A preliminary assessment of mackerel icefish (Champsocephalus gunnari) in Division 58.5.2, based on recent survey results

The annual Random Stratified Trawl Survey was undertaken in Division 58.5.2 in the vicinity of Heard Island during April-May 2011. This paper provides a preliminary assessment of mackerel icefish population structure, abundance and yield for the area of Division 58.5.2 to the west of 79^o 20’ E using standard CCAMLR methods. A pattern of 5 year classes being present simultaneously in the population, which was first detected in 2011, has persisted, however a large cohort of fish, estimated to be 2+, dominate the population in both abundance and biomass. A new length weight model is estimated which indicates fish in the 2012 survey were heavier on average than predicted by the previous length weight model. Sensitivity testing indicates that the approach of using the lower 95th percentile of the biomass estimate effectively accounts for uncertainty in growth and mortality, relative to scenarios using the mean biomass estimate. A catch limit of 679 t is recommended for the 2012/13 season.