ROBUST-SMOLT: Impact of early life history in freshwater recirculation aquaculture systems on salmon robustness and susceptibility to disease at sea.

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The adoption of Recirculation Aquaculture Systems for freshwater salmon production has clear benefits however, fish transferred from RAS systems are not performing equally to fish reared in open water loch systems. In the current project, we hypothesise that RAS rearing conditions, especially water chemistry and microbiology, nutrition, photoperiod and temperature, affect early life history traits of salmon and impact on microbiomes, immune barriers, osmoregulation, and robustness at sea especially for gill pathologies and new anaemic syndrome. The proposed research is multidisciplinary and will develop basic knowledge on RAS, photo-thermal history, diet and vaccine effects on fish physiology that may predispose fish to disease at sea. Two large-scale trials will be performed to test RAS vs. open water lochs in a commercial setting and the interaction between photoperiod, diet and vaccine in a controlled experiment. In addition, small-scale experiments will test the effects of increased CO2 on salmon physiology, the effects of freshwater history on smolt immune function (using double stranded RNA challenge) and post-smolt amoebic gill disease susceptibility when challenged with infectious agent N. Peruvans. A toolbox will be used to study fish health biomarkers including blood chemistry, haematopoietic indexes, endocrine status and immune function including leukocyte inflammatory markers, anti-viral response in erythrocytes and plasma prostaglandins. The genotype by environment interaction will also be studied. Experimental and production data will be combined in a meta-analysis to produce a unique large-scale epidemiological study and identify risk factors for disease at sea. Major outcomes will be industry recommendations, protocols and tools for early freshwater conditioning that promote enhanced immune function and health at sea. The ROBUST-SMOLT project will contribute to boost the competitiveness and sustainability of the UK aquaculture sector.

The project will have significant economic, social and environmental impacts by furthering our understanding and improving inconsistences in smolt quality supply and subsequent seawater performance and losses. Thus, the overarching goal is to provide new knowledge and tools to monitor and enhance farming system (RAS) efficiency and reliability, fish robustness and health, and sector productivity and sustainability. Furthermore, the project aims to improve our basic understanding of mechanisms of the gut microbiome, mucosal integrity, physiological regulation of smoltification and interaction with water chemistry under closed RAS systems to enhance immunocompetence and post-sea transfer performance. By gaining an insight into molecular regulation and phenotypic development under closed containment systems, the salmon producers will also benefit from development of new tools and markers to aid improving smolt health and consistency, thus ensuring that fish produced are in optimum condition and meeting welfare standards. Such knowledge will help reduce losses and increase viability, competitiveness and sustainability of the UK aquaculture production sectors. The UK is the world's second largest salmon producer with ex-farm value of £400 million, worldwide retail value of over £1 billion, and contributes over £500 million to the UK economy. Salmon comprises 40% of Scottish food exports, a 500% increase in the last 20 years, and exports to 55 countries. Most importantly, fish farming supports employment for over 8,000 people in rural areas in which jobs otherwise are few, and injects £5m every week into these communities as wages and local expenditure. Furthermore, the UK salmon industry has been tasked to farm 70,000 extra tonnes by 2020 (market value of £280M+) and >100,000t by 2030. This can only come from opening new locations and improving production efficiency - requiring a significant "paradigm" shift in public perception of the sustainability and welfare of farmed salmon. Losses at sea in 2016 accounted for ~36,000T (16.8% of smolts put to sea), 50% of the desired UK production target for 2020. Thus, collaboration between the industry and academic research in this area is vital as aquaculture is not supported by any Government research institute, as in other areas of agriculture. As such, the primary economic beneficiaries will be the UK aquaculture industry, specifically through producers (MHS, SSF, SSC & Cooke), Biomar Ltd. and Pharmaq Ltd., allowing them to strength UK competitiveness in the global market, by keeping pace with, and refining operative efficiency, as part of the progressive nature of global aquaculture. The project benefits will therefore get passed directly to the UK salmon producers through the generation of new husbandry protocols, health management strategies, feed and vaccines. The project will directly benefit the competitiveness of the entire UK salmon industry chain. This project will also contribute to UK policies for sustainability and environmentally sound food production, whilst ensuring health and welfare of fish. Improved control will also support the Renewed Strategic Framework for Scottish Aquaculture (2010) and the Future of European aquaculture (EATiP, 2012). The data will also aid the industry portray a more pro-active approach to addressing the public concerns of welfare of farmed salmon. Finally, there will also be direct public health benefits by increasing productivity. Since farmed salmon are a major source of long-chain omega-3 in the UK diet, with more than 1.2m salmon meals eaten per day, this project can also make a significant contribution to the health and well-being of the human population. Overall, the major outcome of this project will be to provide data to industry in order to optimise practical methods for the routine production of high quality smolts in RAS systems and maximise robustness of farmed stocks during seawater ongrowing.