This study has used bootstrap methodology to quantify the uncertainty in toothfish biomass estimates from Chapman mark-recapture and the CPUE-by-seabed area methods in Research Blocks in Subareas 58.4 and 48.6. The Chapman mark-recapture point estimates and their confidence intervals were generally much larger than the point estimates and confidence intervals from the CPUE-by-seabed area biomass estimates.
For Patagonian toothfish in Subarea 58.4 the confidence intervals of both methods overlapped in most years, providing some confidence in the estimates from the two different methods. The large differences in Antarctic toothfish biomass estimates using the two different methods suggests that the underlying assumptions currently made in one or both of the methods are likely to be invalid.
We recommend that Working Group consider reviewing assumptions in the CPUE-by-seabed area and the Chapman biomass estimation methods at the Research Block scale and prioritise resolving issues in Research Blocks that show the largest discrepancies.