Depth of sojourn and niche differentiation of benthic blennies (Pisces, Blenniidae) in the Mediterranean sea (Catalonia, NE Spain and Italian coast of the Tyrrhenian sea)

Abstract

The vertical distribution of nine species of combtooth blennies between the surface and 1,5 m depth was studied at selected rocky shore sections of the Mediterranean Sea in NE Spain and the W coast of Italy. Significant differences in mean depths of sojourn and the degree of depth overlap allow the distinction of species subgroups: species preferring the uppermost shore (Coryphoblennius galerita, Aidablennius sphynx and Lipophrys trigloides), those mostly found in a middle stratum (Lipophrys canevai, Scartella cristata, Parablennius incognitus, Parablennius gattorugine) and two species with the lowest depth of sojourn (Parablennius pilicornis, Parablennius zvonimir). The relative depth position showed little seasonal variation and was similar at both Spanish and ltalian sites. The species of each subgroup which shows a high degree of spatial overlap is distinguished in other dimensions of its ecological niches, in particular by different feeding habits and differences in shelter characteristics. On the basis of exact depth distribution data the present study indicates that depth differences of Mediterranean blennies are very finely tuned and species-specific, even on a broad geographical and seasonal scale. Key words: Vertical zonation, Rocky shore, Ecological niches, Overlap, Microhabitat, Fish assemblageThe vertical distribution of nine species of combtooth blennies between the surface and 1,5 m depth was studied at selected rocky shore sections of the Mediterranean Sea in NE Spain and the W coast of Italy. Significant differences in mean depths of sojourn and the degree of depth overlap allow the distinction of species subgroups: species preferring the uppermost shore (Coryphoblennius galerita, Aidablennius sphynx and Lipophrys trigloides), those mostly found in a middle stratum (Lipophrys canevai, Scartella cristata, Parablennius incognitus, Parablennius gattorugine) and two species with the lowest depth of sojourn (Parablennius pilicornis, Parablennius zvonimir). The relative depth position showed little seasonal variation and was similar at both Spanish and ltalian sites. The species of each subgroup which shows a high degree of spatial overlap is distinguished in other dimensions of its ecological niches, in particular by different feeding habits and differences in shelter characteristics. On the basis of exact depth distribution data the present study indicates that depth differences of Mediterranean blennies are very finely tuned and species-specific, even on a broad geographical and seasonal scale. Key words: Vertical zonation, Rocky shore, Ecological niches, Overlap, Microhabitat, Fish assemblageThe vertical distribution of nine species of combtooth blennies between the surface and 1,5 m depth was studied at selected rocky shore sections of the Mediterranean Sea in NE Spain and the W coast of Italy. Significant differences in mean depths of sojourn and the degree of depth overlap allow the distinction of species subgroups: species preferring the uppermost shore (Coryphoblennius galerita, Aidablennius sphynx and Lipophrys trigloides), those mostly found in a middle stratum (Lipophrys canevai, Scartella cristata, Parablennius incognitus, Parablennius gattorugine) and two species with the lowest depth of sojourn (Parablennius pilicornis, Parablennius zvonimir). The relative depth position showed little seasonal variation and was similar at both Spanish and ltalian sites. The species of each subgroup which shows a high degree of spatial overlap is distinguished in other dimensions of its ecological niches, in particular by different feeding habits and differences in shelter characteristics. On the basis of exact depth distribution data the present study indicates that depth differences of Mediterranean blennies are very finely tuned and species-specific, even on a broad geographical and seasonal scale. Key words: Vertical zonation, Rocky shore, Ecological niches, Overlap, Microhabitat, Fish assemblag