Using physical environmental parameters and cage engineering design within GIS-based site suitability models for marine aquaculture

Defining the physical suitability of an area for marine cage fish farming is of great importance, as each cage type has its own engineering tolerance levels and is designed to cope with a certain range of environmental conditions. Currently, there are no definitive, objective methods used to evaluate the suitability of coastal and offshore sites with respect to the physical limits of the location and the engineering design of a specific cage type. This study developed models which incorporate physical environmental parameters and cage engineering design within a GIS (graphical information system) environment, providing a valuable decision support tool for farmers, regulators and policy makers. The Western Isles of Scotland, UK, were selected as a study area due to the wide range of coastal and offshore environments. In addition, we selected 4 cage types designed for different wave exposure conditions (sheltered, moderately exposed, exposed and offshore). The models have been developed for worst-case scenarios, such as maximum significant wave height, conditions which are often difficult to predict. As shown in this study, the models can be used to assess the risk of using the selected cage type in a certain area and to highlight specific locations for development. The results indicate there is scope for further expansion of the aquaculture industry in the Western Isles using cages designed for exposed and offshore conditions, whereas there is limited potential for new developments using cages designed for moderately exposed environments. This allows stakeholders to make a robust decision about what cage type to use and where to locate it.