The SensoFiA project, funded under grant 031B0915K2, ran from 1 December 2020 to 30 September 2023 and was led by Dennis Lohmann of Nordischer Maschinenbau Rudolf Baader GmbH & Co. KG (BAADER). Its goal was to develop a sensor system that can rapidly assess stress, welfare and product quality in fish rearing and processing operations. The scientific partner was the Fraunhofer Institute for Manufacturing Technology and Advanced Materials (Fraunhofer IMTE), formerly EMB, both located in Lübeck. A sister project, BioFiA, supplied the experimental data on stress markers that SensoFiA intended to translate into a field‑ready sensor.

The technical work focused on Atlantic salmon (Salmo salar) because this species is widely cultivated by BAADER’s customers. In the laboratory, Fraunhofer IMTE established primary cell cultures from brain, liver, head kidney and skin tissues, optimizing isolation and growth conditions for each organ. These cultures were used to screen a panel of mRNA markers reported in the literature as indicators of fish stress. Five stress‑related genes were consistently detected across the different cell types, and primer sets were validated against the Atlantic salmon genome to confirm species specificity. The next step was to move from tissue samples to a non‑invasive sampling method that could be applied in commercial settings. A patented technique from Fraunhofer was employed to isolate and stabilize mRNA directly from holding water. The stabilizer, however, is a toxic powder that cannot be used near edible fish, and the required –80 °C transport from Norway to Germany was not feasible. Consequently, a room‑temperature stabilizer was adopted, and laboratory tests confirmed that it preserved mRNA integrity under controlled conditions. Field samples collected during a single Norwegian trial, however, yielded RNA concentrations too low to reveal clear differences in stress‑gene expression between sampling points along the production chain. Variations in transport time, temperature fluctuations and higher salinity in the fjord water likely contributed to mRNA degradation. Despite the lack of definitive stress signatures in the water samples, the field visit provided valuable insight into the handling, pumping, crowding and stunning stages of salmon processing, allowing the team to identify the most stressful points in the workflow.

The project’s outcomes demonstrate that Atlantic salmon stress genes can be reliably detected in cultured cells and that a non‑invasive sampling approach is theoretically feasible, though practical challenges remain. The data generated will inform the design of a future sensor platform that could monitor stress markers in real time, enabling producers to adjust environmental parameters such as temperature, oxygen, pH, light and noise to maintain fish welfare and product quality. The knowledge gained about the production chain and the limitations of current sampling methods will guide the next phase of sensor development.

Collaboration-wise, BAADER provided industry expertise, access to commercial salmon farms, and facilitated contact with end users. Fraunhofer IMTE supplied the biological and molecular biology expertise, performed cell culture work, and developed the mRNA isolation protocol. The project was coordinated by BAADER’s project lead, with scientific oversight from Fraunhofer. The partnership was supported by German research funding, and the project’s progress was reported to the funding agency through a short report. The timeline was disrupted by the COVID‑19 pandemic, which forced the redesign of the BioFiA experimental plan and limited field access, resulting in only one Norwegian trial. Nonetheless, the collaboration produced a set of validated stress markers and highlighted the technical hurdles that must be overcome to bring a practical sensor system to market.