STRUCTURE AND EVOLUTION OF A DECAPOD CRUSTACEAN COMMUNITY FROM THE COASTAL DETRITIC BOTTOMS OF BARBATE (CADIZ, SOUTHERN SPAIN)

During 1993-1994 the decapod crustacean community of littoral detritic bottoms (15-24 m deep) from Southern Spain (Barbate Bay, near the Str aits of Gibraltar) were studied. The substrata include coarse sand, fi ne gravel, Amphioxus sand, and contain abundant bioclastic remains (bi valve and gastropod shells), which are under the influence of bottom c urrents. The taxocoenosis shows a clear dominance of the Anomura, 87% of those being hermit crabs; among them, Diogenes pugilator (Roux, 182 9) is the dominant species (76.6%). The structure and development of t he taxocoenosis during an annual cycle (number of specimens, richness, diversity, evenness and heterogeneity) is controlled by the cycle of D. pugilator, a characteristic species of shallow fine sand bottoms, a nd by the appearance of, or increase in, seaweed in the late summer an d autumn; this produces a notable seasonal variation and modifies the dominance and composition of species.