Calculated trophic level was 3.61 for M. caml. The diet composition and feeding strategy of M. whitsoni were studied using 10 specimens (from 21 to 24 cm in anal length) in the subarea 88.1. Among the 10 stomachs examined, 10 (100.0%) were empty. The diet composition and feeding strategy of M. caml were studied using 187 specimens (from 12 to 28 cm in anal length) in the subarea 88.3. M. caml is a carnivore and crustacean feeder that mainly consumed crustaceans (mainly euphausiids). The graphical method for feeding strategy revealed M. caml is an opportunistic and specialized predator on fishes and showed narrow niche width. Calculated trophic level was 3.88 for M. caml. The diet composition and feeding strategy of M. whitsoni were studied using one specimen (23 cm in anal length) in the subarea 88.3. The only stomach examined was empty (100.0%). The diet composition and feeding strategy of M. carinatus were studied using 12 specimens (from 19 to 26 cm in total length) in the subarea 88.3. M. carinatus is a carnivore and piscivorous fish that mainly consumed fishes. The graphical method for feeding strategy revealed that M. carinatus is an opportunistic and specialized predator on fishes, crustacean and showed narrow niche width. Calculated trophic level was 4.11 for M. carinatus.