Temporal variations in abundance and species composition of fish and epibenthic crustaceans of an intertidal zone: environmental factor influence
Fishes and epibenthic crustaceans were sampled for 1 year with a 1.5 m beam trawl in the intertidal zone of a sandy beach of the Eastern Channel. The intensity by which this intertidal zone is used by fishes and crustaceans was analyzed as well as the environmental factors influencing temporal variations in diversity, species abundance and assemblages. Between February 2005 and January 2006, 16 species were recorded. The presence of many juvenile indicated the important role played by the intertidal zone as a nursery ground. The brown shrimp Crangon crangon and O-group plaice Pleuronectes platessa are the two most abundant species of the intertidal ecosystem. Although the studied intertidal area is a multispecific nursery area, only six species had a major influence on the variation in total densities and can be considered as key species. Clear seasonal succession was observed in the species composition. The main structuring variables determining the occurrence and abundance of most of the species are water temperature, turbidity and dissolved oxygen. For some species, peak densities were observed during spring tides, suggesting selective tidal transport. Extreme winter conditions and subsequent migration of organisms to deeper water caused a decline in winter in both density and diversity.