Preliminary tag-recapture based population assessment of Antarctic toothfish in Subarea 48.4

The biomass of Antarctic toothfish (Dissostichus mawsoni) in CCAMLR Subarea 48.4 is estimated from tagging returns, giving a five-year average of 1,110 tonnes since 2018. Applying the CCAMLR agreed precautionary assumption of a 5-year average biomass, and harvest rate of γ = 0.038, implies a 2023 yield of 42 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.