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 sea systems for post-smolt Atlantic salmon (100–1000 g). Determining the mass-specific water flow required by post-smolts will largely influence the design...
Published in: | Fishes |
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Main Authors: | , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
MDPI AG
2023
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Subjects: | |
Online Access: | https://doi.org/10.3390/fishes8060285 https://doaj.org/article/ee6379e33d864604b79af6a6bb233c18 |
Summary: | Environmental challenges related to open sea cage production of Atlantic salmon have sparked interest in developing commercial-scale semi-closed sea systems for post-smolt Atlantic salmon (100–1000 g). Determining the mass-specific water flow required by post-smolts will largely influence the design and dimensioning of such systems. In this experiment, post-smolts were exposed to four levels of specific water flow: 0.2, 0.3, 0.4, and 0.5 L kg fish −1 min −1 . All treatments involved flow-through seawater with full oxygenation, a salinity of 34‰, and a mean temperature of 9.3 °C. The stocking density was kept stable at 75 kg m −3 . Water pH decreased with reduced flow, while partial pressure of carbon dioxide ( p CO 2 ) and total ammonia nitrogen (TAN) in the water increased. The increase in water CO 2 was reflected in the blood with increased p CO 2 , HCO 3 − , and decreased Cl − in the lowest water flow treatment (0.2 L kg fish −1 min −1 ), indicating a typical regulatory response to increased water CO 2 over the eight-week experimental period. No negative effects on osmoregulation, external macroscopic welfare, or performance indicators were observed, suggesting that within the time period of this experiment, post-smolts can compensate for reductions in water flow down to 0.2 L kg fish −1 min −1 . However, to avoid activating and exhausting potentially energy-costly physiological regulatory mechanisms, it is suggested to keep specific water flow above 0.3 L kg fish −1 min −1 in large-scale operations with semi-closed sea systems at intermediate temperatures. |
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