Stress Evaluation Using Physiological Biomarkers on Fish Tested in the Hydraulic Facility

Understanding fish’s swimming ability is crucial for assessing their fitness and survival, impacting behaviors, including breeding, interactions between predators and prey, dispersal, and habitat choice. Fatigue curves are commonly used to describe swimming performance, neglecting physiological markers of stress level. This study aims to investigate the use of physiological data to deepen our comprehension of fish swimming performance. Experiments were conducted using a portable flume system in which fish were exposed to two different mean flow velocities (35 and 45 cm/s) until fish stopped swimming or at lower velocities to a maximum exposure time of 1800s. Levels of cortisol, the major stress hormone in fish, and the oxidative damage of lipids and proteins were measured in the muscle tissue of the experimental animals. Fish showed tendential lower stress levels (oxidative stress and cortisol responses) at higher water velocities than lower ones. One biochemical parameter increasingly associated with the metabolic activity is lactate, produced when glucose is consumed under anaerobiosis. In the experiments, lactate levels did not differ between low and high velocities, suggesting that there was no significant difference in the level of physical activity between the fish exposed to low and high water velocities in the flume system. Our article highlights the challenges of studying fish in the wild due to individual variability. Still, it emphasizes the importance of a more comprehensive understanding of fish behavior and physiology in natural environments. Studying fish in the wild is necessary for developing effective management strategies to promote their health and sustainability.