Action: Establish fallowing to reduce pollution
A trial in Tasmania found sediment community structure under Atlantic salmon cages became more similar to non- impacted sites over two fallowing cycles.
Husbandry practice on salmon farms is important in reducing the spread of disease within and beyond the farm. Fallowing has been practiced in terrestrial agriculture for centuries to reduce the incidence of disease. Many salmon farms use fallowing as a technique for disease control and some to reduce the build-up of sediments below cages. Chemical and biological remediation of benthos near salmon farms has been proven. A two month fallowing cycle is mandatory to break parasite cycles on salmon farms.
Supporting evidence from individual studies
A controlled, replicated trial between 2003 and 2004 at two fish farm sites in southeast Tasmania (Macleod et al. 2006) found sediment community structure under Atlantic salmon cages became more similar to non- impacted sites over two fallowing cycles. Similarity of the community structure of the impact sites to the reference sites increased from 25% to 31% at one site and 11% to 27% at the other after fallowing. The extent and rate of recovery were affected by length of fallow period, farm location and the initial impact of the sediments. An annual stocking regime was employed at both farms where cages were stocked for nine months and then fallowed for three months. Sediment samples were collected from cage positions and reference sites before the cages were stocked, after nine months of stocking and at the end of the three month fallow period. Samples were taken at monthly intervals during the second year. Circular study cages with a circumference of 120 m were used at both farms.