SARF009: Coastal Assimilative Capacity for Amalgamated Fish Farm Chemicals/Organic Pollutants

Start Date: 01/04/2005
End Date: 31/03/2008
Main Contractor(s): University of Aberdeen
Other Sponsor(s): Oceanlab

Objectives

The following objectives will explicitly test key hypotheses:

1) Hypothesis 1: The gradient of environmental impact of fish farms does not depend on farm size. The first objective will be to establish the footprint of impact of contrasting sized farm units using state-of-the -art sediment profile imaging technologies, ecotoxicological screening of sediment and water samples, and geostatistical interpolation. This approach does not necessitate studying an amalgamated farm in a specific location because it unequivocally establishes the relationship between farm size and zone of impact.

2) Hypothesis 2: The magnitude of environmental impact of fish farms does not depend on farm size. The second objective will be to build on objective 1 by using a validated mesocosm approach that explicitly tests the level of ecosystem response to a wide range of discharge concentrations of sea lice treatment chemicals and other organic pollutants. This establishes a predictive basis because these relationships can be investigated using standard regression procedures.

3) Hypothesis 3: The impact of fish farm effluents is independent of trophic level but dependent on the number of species present. The third objective will be to take representative faunal samples from along the gradient of farm impact and to establish mesocosm treatments comprising simple multitrophic assemblages (micro-organisms, invertebrates) around a basal resource. This statistically robust approach enables the establishment of the relationship between trophic complexity, biodiversity and ecosystem function.

4) Hypothesis 4: That the impact of fish farm effluent can be predicted by the simple summation of the toxic effects of individual contaminants. The fourth objective will be to use a ecotoxicological approach using a dose response investigation with single and mixed cocktail of contaminants identified from the field. The advantage of this approach is that it allows ecotoxicity to be assessed at levels (microbial, macro-invertebrate and fish) integral to ecosystem health. In addtion, this approach explicitly recognises that a combination of contaminants may not necessarily result in the same ecological impact as that predicted from the summation of the toxic effects of multiple contaminants investigated in isolation.

5) Hypothesis 5: The impact of fish farm effluent is independent of location. The fifth objective explicitly recongnises that the environmental impact of a poorly sited farm may significantly differ to that of a farm sited at an alternative location. Using the approach adopted for hypothesis 3 (above), specific levels of impact can be assessed for contrasting species assemblages that reflect alternative benthic communities.

6) Hypothesis 6: That the ecosystem response to commercial fish farming activity cannot be predicted. The sixth objective will involve derivation of the empirical relationship between scenario of fish-farm associated impact and ecosystem response. This will enable us to parameterise numerical simulations that predict how fish farm amalgamation is likley to impact on the environment and hence how to design amalgamated fish farms where impact exceeds current practice.

Summary

Intensification of fish farming activity and the amalgamation of farm units has the potential to cause an increased risk of organic contaminant pollution. Although the amalgamation of fish farm units into a fewer number of larger operations offers greater financial efficiency to an already troubled industry, concern exists over whether the discharge of sea lice treatment chemicals and other synthetic organic compounds from large scale operations may have a greater environmental impact than an equivalent use of such compounds at several smaller farm units. To address this concern, it is necessary to assess how fish farm amalgamation can be implemented in an evironmentally sustainable manner. This is an issue facing the entire marine aquaculture industry to ensure that it can effectively deliver on its obligations to the Strategic Framework for Scottish Aquaculture (Scottish Executive, 2003). This proposal seeks to establish the relationship between farm size and zone of impact before establishing highly controlled replicated mesocosm studies aimed at establishing the relationship between synthetic organic componds, including sealice treatment chemicals, and the functioning of the coastal benthos. These experiments avoid the problems associated with confounding and covarying factors in the field and will form the basis for numerical simulations that predict how fish farm amalgamation is likely to impact on the environment and hence how to design amalgamated fish farms where impact exceeds current practice.