Summary of Antarctic toothfish tagging data through 2020 and projected recaptures in Subarea 88.3

The research plan on Antarctic toothfish in Subarea 88.3 has been underway for four consecutive years. Two vessels have participated in tagging and releasing toothfish from 8 discrete areas. Subsequent fishing effort has recaptured some fish, which can now be used to transition the research to a “biomass estimation” phase based on catch limits for each research block following CCAMLR’s trend analysis rules. A total of 2309 tagged fish have been released and 11 recaptured, all in research block 883_4. As proposed in the research plan milestones, we applied the observed recapture rates to the projected catch limits to set expectations of future recaptures using the trend analysis rules to evaluate the likelihood of achieving enough recaptures for stock assessment purposes. We estimate that, at least for research block 883_4, obtaining recaptures of more than 6 tags per year is feasible at the current tagging rate of 5 fish per ton of catch, but only if vessel performance is maintained and within-season recaptures do not occur.