Trace element fingerprinting of blue mussel (Mytilus edulis) shells and soft tissues successfully reveals harvesting locations.

Globally, aquaculture products are expected to account for >60% of total seafood produce by 2030. In the European Union, the seafood sector is of considerable economic importance to member states with household spending on seafood produce totalling €54.8 billion in 2016. Within the EU, shellfish aquaculture supports livelihoods and employment in many rural communities throughout the region. Harmful algal blooms pose considerable risk to consumer safety and in turn, stability of the shellfish market. If contaminated produce was to make it to the market the health risk to the public could be considerable, but the damage to the sector through loss of trust in producers would also be significant. Mytilus edulis account for a considerable portion of the aquaculture sector in the Northeast Atlantic. At present, no scientific tool is available to industry regulators, to allow them to trace mussel produce to its source, uphold food safety standards and ensure consumer confidence. The present study uses chemical analysis of shells and soft tissues to classify individual M. edulis to their site of harvest. The use of random forest classification of trace element composition has revealed location specific elemental signatures for all examined sites. This led to the correct classification of 100% of individuals sampled to their respective harvesting locations, including two sites located just 6 km apart within the same bay. The protocol demonstrated here provides the basis for a scientifically driven traceability framework for shellfish produce.