Study

Evaluation of short-term fallowing as a strategy for the management of recurring organic enrichment under salmon cages

  • Published source details Macleod C.K., Moltschaniwskyj N.A. & Crawford C.M. (2006) Evaluation of short-term fallowing as a strategy for the management of recurring organic enrichment under salmon cages. Marine Pollution Bulletin, 52, 1458-1466.

Actions

This study is summarised as evidence for the following.

Action Category

Leave a fallow period during fish/shellfish farming

Action Link
Subtidal Benthic Invertebrate Conservation

Establish fallowing to reduce pollution

Action Link
Sustainable Aquaculture
  1. Leave a fallow period during fish/shellfish farming

    A replicated, before-and-after, site comparison study in 2003–2004 at two soft seabed locations in the Tasman Sea, southeastern Tasmania, Australia (Macleod et al. 2006 – same experimental set-up as Macleod et al. 2007) found that after a three-month fallow period, invertebrate community composition had changed at farmed sites. After the fallow period (no fish in cages), communities were different to that of the pre-fallow period (fish in cages), and similar to communities present before fish were added (empty cages). Community data were reported as statistical model results and graphical analyses. In addition, although similarity in invertebrate community between farmed sites and sites without fish farms (natural seabed) increased after fallow (from 25% to 31% similarity at one location, and from 11% to 27% at the other location), communities remained different. Sediment samples were collected using a grab (0.07 m2). At each of the two locations, five samples were collected at farmed and unfarmed sites before fish were added, following nine months of fish farming (pre-fallow period), and following the three-month fallow period. Invertebrates (>1 mm) were identified and counted. This was repeated over a second farming/fallowing cycle.

    (Summarised by: Anaëlle Lemasson)

  2. Establish fallowing to reduce pollution

    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.

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