Swimming in unsteady flows: Physiological assessments of salmonid exercise performance

As climate change and environmental pressures are becoming more eminent, fish farms are moving from the calm coastal waters to rougher open-ocean sites. These new locations have constantly changing water currents. To farm fish responsibly in offshore areas, we need to understand how the fish react to these shifting water flows so we can design better cages, choose good sites, and feed the fish properly. We also need reliable ways to track how active the fish are and how much energy they spent, so farmers can guard their health and welfare. We studied how Atlantic and Chinook salmon swim, how their heart rates change, and how their movement patterns shift in changing currents. We found that swimming in unsteady flow requires more energy for salmon. Their heart rates and movement patterns clearly showed when they had to working harder or were becoming stressed. We also found that training salmon in these changing currents improved their growth and feeding efficiency.