Swimming in steady and unsteady flows: swimming performance, training effects and activity patterning in a sea cage

The quest to move mariculture from sheltered areas to exposed areas of the sea for future expansion to increase productivity is gaining prominence. The New Zealand government, for instance, has targeted a six-fold increase in aquaculture productivity by 2035 via mariculture in exposed seas (Plant & Food Research, 2020). This triggers the need to understand the swimming performance of cultured fish species and associated energy cost, under unsteady water flow conditions as experienced in offshore technology for finfish production. Most of the data available on fish swimming performance have been obtained on swimming sustainedly in uniform water flows under controlled conditions. But what if the flow is unsteady as often experienced under natural conditions? Researchers have studied swimming performance and its associated energy cost under steady flow conditions but to the best of our knowledge, no investigation has been made into the swimming performance of farmed Atlantic salmon (Salmo salar) under unsteady flow conditions and coupled with the use of acoustic accelerometer transmitters. These tags are being positioned as innovative tools for monitoring species-specific activity patterns in nature but also in aquaculture. In this study, we will use acoustic accelerometer transmitters to establish the correlation between metabolic rate and the overall dynamic body acceleration of farmed Atlantic salmon at various swimming speeds, at various temperatures and under both steady and unsteady flow conditions. For this purpose, we will execute controlled experiments in a Brett-type swim-flume and execute a long-term training trial under different flow regimes. Ultimately, the gained knowledge will be used for the interpretation of activity patterns and performance data of Chinook salmon (Oncorhynchus tshawytscha) under variable temperature and flow regimes in offshore production technology.