Performance of Atlantic salmon post-smolts reared in RAS with nanofiltered sulfate-reduced brackish water

Résumé fourni par la source

Hydrogen sulfide (H 2 S) accumulation in brackish water Recirculating Aquaculture Systems (RAS) poses a significant risk to the commercial production of Atlantic salmon ( Salmo salar ) due to potential mortality events. Nanofiltration to remove sulfate has been proposed to mitigate H 2 S formation risk, but the technology has an impact on water ionic composition and its consequences in fish physiology remain unexplored. This study examined the performance of Atlantic salmon post-smolts (72.6 ± 8.8 g) reared in nanofiltered sulfate-reduced brackish water (S- BW) at 15 PSU over four months, monitoring growth, gene expression of growth related genes, blood biochemistry, stress responses and bone health. Fish reared in normal brackish water (S+ BW) served as controls. Results showed no significant difference in overall fish growth (weight: 378 ± 75.0 vs 386 ± 70.6 g; length: 30.6 ± 2.1 vs 30.8 ± 1.8 cm; condition factor: 1.30 ± 0.11 vs 1.31 ± 0.10 g cm −3 ) between treatments after four months. Both divalent and monovalent plasma ion concentrations were consistently lower in the blood of the S- BW reared fish. Reduced stress response, indicated by lower water cortisol levels after transfer, suggests S- BW may provide a smoother transition environment. Vertebrae analyses indicated a potential risk of decreased stiffness and increased hyperradiodense malformation frequency in S- BW reared fish. Both stiffness reduction and hyperradiodense malformation may be reversible under appropriate environmental conditions. Therefore, further study beyond the observed four-month period is necessary to apply this technology for longer periods.

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