Risk assessment for the Antarctic starry skate (Amblyraja georgiana) in the Ross Sea

The Scientific Committee identified skates as “priority bycatch taxa for which assessments of status are required”. Catch data from the Ross Sea region show that most (~90%) of the skate catch consists of Antarctic starry skate (Amblyraja georgiana) and that this species is the only one with enough mark-recapture data to estimate local biomass. We present updated biomass estimates and exploitation rates consistent with the CCAMLR decision rules for A. georgiana in the Ross Sea, providing a range of possibilities for biomass and exploitation estimates. Model uncertainties still exist, particularly around post-release mortality. Biomass and exploitation estimates were highly reliant on assumptions about mortality and recruitment steepness. Current exploitation was considered sustainable if initial release mortality is < 40% (where skates are cut off the line), irrespective of assumptions on tagging cohort treatment and across plausible extremes of natural mortality. We note that the following would reduce model uncertainties: (1) the planned year of skate tagging commencing in the 2027/28 season; 2) recording of skate injury condition at capture and release, and (3) research to improve post-release mortality estimates. We recommend Conservation Measure 41-01, Annex 41-01/C, paragraph 2(x) should remain as is to ensure skates are sampled.