The local biomass of Antarctic toothfish (Dissostichus mawsoni) in CCAMLR Subarea 48.4 is estimated from tagging returns, giving a five-year average of 846 tonnes. Applying the CCAMLR agreed harvest rate of 3.8 % results in a 2025/26 catch limit of 32 tonnes. We recommend that this is used to set the catch limit for the 2025/26 season.
Following the recommendation of WG-FSA-IMAF-2024, we developed a length-based Casal2 model to determine an appropriate harvest rate for this stock which is consistent with the CCAMLR Decision Rules. We implemented constant catch scenarios to explore various harvest rates ranging from the current 3.8 % up to 15 % and projected forward for 35 years. Applying an analogue of the reference point of the CCAMLR Decision Rules in maintaining vulnerable biomass at 50 % of the initial estimate would result in a much higher harvest rate of 12 – 15 %, compared to the current 3.8 %.
Given that the parameters in the Casal2 model were largely borrowed and may not reflect the unique dynamics in Subarea 48.4, we do not propose to move away from the harvest rate of 3.8 % at this time, but welcome feedback on developing approaches to managing fisheries which form part of a larger stock.