Fish community structure on littoral rocky shores in the Eastern Aegean Sea: Effects of exposure and substratum

Littoral rocky shores are important habitats for many coastal fish species providing food, shelter and nursery grounds. Nearshore fish community structure results have been mainly derived from macro-scale habitat characteristics including depth and wave exposure but the influence of, and interaction with, micro-scale habitat substratum features is not well known. This study investigated the structure and functioning of the ichthyofauna composition on rocky substrata around the island of Arki in the Eastern Aegean Sea. Quantitative surveys of fish assemblage composition were carried out by Underwater Visual Census (UVC) at 14 sites assigned to three levels of exposure. The physical substratum of every transect area was described by 14 microhabitat characteristics. Multidimensional scaling (MDS) showed that exposure to wave activity was a significant factor in structuring fish assemblages differing in feeding guilds, species richness and diversity. Substratum heterogeneity, depth, boulder complexity and verticality were the main substratum descriptors that were related with wave exposure and hence were the determining factors defining fish community structure, as revealed by Canonical Correspondence Analysis (CCA). The similarity of percentages (SIMPER) determined the species that typified the different exposure groups. This study has shown that rocky littoral shores are of high ecological importance and their conservation is of great significance to maintain coastal fish diversity.