Identifying the optimal granularity level of traceable units is necessary when Implementing traceability of food This study examines granularity in a farmed salmon supply chain through the qualitative methods interview, observation, and document analysis The results show that fish feed and farmed salmon can have fine or coarse granularity of the batches Fine granularity will give large numbers and smaller batch sizes Coarse granularity will give fewer numbers and bigger batch sizes The granularity correlates to different levels depending on the application of information within a company and between companies in supply chains. (C) 2010 Elsevier Ltd All rights reserved.