We present an update of ageing and estimates of biological parameters, and of the integrated stock assessment for Antarctic toothfish (Dissostichus mawsoni) fishery in CCAMLR Divisions 58.4.1 and 58.4.2. The update of ageing and estimates of biological parameters addresses Milestone 1.10, the updated of the stock assessment addresses Milestone 1.11 of the current multi-member research plan for these Divisions (WG-SAM-2021/03).
The assessment model used all data available from the region, supplemented with parameter estimates from other toothfish stock assessments. Compared to the previous assessment (SC-CAMLR-39/BG/38), this model also included more tag-recapture data from Division 58.4.2, new ageing data from the 2020 and 2021 fishing seasons, and an update estimation of region-specific growth.
The evaluated assessment model indicated that the Antarctic toothfish stock in Divisions 58.4.1 and 58.4.2 is unlikely to be depleted by the current level of fishing mortality.
However, the model also clearly highlighted the impact of no fishing in Division 58.4.1 over the last four years. The lack of data from this Division is strongly impacting on the ability of the model to accurately estimate spawning biomass and precautionary catch levels for this exploratory toothfish fishery.
Research in Divisions 58.4.1 and 58.4.2 has now progressed to a stock assessment, highlighting the value of the management procedures with a requirement for a research plan in exploratory fisheries, as agreed to by CCAMLR in 2011. However, widespread data collection in both Divisions 58.4.1 and 58.4.2 is the single biggest need in this fishery to improve the stock assessment model and allow it to be used for management advice on catch limits in the future. We therefore strongly recommend that exploratory fishing under the new research plan resume in Division 58.4.1 such that tagging and data collection can occur beyond the current limited areas in Division 58.4.2.