The biomass of Antarctic toothfish (Dissostichus mawsoni) in CCAMLR Subarea 48.4 is estimated from tagging returns, giving an average of 1,456 tonnes since 2016. Applying the CCAMLR agreed precautionary assumption of average biomass, using the 5-year average biomass, and harvest rate of γ = 0.038, implies a 2020/21 yield of 55 tonnes.
Historically, a precautionary approach has been applied in treating 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.