The analysis of the chemical composition of the shells of the Japanese clam is an effective tool to identify its geographic origin and, thus, combat fraudulent labelling and the illegal harvesting of hundreds of tonnes every year. The study is authored by Ricardo Calado, Andreia Santos, Fernando Ricardo, Renato Mamede and Seila Díaz, researchers from CESAM/DBIO and ECOMARE at the University of Aveiro (UA), and by Carla Patinha from the Department of Geosciences at UA. The technique is based on the so-called ‘elemental fingerprint’ of the shells, a natural chemical signature that reflects the environmental conditions in which the clams grew, and was developed at the University of Aveiro.
On Christmas Day 2025 alone, national authorities seized nearly five tonnes of live Japanese carpet shell clams at several locations across the country intended for human consumption. These clams are illegally harvested throughout the year in the Aveiro Lagoon, the Sado Estuary and, most notably, the Tagus Estuary, where they show high levels of metals, making their commercialization alive prohibited.
Ricardo Calado notes that “this level of contamination is so high and persistent that it becomes ‘imprinted’ in the shells of these clams as they grow in these locations, functioning as natural barcodes.” Even if the documentation is falsified, indicating that the clams originate from the Sado Estuary or the Aveiro Lagoon, “the elemental signatures of the shells unequivocally expose this fraudulent practice.”
The researcher adds that these natural codes cannot be falsified and that the team is already validating, in collaboration with national authorities, portable real-time screening solutions for live Japanese carpet shell clams harvested in the Tagus Estuary, so they can be removed from the market and thus safeguard public health, including that of foreign consumers, given that part of this product is exported to other European countries.
The study also revealed that it is possible to identify the harvesting season of the clams in around two thirds of the cases analysed, information that is particularly useful for frozen products marketed with shell.
The researchers state that this approach has great potential to strengthen seafood traceability, but stress that it is essential to maintain an updated reference database, with new samples collected every six to twelve months, to ensure the reliability of the models.
The team is also validating a technological package to transfer this solution to a major national food retail company, which aims to quickly and accurately confirm that the Japanese carpet shell clams it sells were not illegally harvested in the Tagus Estuary. At the same time, collaborations are underway with national and international authorities, including Europol, to develop solutions to combat illegal, unreported and unregulated fishing and other fraudulent practices that threaten public health and marine ecosystems.
Over the past ten years, the team has validated this approach for several species of bivalve molluscs, such as cockles, grooved carpet shell clams and Japanese carpet shell clams, but also for octopus, goose barnacles, sardines and even casulo, a live bait used in recreational fishing. Mineralised parts of the organisms, such as shells and scales, as well as soft tissues, were analysed.
Currently, the researchers are beginning to analyse processed foods and other food products, such as meat, vegetables and fruits, following requests from wholesalers and regulatory authorities in the food sector. They are also validating other technical solutions, including biochemical signatures and X-ray technology for faster elemental determination, supported by machine learning models that increase accuracy and automate the identification of product origin.
With the inauguration in June 2026 of CITAQUA-ECOMARE — the Aveiro Blue Hub Network pole led by the University of Aveiro, where the National Laboratory for the Traceability of Fisheries and Aquaculture Products will operate — the University of Aveiro will enter a new phase in the development and transfer of these technological solutions to authorities, wholesalers, retailers, fishers, shellfish harvesters and aquaculture producers. This laboratory will include a scientific equipment park unique in Europe, representing an investment of more than three million euros.
Original news in: UA News, 4 March 2026.