Assessing the Level of Risk of Introduction and Spread of Exotic Oomycete Species via Ornamental Fish Imports to Wild Fish Populations and Fish Popula

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Millions of ornamental fish are being imported every year into the UK, potentially carrying a huge range of pathogens. It is known to the Cefas FHI that some of the imports from south east Asia are imported carrying viral pathogens. Less is known about the Oomycete pathogens that are being imported. Two species of oomycetes have independently emerged as highly successful pathogens of finfish in aquaculture. Saprolegnia parasitica is responsible for high levels of mortality in salmon in the UK and elsewhere. Aphanomyces invadans is responsible for the OIE notifiable disease epizootic ulcerative syndrome (EUS), which is spreading geographically and is already well established in Asia and Africa. The ranges of fish species susceptible to the two pathogens are large and overlapping but not identical. Both pathogens not only affect farmed fish but also natural populations.The purpose of this PhD project is to assess the level of risk from such imports by testing samples from recent imports. Samples from wild fish populations and fisheries will be tested to assess the presence of these pathogens in the natural environment. Phylogenetic analyses will be applied to relate imported strains to those found in the wild. This will allow to assess the potential threat from imported Oomycete pathogens for fish populations in fisheries and the wild.