On the calculation of wa v e climate for offshore cage culture site selection : a case study in Tenerife ( Canary Islands )

The lack of suitable sheltered sites is forcing fish farmers to move to more exposed offshore locations in order to provide for continued growth in the industry. However, as farmers move to more exposed sites for ongrowing, extreme weather conditions must be regarded as a normal environmental condition. For appropriate cage system selection and siting sufficient wave data has to be available, as wave action (wave climate) on floating cage structures may create conditions where failures are likely. At present, there are many methods of estimating wave climate, but none has been clearly presented for its use in offshore cage culture siting, particularly in a format that may be used within an integrated selection tool. This paper presents a novel methodology for wave climate characterisation in offshore fish cage site selection, based on a case study for sitting offshore seabass and seabream cages in Tenerife (Canary Islands). The mid-term statistic was used to identify prevailing wave heights and the long-term statistic or extreme wave analysis was used to identify the likely highest waves over a certain time period (15 years). The former can promote gradual failure of structures, while the latter may cause instant total failure. Based on this information, three cage systems were selected and, a suitability map was created for each using Geographical information systems, showing the more suitable zones to site the cages. # 2003 Elsevier B.V. All rights reserved.