14TSB_ATC_IR: Optimsation and implementation of sterile triploid salmon in Scotland

The production of triploid salmon, which are reproductively sterile, is a highly beneficial culture option to the industry to help prevent potential interbreeding between farmed escapees and wild salmon, thus allowing more sustainable aquaculture whilst enhancing productivity and maintaining a food product of high nutritional quality and health status. However, although triploid salmon can be easily produced and methods have been optimised, problems during culture have prevented the adoption of this technology within the farming sector in the past. The major problem experienced in triploid rearing is the occurrence of skeletal malformations. Not only do such deformities present significant implications for farmed animal welfare, but they can also reduce animal growth, decrease product processing efficiency, increase production costs and prevent ability to maintain food product quality standards. Unlike mammals, growth in fish continues throughout life and is a complex interplay between skeletal and muscle growth which is both seasonally and nutritionally driven, and therefore a mismatch of muscle and bone developmental rates can result in skeletal deformities. Since the central goal of finfish aquaculture is the production of meat, it is therefore important to understand the interactions of fish nutrition and environment on muscle development and growth. From results obtained by the group over the last 8 years, it appears very clearly that the nutritional requirements for development differ between diploids and triploids due to fundamental differences in their physiology, cellular morphology and genome organisation. In this respect, the major feature of triploids is the increased genome size (additional maternal chromosomes), the result of which not only confers sterility in the offspring but also an increase in cell size and a simultaneous reduction in cell number, potentially resulting in genome instability. It is not known what happens in Atlantic salmon and such information is vital for designing genetic improvement programs. The first goal of this research is to use natural variations in the sequence of genes to investigate which chromosomal copies are inherited and expressed in different tissues and stage of development. We will then investigate how triploidy affects the signalling pathways for hormones and genes regulating growth in muscle and bone development. We will carry out a large scale life-cycle trial in which nutrients and minerals known to be critical for the development of the skeleton will be boosted and the performance of triploids and diploids compared. Preliminary evidence already indicated the key role played by phosphorous and other minerals during the early freshwater rearing phase on reducing prevalence and severity of deformity. Research during seawater ongrowing will also focus on nutrient boosted diets to realise the full growth potential of triploid salmon. Finally, the project will characterise triploid salmon susceptibility to major known pathogens through challenge studies and test vaccine side effects as well as a range of routinely used health and husbandry practices. To ensure the success of the project, the consortium brings together world leading companies in salmon farming including Marine Harvest Scotland Ltd., Biomar Ltd. and Pharmaq Ltd. The research will enable the development of practical methods for the routine production of high quality triploids with benefits for animal welfare and the sustainability and profitability of the industry. Since farmed salmon are a major food source in the UK diet, with more than 1.2 million salmon meals eaten per day, this project can also make a significant contribution to the health and well-being of the human population in the UK. By improving the sustainability of the UK fish farming industry, this project will help to protect more than 6000 directly employed and industry-associated jobs in largely rural areas and create new jobs.

The use of triploid salmon would reduce the environmental impact of intensive farming by minimising the genetic introgression of escapees with wild populations. However, significant welfare problems associated with skeletal deformities, quality issues and a poor understanding of the genetic consequences of triploidy have prevented their adoption by the industry. The proposed research will address each of these issues with the aim of developing practical protocols to produce triploids of equivalent standard to diploids paving the way for large scale commercial trials. A family based analysis and mRNA deep sequencing will be used to investigate allele-specific patterns of inheritance to investigate mechanisms of genome stabilisation in triploids and provide practical information for future design of breeding programs. Tissues in triploids have fewer, but larger cells than diploids. The impact of cell size on signaling pathways regulating muscle growth and biomineralisation processes in bone will be investigated. Current diploid feed formulations appear to be inadequate to support the potential for more rapid growth in triploids. It is proposed carry out a commercial scale trial with industry partners to test the hypothesis that dietary deficiencies in the early life stages, particularly for phosphorous, negatively impact on normal skeleton development in seawater as well as the growth and quality characteristics of harvest size fish. Major outcomes will be the development of triploid specific diets, data to facilitate uptake of viable triploid production by the aquaculture industry, an expanded understanding of the basic science underpinning muscle and bone development and improved feed formulation to maintain optimum welfare, growth and nutritional quality of farmed salmon thereby contributing to the competitiveness and sustainability of UK aquaculture.

The project will have significant environmental, social and economic impacts by solving a major problem in the salmon aquaculture industry which currently prevents the use of sterile triploid fish in farming. Thus, the overarching goal is to gain a fundamental understanding of the mechanisms underlying these differences in order to underpin the development of novel diets for triploids which would reduce the incidence of skeletal deformities and increase growth and product quality to comparable levels to diploid salmon. Furthermore, the project aims to improve our basic understanding of mechanisms of genome stabilisation and inherited patterns of gene expression in triploids to support and enhance aquaculture stock selective improvement and help MHS to develop its own Scottish broodstock program in the future which will become increasingly important for vertical integration of the whole salmon chain and marketing/branding of a high quality Scottish salmon product. By gaining an insight into genome regulation and allelic inheritance patterns, the salmon selective breeding sector will also benefit from development of new tools and markers to aid marker assisted selection to ensure that fish are bred with continuous improvements in performance and welfare traits. Such knowledge will help reduce the environmental impact and increase the viability, competitiveness and sustainability of the UK fish feed, pharmaceutical and aquaculture production industry. 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 6,000 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 in the coming decade (market value of £280M+), this can only come from opening new locations - requiring a significant "paradigm" shift in public perception of the environmental impact of salmon farming. The 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. Thus, the primary economic beneficiaries will be the UK aquaculture industry, specifically through Marine Harvest Scotland, Biomar Ltd. and Pharmaq Ltd. who are global leaders in salmon farming. To maintain their position against competitors, they must constantly keep pace with, and adapt to, the progressive nature of global aquaculture. The project benefits will therefore get passed directly to the UK salmon producers (companies such as MHS) through the supply of new feeds, vaccine methodology and new husbandry protocols. 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 impact of escapes and help address current negative public perception associated with fish farming and animal farmed welfare. Overall, the major outcome of this project will be to provide data to industry in order to have the confidence to develop practical methods for the routine production of high quality triploids and initiate full-scale commercial trials which is the central and key aim.