Distribution of Neoparamoeba sp in sediments around marine finfish farming sites in Tasmania

Marine sediment samples collected from various sites at 2 Atlantic salmon farms in Tasmania were analysed for the presence of Neoparamoeba sp., an amoeba associated with amoebic gill disease (AGD) in farmed Atlantic salmon. Environmental variables of the sediment layer at each site, including redox potential and sulphide concentration, were measured and the general biological condition assessed by video observation. Sediments and environmental data were collected on 4 occasions at each site over a 12 mo period. Neoparamoeba sp. was detected in populations of amoebae recovered by culture from all sites and in 50% of all sediment samples taken. There was evidence of a seasonal influence on the presence of the amoeba, but this was different at each farm. No Neoparamoeba sp. was recovered from any sites at Farm 1 during the winter of 2002 whereas at Farm 2 this was the case for the summer of 2003. There appeared to be no relationship between the presence of Neoparamoeba sp., salmon farming activities and environmental parameters.