Using an assemblage lens, this paper challenges this technical understanding by analysing how traceability affects and is affected by the relations that constitute global value chains. Analysing the introduction of the ThisFish traceability system in a small-scale tuna fishery in Indonesia we show how an NGO de-stabilised existing relations and expertise around landing and trading tuna and subsequently re-stabilised these relations in a different assemblage through the collection, collation and management of fisheries data.