Counts = counts/sample = #/9 m^2.Boulders colonized by M. pyrifera were transported into three replicated experimental areas (9 m^2^ each) located in a barren ground area. Three barren ground areas (9 m^2^ each) without manipulation were selected as controls. Fish abundance, composition, and spatial distribution were recorded weekly by scientific SCUBA divers between 15/02/2007 and 11/04/2007 always choosing days with calm sea conditions. Within sampling units (3 x 3m) one SCUBA diver counted all sporophytes present, while a second diver (always the same) recorded all fish species following modified procedures developed by Sale and Douglas (1981). The diver approached the marked site and at a distance of four meters slowly unidirectionally circled the sampling unit while marking the spatial distribution of fishes on a check list for five minutes. The diver then moved closer to the unit to record demersal species and searched the algae themselves. Because of difficult field identification of the Giant Blenny Scartichthys gigas (Steindachner, 1876) and the Green Blenny Scartichthys viridis (Valenciennes, 1836) due to their colour phases, sexual dimorphism and similar looking young stages, they were recorded as Scartichthys gigas/viridis. The diver swam calmly along the sampling unit, while observing from the ground up to the water surface, which included the canopy level in case of the experimental sites. The spatial distribution of the fish species was categorized according to Nuñez and Vásquez (1987) in 1) rock (fish associated directly with rock substratum feeding and/or settling on it), 2) macroalgae (fish associated directly feeding and/or settling on macroalgae), 3) water column (fish above rock or macroalgae).