The 2019 stock assessment for Antarctic toothfish in the Ross Sea region estimated the precautionary yield using the CCAMLR decision rules and by applying the total catch limit of 3140 t between north of 70° S (19%), south of 70° S (66%), and the Special Research Zone (15%) in accordance with conservation measure 91-05 (2016) and 41-09 (2019). That stock assessment excluded data for vessels that had been previously quarantined by the Scientific Committee of CCAMLR due to data accuracy concerns. However, after the stock assessment had been completed, the Scientific Committee recommended that data from three additional vessels (Calipso, Koreiz and Simeiz 2015-2018) be quarantined pending an assessment of the implication of catch revisions from those vessels on the management advice.
Based on an analysis by Ukraine in 2020 the total DCD reported greenweight was 203 t greater than the reported C2 greenweight (12%) across Subareas 88.1, 88.2, and 48.2 from 2014–2018 for the three vessels combined. In the Ross Sea region, the difference totalled 78 t in 2014–2018 with the greatest difference occurring in 2018 (52 t).
A sensitivity model was run using the 2019 stock assessment incorporating the DCD estimated greenweight from the three vessels to revise the catch history in the assessment model. Both the MPD and MCMC estimates of initial biomass (B0) and current biomass for models with revised catch for the three vessels in trips between 2014 and 2018 were almost identical to the 2019 base case assessment model. Therefore, the differences for these trips resulted in a negligible impact on the estimated precautionary yield. We recommend that the Scientific Committee does not need to revise its 2019 advice for the toothfish catch limit for the 2020/21 season for the Ross Sea region.