GIS-based decision support tool for optimisation of marine cage siting for aquaculture: A case study for the Western Isles, Scotland

Scotland’s coastal environment has many areas which are potentially suitable for sustainable aquaculture development. However previous studies have shown that aquaculture may have a detrimental impact on sensitive environments. The main objective of this study is to develop a holistic management tool for sustainable coastal marine aquaculture in the Western Isles of Scotland through development of a multi-faceted holistic model that allows consideration of sensitive environments. As the Scottish Government promotes better collaboration and integration of all involved in coastal zone governance (Baxter et al, 2008) this study illustrates the benefits to be gained from harmonized management of information in a Geographical Information System. GIS models are strong support tools designed to aid decision-making. The main strengths are that GIS can generate easily understandable visual displays of results which are based on robust models capable of incorporating vast amounts of spatial data and which can be predictive and can simulate future coastal environment scenarios. Within this study it is demonstrated that GIS-based models can successfully manage and manipulate a wide range of datasets that are essential components in the determination and management of suitable aquaculture locations. The GIS decision support tools evaluated and integrated in this study were based on four main sub models. These were Cage Site Suitability, Particulate Dispersion, Sensitivity Biodiversity Indicators and Visual Landscape Capacity. Exploration of a combination of these sub-models into an overall decision support system was also completed. All sub models developed were flexible, instrumentally coherent and communicatively balanced for the management and planning of the coastal environment . A sub-model was designed to evaluate and optimize the location of marine cage systems. This required development of data layers and modelled sub-components relevant to the important environmental and engineering factors affecting cage designs which included wave climate, bathymetric and substrate profiles. Three cage types were explored; those designed for sheltered, semi-exposed and exposed areas. These environmental factor layers were combined through weighting and Multi criteria evaluation consideration for each cage type. The resulting three sub-models indicated that while the archipelago has