The assessment of toothfish in CCAMLR subarea 48.3 currently uses the first four years of tag recaptures post release as input data, whereas the assessment in subarea 48.4 uses all available recapture data (excluding in-year recaptures). A theoretical analysis of the use of data from double-tagged recaptures suggests that including recaptures from fish at liberty for long periods will introduce bias into the assessment. Sensitivity tests on both stocks show that this bias occurs in practice. Sensitivity tests on the 48.3 assessment show that this bias is not entirely explained by the effect of double tagging.
Dr Marta Söffker (European Union)
Ms Jane Rumble (United Kingdom)