Optimisation of treatment of Ichthyophthirius multifiliis in farmed freshwater fish: Final Report to the Fisheries Research & Development Corporation

Rainbow trout (Oncorhynchus mykiss Walbaum)are an ideal species for cultivation and are an important aquaculture species in Victoria, Australia (ABARES 2011). Rainbow trout are primarily cultured in flow-through systems with incoming water sourced from a river or lake. The cultured fish are therefore exposed to pathogens from outside the culture environment. Rainbow trout are susceptible to a number of diseases, in particular the ciliate parasite Ichthyophthirius multifiliis (Fouquet). Management of I. multifiliisprior to 2011 was often ineffective and I. multifiliis caused major stock losses. A meeting of the Victorian Trout Growers Association (VGTA) identified I. multifiliisas a limiting factor for the growth and sustainability of the industry. This study focused on developing effective treatment systems and is an extension of a previous DPI Victoria (Now DEPI) project Improving the resilience of aquaculture sectors to climate variability -better practice fish health management for salmonid farmers.