Cortisol Measurements
Cortisol is an important biomarker of stress response and fish welfare. Blood plasma is the established standard matrix for measuring cortisol. However, plasma cortisol primarily reflects the fish’s acute stress response at the time of handling and may therefore be influenced by stress occurring during the sampling process itself.
In contrast, cortisol accumulates in the mucus layer and feces over a longer time period (approximately one hour), providing a more integrated and representative measure of the fish’s underlying stress level. In addition to improving animal welfare—by avoiding pain, handling stress, and the need for euthanasia—swab sampling is non-invasive, operationally simpler, and can be carried out directly by site personnel. This enables more frequent and practical stress monitoring under commercial aquaculture conditions.
For these reasons, we use surface samples for cortisol analysis as a non-lethal and non- or minimally invasive alternative to blood sampling. Cortisol measurements constitute one of the core biomarkers in the Salmo Surveillance modules, a cutting-edge tool developed to support improved fish health management and fish welfare monitoring.
