Résumé
In this paper, we present a brief overview of the current work that has been undertaken for a fewyears to build the FIRMS Global Tuna Atlas (GTA) which requires compliant conversion factors forthe conversion of catch from numbers to weights. Indeed, the GTA aims to provide georeferenceddata of captures and efforts for tuna and tuna-like species. The actual dataset for catches containstwo units: Tons and Number of fish, with some data redundant because provided in both units.This dataset is not as workable as would be a dataset where units are harmonized. Thus, the nextstep will be to convert the data provided in number of fish to tons, with an accurate and validateddataset. This treatment is already done by IRD using a historical dataset but the resulting data willnot be validated by FIRMS without further confirmation on the treatment done. This paper aimsto inform about the necessity of a validated conversion factors dataset. It also aims to ask IOTCand, in a second step, other tRFMOs, for collaboration on this topic. We first discuss the currentconversion factors provided by tuna Regional Fisheries Management Organisations (e.g., IOTC) andby the French Institute of research for development (IRD). Eventually, we present a plan to validateconversion factors for scientific purposes.