Risk factors for escalating saprolegniosis outbreaks in salmon farms (RIFE-SOS)

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Fish diseases are a huge threat for the aquaculture industry and for global food security. Some of the most important disease-causing organisms in aquaculture are part of the oomycetes or watermoulds, in particular Saprolegnia parasitica, Saprolegnia diclina and Saprolegnia australis are causing serious fish losses. Collectively, these fungal-like organisms are responsible for at least 10% annual mortalities in most salmon hatcheries and freshwater sites. Consequently, Saprolegnia ranks among the most important pathogens of Atlantic salmon.Unfortunately, over the last few years the incidences of saprolegniosis outbreaks in Scottish farms have significantly increased. Indeed, some sites have had very high losses due to saprolegniosis. Whereas other farms have remained largely disease free. The reasons as to why some farms are badly affected and others seem to avoid disease outbreaks, with apparent identical welfare standards and husbandry management practises, are at present completely unclear and form the main rational for the current application.Our hypothesis is that several risk factors (pertaining to fish, pathogens and the environment) are playing a synergistic role in suppressing immunity in fish towards Saprolegnia, which lead to outbreaks of saprolegniosis. Therefore, we propose a concerted industry-wide, industry-led and industry-supported research programme to discover, map, model and understand the main drivers, risk factors, that allow saprolegniosis outbreaks. A "big data" resource will be created that will be scrutinised with statistical methods to identify the main risk factors and conditions for outbreaks of saprolegniosis. Undoubtedly, identifying the main, or a combination of, risk factors will greatly aid the salmon aquaculture industry to pre-empt any future outbreaks and would lead to an integrated approach to saprolegniosis management, which would result in increased welfare standards, improved fish health, fewer losses and a reduction in production and treatment costs.