Over 25,000 fish caught in the Australian toothfish and icefish fisheries around Heard Island and McDonald Islands on the Kerguelen Plateau have been aged from sectioned otoliths in the Australian ageing program since 1999, comprising more than 45,000 individual reads from seven different readers. The majority of fish aged are Patagonian toothfish, Dissostichus eleginoides (n = 23,770), however the age structure of a number of bycatch species, including grey rockcod, Lepidonotothen squamifrons (n = 1011), unicorn icefish, Channichthys rhinoceratus (n = 397), and grenadiers, Macrourus caml (n = 346) and M. carinatus (n = 300), have also been examined. The resulting age data are used in stock assessments for target and key bycatch species, as well as in investigations of age-related biological and ecological characteristics that are important in understanding the fish dynamics across the Kerguelen Plateau. We also present spatial distribution (actual and modelled) of D. eleginoides ages on the plateau.