Geographical diet variations of Antarctic toothfish (Dissostichus mawsoni) in Area 88 of CCAMLR

The dietary compositions of Antarctic toothfish, Dissostichus mawsoni from various research blocks in Area 88 were analyzed for three years from 2019 to 2022 using metabarcoding. As a result of metabarcoding with 1,348 stomach contents, a total of 158 prey haplotypes were obtained which belonged to 33 families and 58 genera. As shown from the previous study conducted from 2016 to 2021, the main prey organisms of D. mawsoni were fish, in which Macrourus caml and Chionobathyscus dewitti were among the most abundant and frequently identified preys. As a result of clustering analysis, the dietary compositions could be divided into two clades according to the caught depth (slope/shelf). The proportions of three fish species, including Macrourus caml, Chionobathyscus dewitti, and Macrourus whitsoni were significantly high in the stomach of D. mawsoni, which were caught in deeper waters (slope clade), while highly variable prey compostions were identified in the shelf clade. DistLM analysis showed that total length, the caught water depth, and geographical difference significantly contributed to difference in prey compositions of Antarctic toothfish. Collectively, the dietary compositions of Antarctic toothfish clearly reflect the fish assemblages of the ocean for their fishery, suggesting that a long-term monitoring through metabarcoding will provide essential information for understanding ecosystem changes caused by catch of Antarctic toothfish.