Artificial reefs (AR) for diving must have certain characteristics that are not activity-limiting. Likewise, these characteristics are generally fundamental for good diving experiences. In this aspect, AR must not be at a great depth, and they must have a diverse bio-colonization by several species of various taxa and attract diver interest. In Portugal, Algarve (South) and Nazaré (Centre) reef modules were deployed at depths that can be considered as potential for diving. In this chapter, an approach is made using the analytic hierarchy process (AHP) and fuzzy logic (a method called fuzzy analytic hierarchy process: FAHP) defining what is the likely interest for potential diving tourism activities in each of the locations presenting AR modules. The results obtained by using these methods allowed to further discover the importance of AR in Algarve and Nazaré.
TopIntroduction
The concept of artificial reefs (AR) originates in Japan and dates to a few centuries ago (White et al., 1990). However, it was only in the 20th century that large-scale projects began to be developed (Sheehy, 1982; Thierry, 1988). The countries that developed reef programs were Japan for commercial fishing purposes and the US primarily for recreational activities (McGurrin et al., 1989; Polovina & Sakai, 1989; Bohnsack, 1991). Since the 1960s, AR have started to expand to other geographies and are currently dispersed all over the world (e.g., Bohnsack & Sutherland, 1985; Fabi & Spagnolo, 2011; Bortone & Otake, 2020).
AR are in coastal areas, lakes, or other bodies of water and serve different purposes depending on the entities involved in their construction and implementation (Frank, 2018). One of the fundamental issues that enter the decision process is whether there is a need to implement AR (Gordon Jr. & Ditton, 1986). This decision depends on the expressed willingness of the stakeholders and the balance between demand and supply in the market (e.g., Sutton & Bushnell, 2007; Tunca et al., 2014).
AR are often used as protection tools, deployed on the seabed to divert fishing or recreational practices that may cause damage (Streich, 2017; Tynyakov, 2017). Another function of AR is to provide protective shelter for small marine organisms in transitional waters between nurseries and the ocean (Santos et al., 2005). Reef modules can also have another function, named as serving for recreational diving (e.g., Stolk et al., 2007; Tunca et al., 2012; Bideci & Cater, 2019).
In the case of diving, it is important to understand whether the tourism industry is looking for alternatives or complements to the places that are already visited (Oliveira et al., 2015); and knowing what kind of structures can be implemented and which locations are the most suitable for doing so (Kirkbride-Smith et al., 2013).
The use of AR for diving is particularly relevant in several respects. Specifically, when the structures are deployed to divert divers from places with natural reefs to places artificialized with these structures, but which in a way mimic the natural reefs and thus attract dive tourists (e.g., Perkol-Finkel et al., 2006; Salaün et al., 2020). There are many types of functional structures for certain purposes of protecting living organisms and mitigating potentially harmful practices in the marine environment (e.g., anti-trawling modules) (e.g., Ramos-Esplá et al., 2000), but not all reef structures are consistent to serve tourist diving (Ramos et al., 2006).
The first artificial reef modules in Portugal were supported by the fisheries and aquaculture research institute (then INIP) and were implemented in 1990 (Santos et al., 1995). The last AR were placed in 2010 and were backed by a municipality with the support of the fisheries and aquaculture research institute (then INIAP) (Ramos et al., 2019). The first purposes of these modules were to protect mollusks, crustaceans, and young fish of various species, to serve as a complement to the diversification of fisheries in small-scale commercial fisheries, and eventually to provide diverse ecosystem services and other functions. Among these other functions, we highlight the promotion of recreational activities, such as diving (Almeida et al., 2016).