Tag Data Processing for IOTC Tropical Tuna Assessments

IOTC maintains a database for the tagging data collected from the Indian Ocean Regional Tuna Tagging Programme, and the tag release/recapture observations have played a critical role in the stock assessments of the IO tropical tuna species. This report summarises how the tagging dataset were processed for incorporation into the recent Stock Synthesis assessments for yellowfin, bigeye, and skipjack tuna. The procedures and processes are very similar among the species/assessments (they generally included filtering of dubious records, correction for potential tag loss, and adjustment for under-reporting of recaptures), but there are some differences or inconsistency due to historical reasons (evolvement of individual assessments overtime, different researchers being involved in the analysis, etc). The report documents the assumptions and criteria being applied to ensure the reproducibility and transparency, and thus provides a basis for establishing a unified and consistent procedure for the processing of the tagging data for future assessments of IO tropical tuna species.