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HAVBRUK2-Stort program for havbruksforskning

Prevalence and consequences of hydrogen sulphide in land-based Atlantic salmon production

Alternative title: Omfang og konsekvenser av hydrogensulfid i landbasert lakseoppdrett

Awarded: NOK 12.0 mill.

Norwegian Atlantic salmon aquaculture has made some significant strides in technological innovations, especially in the development of closed and semi-closed rearing systems. This has resulted in the conservation of water and a greater ability to control the production environment. However, other challenges with these systems have presented themselves. Specifically, hydrogen sulphide (H2S) has become increasingly prevalent in Norwegian salmon recirculating aquaculture system (RAS) facilities, with several events of mass mortality in recent years. There is, however, a substantial gap in the current understanding concerning the biology and physiology of H2S-fish interactions, specifically in salmon. H2Salar is a timely and ambitious project that aims to create knowledge and advance our understanding of the risks and impacts of H2S to the physiology of Atlantic salmon in RAS. Instead of immediately developing solutions to combat the threat, the lack of fundamental knowledge prompts this initiative to adapt a process-based, research-driven approach that will identify the risks both under laboratory and field-based trials; elucidate underlying mechanisms involved in H2S-salmon interaction from molecular to organismal level; and provide a holistic documentation of the impacts to the different physiological systems that are key for fish health, welfare and robustness. It is expected that the results will be valuable across different sectors of the aquaculture industry that are affected by this issue and the challenges of land-based salmon production in general. A strategic project consortium has been assembled, including two of Norway's leading R&D institutes on the environmental and biological aspects of recirculation technology (Nofima, NIVA) and a top-rank academic institution with strong expertise in fish physiology (DTU). In addition, a Reference Group has been set up composed of representatives from CtrlAQUA SFI and key industry actors in land-based salmon production in Norway. During Year 1, we have identified the levels of H2S under normal operational conditions from the monitoring programme conducted in two RAS facilities. This programme likewise allowed us to identify different hotspots that might be crucial for H2S formation in RAS. The H2S levels identified were compared with the conditions of operational welfare indicators and histopathological status of the different tissues. Moreover, benchtop bioreactor studies shed insights into the kinetics and factors that influenced H2S formation. Physiological studies were conducted in respirometer to define the toxicity level of H2S, especially on how it targets the oxygen consumption of salmon. Several in vitro cell models have been employed to study the mechanisms of how H2S affects salmon physiology. Biological pathways and molecular biomarkers have been identified, providing the first and in-depth insights on H2S-salmon interactions.

Problems related to hydrogen sulphide (H2S) have become increasingly prevalent in Norwegian Atlantic salmon recirculating aquaculture system (RAS) facilities, with several cases of mass mortality reported in the last years. There is, however, a significant lacuna in the current understanding concerning the biology and physiology of H2S-fish interactions, specifically in salmon. To solve this challenge, a unique and strategic project consortium has been assembled, including two of Norway’s leading R&D institutes on the environmental and biological aspects of recirculation technology (Nofima, NIVA) and a top-rank academic institution with strong expertise in fish physiology (DTU). In addition, an Industry Reference Group will be set up composed of key industry actors in land-based salmon production. In Work Package 1, a programme for detailed monitoring of H2S and tank water quality will be implemented in several salmon farms operating in RAS in Norway and Denmark. This will be supplemented with routine monitoring of health and welfare status of fish reared in those systems and a series of batch reactor experiments to identify how H2S is formed under different production scenarios. Work Package 2 aims to provide molecular and mechanistic insights into exogenous H2S-host interactions in salmon. We will elucidate how salmon cells respond to H2S and identify molecules that may be exploited as biomarkers for H2S response. We will combine the characterised genetic markers and behavioural reaction to further elucidate the sensing response of salmon to environmental H2S. Work Packages 3 and 4 will employ a series of small-scale and large-scale studies to identify the impacts of acute and chronic exposure to H2S on metabolism, welfare and production performance (WP3), as well as on mucosal health and stress resilience (WP4) in salmon. The expected results will offer new frontier in H2S research in fish, particularly in developing knowledge-based mitigating measures.

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HAVBRUK2-Stort program for havbruksforskning