A general description of rocky shore distribution patterns (“zonation”) along the whole Portuguese coast is given to provide the context for comparisons of distribution patterns of mid-shore organisms. In order to test if there was any variation in species distribution and abundance in the upper and lower mid-shore zone (eulittoral) along the entire intertidal Portuguese coast, three main regions were studied (north, centre and south) and nine shores were visited in each region. At each one of the 27 locations, the shore was levelled and a general qualitative description was made, which also aided stratification of subsequent quantitative sampling. An upper zone (littoral fringe) characterised by the presence of encrusting lichens, small littorinid gastropods and cyanobacteria was found on most of the shores along the Portuguese coast. The mid-shore zone (eulittoral) is essentially dominated by barnacles and sometimes mussels. The distribution patterns observed on the lower shore (sub-littoral fringe) showed a distinction between northern shores, where large brown algae are present, and shores located in the central and southern regions, essentially dominated by red algal turf species. Multidimensional analysis and the ANOSIM test have revealed clear differences in the structure of the upper and lower mid-shore zone. Within each level, the northern region was considerably different from the south and central regions. SIMPER analysis revealed the species which contributed to the separation between shore levels and regions. It has also given important information on the geographical decline in abundance of species.
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