Geographical information systems-based models for offshore floating marine fish cage aquaculture site selection in Tenerife, Canary Islands

Abstract

The present study focuses on the development of a standard methodology for selection of suitable sites for oishore (exposed) marine ¢sh-cage farming (£oating cages) of seabream (Sparus aurata )a nd seabass (Dicentrarchus labrax) in an island environment, using Tenerife as an example. Site selection is a key factor in any aquaculture operation, aiecting both success and sustainability and can solve con£icts between diierent activities, making a rational use of the coastal space. Site selection was achieved by using geographical information systems (GIS)-based models and related technology to support the decision-making process. The framework for spatial multicriteria decision analysis used in this study began with a recognition and de¢nition of the decision problem. Subsequently, 31 production functions (factors and constraints) were identi¢ed, de¢ned and subdivided into eight submodels. These were then integrated into a GIS database in the form of thematic layers and later scored for standardization. At this stage, the database was veri¢ed by ¢eld sampling to establish the quality of data used. The decision maker’s preferences were incorporated into the decision model by assigning weights of relative importance to the evaluation under consideration. These, together with the thematic layers, were incorporated using multicriteria evaluation techniques and simple overlays to provide an overall assessment of possible alternatives. The integration, manipulation and presentation of the results by means of GIS-based models in this sequential and logical £ow of steps proved to be very eiective for helping the decision-making process of site selection. Tenerife has very favourable environmental conditions for culture of marine ¢sh and there are no totally unsuitable sites for cage farming identi¢ed in this study. On the other hand, there are few very suitable sites (high scores) either, principally due to the heavy use of the coastline and the con£icts between diierent users. From the 228 km 2 of available area for siting cages in the coastal regions with depth less than 50 m, the total area suitable for siting cages (scores 6^8) was 37 km 2 . There are only 0.51km 2 of very suitable areas (score 8) and approximately 5.37 km 2 of suitable (score 7), most of these being located in the southeast of the island. These relatively small areas of suitability should be put into the context of the wider use of the coastal environment around Tenerife.