Using tagging data to estimate Patagonian toothfish (Dissostichus eleginoides) biomass at Heard Island and McDonald Islands (HIMI) in Division 58.5.2 using the Chapman estimator

Within CCAMLR, the Chapman estimator is the agreed mark-recapture model in integrated assessment models used to estimate biomass from toothfish tagging studies.  However, recent discussions in CCAMLR working groups have queried the role that spatial and temporal heterogeneity of fishing and tagging effort might have on mark-recapture estimates.  As recommended by WG-SAM-2024 (para. 5.10), this paper presents externally estimated biomass time series that pertain to two different core areas as well as smaller areas within the HIMI EEZ.  These estimates are intended to serve as input data for sensitivities of the 2024 Patagonian toothfish stock assessment in Division 58.5.2.