Water Flow Requirements of Post-smolt Atlantic Salmon (Salmo salar L.) Reared in Intensive Seawater Flow-through Systems: A Physiological Perspective

Environmental challenges related to open sea cage production of Atlantic salmon have sparked interest in developing commercial-scale semi-closed systems for post-smolt (100–1000 g). Determining the mass-specific water flow required by post-smolts will largely influence design and dimensioning such systems. In this experiment, were exposed four levels specific flow: 0.2, 0.3, 0.4, 0.5 L kg fish−1 min−1. All treatments involved flow-through seawater with full oxygenation, a salinity 34‰, mean temperature 9.3 °C. The stocking density was kept stable at 75 m−3. Water pH decreased reduced flow, while partial pressure carbon dioxide (pCO2) total ammonia nitrogen (TAN) increased. increase CO2 reflected blood increased pCO2, HCO3−, Cl− lowest treatment (0.2 min−1), indicating typical regulatory response over eight-week experimental period. No negative effects on osmoregulation, external macroscopic welfare, or performance indicators observed, suggesting that within time period can compensate reductions down 0.2 However, avoid activating exhausting potentially energy-costly physiological mechanisms, it is suggested keep above 0.3 min−1 large-scale operations intermediate temperatures.