The so-called "Kobe Process", a series of informal joint meetings of the tuna Regional Fishery Management Organizations, has identified a number of issues that should be analyzed in order to improve harmonisation globally. The process identified harmonisation of bycatch data collected by the RFMOs as one such issue. This document is a report of a meeting of technical experts tuna longline fisheries, which provided the first opportunity for progress towards harmonisation of bycatch data for these fisheries. The objective of this meeting was to review the documentation of the data fields that are equivalent and those that are unique to particular RFMOs for the purpose of assisting with comparison across tuna RFMOs. The workshop findings should assist the Joint tuna RFMO Bycatch Technical Working Group with completing the data harmonisation aspects of its workplan.