Effect of simulated macroalgae on the fish assemblage associated with a temperate reef system T. Vega Fernández a, ⁎, G. D'Anna a , F. Badalamenti a , A. Pérez-Ruzafa b a CNR — IAMC, Laboratory of Marine Ecology, Via G. da Verrazzano 17, Castellammare del Golfo (TP), 91014, Italy b Department of Ecology and Hydrology, University of Murcia, Campus Universitario de Espinardo, Murcia, 30011, Spain abstract article info Article history: Received 2 April 2008 Received in revised form 21 May 2009 Accepted 22 May 2009 Keywords: Assemblage structure Artificial algae Canopy restoration Habitat complexity Habitat structure Repeated measures Increased habitat complexity is supposed to promote increased diversity, abundance and biomass. This study tested the effect of the macroalgal cover on temperate reef fishes by mimicking macroalgae on artificial reefs in NW Sicily (Mediterranean Sea). Macroalgal cover affected reef fishes in different ways and independently of intrinsic temporal trends. The fish assemblages of manipulated and control artificial reef units differed in the relative abundances of the associated species, but little in species composition. In line with studies in seagrass habitats, fishes were most abundant in reefs covered by artificial macroalgae. Three species (Boops boops, Serranus scriba and Symphodus ocellatus) exhibited consistently greater abundance on vegetated reef units than on control reef units. The total number of species and the abundance of three particular species (S. scriba, S. ocellatus and Thalassoma pavo) displayed temporal trends which were independent on short and large temporal scales. Only fish total biomass and one species (Spicara flexuosa) displayed strong effects of interaction among the experimental factors. Mechanisms to explain these findings are discussed from observational evidence on habitat use and interactions among multiple species. This study highlights that manipulative experiments involving repeated sampling of fish in artificial habitats appear to be a valid approach to study fish-habitat relationships in fluctuating environments. It is also concluded that macroalgae mimics may serve as a tool for restoring lost marine vegetated habitats when current human-induced conditions prevent the recovery of pristine macroalgal stands. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Increased habitat complexity has long been recognised to exert a positive influence on the diversity and abundance of marine organisms. Habitat complexity promotes resource partitioning by ameliorating competition (Schoener, 1974), and leads to stabilization of predator–prey dynamics (Sih, 1987). Structural complexity (sensu McCoy et al., 1991) is provided by plants in most ecosystems by means of their density and form (Silvertown, 2004). Thick vegetation is still permeable for small or appropriately shaped animals whilst larger or unsuitably shaped species are physically excluded. Hence vegetative cover is frequently used for refuge and foraging under predation risk (Lima and Dill, 1990). In temperate shallow aquatic environments, vascular macrophytes and macroalgae supply the bulk of the habitat complexity above the bottom (Ebeling and Hixon, 1991). These marine vegetated commu- nities support more diverse and abundant fish assemblages than surrounding unvegetated areas of similar depth, and share many common species irrespective of vegetation type (Jenkins and Wheatley, 1998; Guidetti, 2000). This suggests that many fish species select the structure provided by vegetation rather than specific vegetative species (Heck et al., 2003). Indeed, field experiments indicate that plant volume and cover are among the most important factors driving the structure of temperate fish assemblages (Choat and Ayling, 1987; Carr, 1989), and are particularly important for small- bodied fishes (Shulman, 1985; Carr, 1989; Adams et al., 2004; Crawley et al., 2006). The effect of plant complexity on fishes may be explained by habitat related resource availability (Jones, 1991). The type of resource also exerts great influence on species-specific and size-specific interactions (Werner et al.,1983b; Persson and Eklöv, 1995). Shelter and food are the most important niche axes in fishes (Wootton, 1998) and many species exploit both resources in vegetated habitats (Lenanton and Caputi, 1989; Crawley et al., 2006). When several resources are present in multiple habitat types, vegetated areas are still preferred by some species, thus it is supposed that their individual fitness is improved there (Werner et al., 1983a; Alofs and Polivka, 2004). More usually, predation refuge and food occur in distinct, alternate habitat types. The role of plant cover as refuge then takes precedence in the presence of predators (Werner et al., 1983b; Shulman, 1985; Gerking, 1994). How predation success is affected by habitat complexity is strongly species dependent (Diehl, 1988; Eklöv and Diehl, 1994). In general, Journal of Experimental Marine Biology and Ecology 376 (2009) 7–16 ⁎ Corresponding author. Tel.: +39 092435013; fax: +39 092435084. E-mail address: tvega@irma.pa.cnr.it (T. Vega Fernández). 0022-0981/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jembe.2009.05.012 Contents lists available at ScienceDirect Journal of Experimental Marine Biology and Ecology journal homepage: www.elsevier.com/locate/jembe