The widely recognised, highly beneficial effects of fish as components of a healthy diet are almost exclusively derived from their high content of long-chain omega-3 polyunsaturated fatty acids, EPA and DHA, which are known to be essential for proper neural development, and protective against several inflammatory conditions including cardiovascular diseases and some neurological disorders. However, over-exploitation of wild fisheries has meant that an ever-increasing proportion of fish in the human food basket is now farmed. Atlantic salmon, a so-called 'oily fish' and arguably the best source of essential omega-3 fatty acids, are the major farmed fish species in the UK. Paradoxically, diets for farmed carnivorous fish, including salmon, have traditionally been based on fishmeal and fish oil, themselves derived from marine fisheries. Continued development of aquaculture requires feeds to move from these finite, limited and dwindling marine resources to environmentally friendly and ecologically sustainable ingredients, specifically plant meals and vegetable oils, derived from terrestrial agriculture. However, the oil components of plant-based feeds differ substantially from those of marine-based feeds, completely lacking the long-chain omega-3 fatty acids, which has important consequences not only for health of fish, but also the health of human consumers. Therefore, the challenge for aquaculture is how to farm fish in a sustainable and environmentally friendly manner and yet maintain the high levels of long-chain omega-3 fatty acids that confer their nutritional quality and status as beneficial and healthy components of the human diet. The aim of this project is to produce novel vegetable oils specifically enhanced to fit the needs of the aquafeed industry by containing high levels of long-chain omega-3 fatty acids, EPA and DHA, and that can be used to replace our finite reserves of marine fish oil and prevent the over-exploitation of this natural resource. The first goal of the research will be to develop varieties of oilseed plants that can manufacture and accumulate EPA and DHA in their seeds. The oilseed crop of choice, Camelina sativa, also known as false flax or gold-of-pleasure and a relative of rapeseed traditionally grown for oil in Europe, will be modified using a synthetic biology approach that will result in plants metabolically engineered by the inclusion of algal genes to manufacture the long-chain omega-3 fatty acids, EPA and DHA, usually produced only in marine microalgae. The second specific goal will be to formulate plant-based feeds containing the novel, long-chain omega-3 Camelina oils and to test them in feeding trials with Atlantic salmon, which will determine the efficiency, nutritional quality, and safety of the feeds. A third goal will be to study the metabolism of EPA and DHA in fish cells where we can manipulate the fatty acids supplied very precisely and elucidate the biochemical pathways and molecular mechanisms involved in determining the fatty acid composition of cells and, in particular, the conversion of EPA to DHA. These cell studies will inform the metabolic engineering experiments by providing data on the levels and ratios of EPA and DHA required in the novel oils for optimal performance in aquafeed formulations. Since farmed salmon are a major source of long-chain omega-3 in the UK diet, with more than 1.2 million salmon meals eaten per day, this project can make a significant contribution to the health and well-being of the human population in the UK. In addition, 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.