Assessment of mackerel icefish (Champsocephalus gunnari) in Division 58.5.2 based on results from the 2020 random stratified trawl survey

The annual random stratified trawl survey was undertaken in Division 58.5.2 in the vicinity of Heard Island and McDonald Islands during April 2020. Based on data from this survey, this paper provides an assessment of mackerel icefish (Champsocephalus gunnari) population structure, abundance and yield in Division 58.5.2 to the west of 79o 20’ E using standard CCAMLR methods (CMIX and Generalized Yield Model). Additionally, recent work has been undertaken as part of the krill management strategy re-implementing the Generalized Yield Model software in R, and the two implementations resulted in highly consistent assessment results. The 2020 survey showed a large 2+ cohort in the population and a high biomass. Based on the Grym implementation, catches of 1276 t in the 2020/21 season and 1047 t in the 2021/22 season satisfy the CCAMLR decision rules.