Consequences of continuous ozonation on the health and welfare of Atlantic salmon post-smolts in a brackish water recirculating aquaculture system.

Carlo C Lazado,Britt-Kristin Megård Reiten,Jelena Kolarevic,Kevin T Stiller,João Osório,Lill-Heidi Johansen

doi:10.1016/j.aquatox.2021.105935

Carlo C Lazado, Britt-Kristin Megård Reiten + Show 4 more

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https://doi.org/10.1016/j.aquatox.2021.105935

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Abstract

This study investigated the biological consequences of 45-day continuous ozonation on Atlantic salmon (Salmo salar) post-smolts in a brackish water recirculating aquaculture system (RAS). There was no significant difference in survival, operational welfare indicators, and average weight at termination between the ozone-treated and control groups. Plasma biochemical analyses revealed that the creatinine level was significantly higher in the ozone-treated group than in the control at termination. Histological evaluation of skin health showed no significant difference between the two groups. On the other hand, quantitative histopathology disclosed that the ozone group exhibited a better gill health status than did the control group, particularly at the end of the trial. Mucosal transcriptomics revealed a distinct response profile between the gills and skin. At day 45, there were no differentially expressed genes (DEG) identified in the skin, in contrast to 242 ozone-induced DEGs in the gills. Assessment of the transcriptomic profiles over time revealed that temporal effects were of greater impact in skin compared to gills, regardless of the treatment. The treatment did not result in metabolomic dysregulation and the overall profile lent support to the transcriptomics data that temporal effects had a greater influence on the changes observed. Exposure to handling-confinement stress revealed that ozone treatment did not alter the ability of post-smolts to respond to a secondary stressor. In summary, the suite of health and welfare indicators collectively indicated that continuous ozonation resulted in minimal physiological perturbations in salmon post-smolts. The results are expected to contribute to optimising the rearing conditions for post-smolts in RAS.

Highlights

Recirculation technology is becoming more and more common in fish farming
Recirculation aquaculture system (RAS) is essentially a Closed-containment systems (CCS) with fish tanks, filtration system and water treatment incorporated into one production loop
There was a significant temporal difference observed in the skin dam ages on the right sides of the fish (P = 0.013), especially in the ozone group (P = 0.020) (Fig. 1a); such trend was not observed on the left side of the fish

Summary

Introduction

Recirculation technology is becoming more and more common in fish farming. A case in point is Atlantic salmon (Salmo salar) aquacul ture, where technological innovations in closed systems highlight the advances of recent years (Lazado and Good, 2021). Closed-containment systems (CCS) are aquaculture systems that are separated from the surrounding ecosystem by an impermeable or semi-permeable wall. Recirculation aquaculture system (RAS) is essentially a CCS with fish tanks, filtration system and water treatment incorporated into one production loop. RAS is projected to contribute to improving farming sus tainability, as these systems ensure site flexibility, reduced water usage, lower effluent volumes, and better environmental control (Gonçalves and Gagnon, 2011). Since water is one of the fundamental resource in puts, the system must be equipped with an efficient strategy for its treatment and re-use

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