The influence of two sea-cage fish farms at Gran Canaria Island (Canary Islands, central east Atlantic Ocean) on the intertidal macrobenthic assemblages was studied. Two controls and two impact locations were established at each farm. The composition and coverage of the macrobenthic assemblages were surveyed every three months using image processing analyses. Significant dissimilarities were found between control and impact locations at both sea-cage fish farms. The presence of: (1) algal species tolerant to pollution (Caulerpa racemosa and Corallina elongata); and (2) filter-feeding fauna (Anemonia sulcata) at impact locations, indicate that the fish farming activity is causing an effect on the surrounding intertidal macrobenthic assemblages of both sea-cage fish farms.