The biomass of Antarctic toothfish (Dissostichus mawsoni) in CCAMLR Subarea 48.4 is estimated from tagging returns, giving a geometric mean of 1,311 tonnes since 2016. Applying the CCAMLR agreed precautionary assumption of a 5-year geometric mean biomass, and harvest rate of γ = 0.038, implies a 2022 yield of 50 tonnes.
Historically, a precautionary approach has been applied in treating the 48.4 Antarctic toothfish as a separate stock. Based on the biological characteristics of the catches in Subarea 48.4, and the surrounding regions, the Antarctic toothfish around the southern South Sandwich Islands are now hypothesised as being part of a much larger stock that extends south into Subareas 48.2, 48.6 and possibly 48.5. The current method of assessment, based on tag returns, consequently, is considered to provide an estimate of the local biomass.
The assessment would lead to a recommendation from Working Group FSA to Scientific Committee that the catch limit for D. mawsoni in Subarea 48.4 should be set at 50 tonnes for 2021/22.