Validation and Application of Fecal Cortisol and Its Metabolites as a Stress Indicator in Farmed Atlantic Salmon (Salmo salar)

Abstract

In 2023, 62.8 million Norwegian salmon (16.7 percent) died during the sea phase, underscoring the significant welfare challenges faced by the industry. Poor fish welfare is closely linked to elevated stress, and monitoring stress levels could allow for early detection of issues, preventing them from worsening and affecting fish welfare. Traditional methods often rely on blood samples to measure stress reponses, which can harm the fish due to its invasive nature. My research aimed to develop an animal friendly material that could be used to accurately measure stress levels, while being easier to collect and applicable across various aquaculture settings.

In my Ph.D. work, I focused on using fecal samples to monitor stress levels in farmed salmon. By comparing cortisol levels in the blood, cortisol and its metabolites measured in feces were validated to accurately indicate stress levels in fish. They also offer a delayed and extended sampling window to measure stress responnses in farmed salmon, which is particularly helpful on commercial sea cages where immediate sampling can be difficult. Furthermore, fecal sampling can be easily performed in different aquaculture settings, making it a practical tool for farmers to conduct.

This Ph.D. work privde new insights of using feces as a matrix for measuring stress responses in farmed salmon. By this method, farmers can monitor fish health with less harm, fostering more sustainable and animal-friendly practices. As the aquaculture industry places greater emphasis on animal welfare and sustainability, this method has the potential to become an essential tool in fish farming.