Morphological dietary composition of Antarctic toothfish (Dissostichus mawsoni) along the East Antarctic continental slope

To predict how the fishing of Antarctic toothfish, Dissostichus mawsoni, would affect the ecosystem, it is necessary to understand the species' ecological niche. Morphological analysis of the stomach contents of 960 D. mawsoni specimens collected at depths of 946-1600 m along the East Antarctic continental slope from December 2016 to March 2017 was used to assess dietary composition according to depth, sex, site, and size. Fishes were the most common prey item for D. mawsoni, comprising 97.8% based on the index of relative importance. Among the nine fish families consumed by D. mawsoni, Macrouridae was the dominant taxon. The size of D. mawsoni increased with depth. The dietary composition of D. mawsoni did not show significant differences by depth or sex, but did differ with site and size. D. mawsoni was the top predator in the ecosystem along the East Antarctic continental slope and can be considered an opportunistic feeder, feeding on abundant food in the environment. Therefore, additional studies of the diet of Antarctic toothfish are necessary to maintain the ecosystem structure and function in a changing environment, and the results of this study can be used as a monitoring baseline.