Zonation of deep-sea decapod fauna in the Catalan Sea (Western Mediterranean)

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Zonation of deep-sea decapod crustacean fauna was established in the Catalan Sea (Western Mediterranean) based on a total of 66 bottom trawls carried out between 552 and 2261 m depth. An OTSB-14 bottom trawl was used as sampling gear. The main boundaries were located at 1200 to 1300 m and around 1900 to 2000 m. The 1200 to 1300 m boundary separates the decapod communities dwelling on the middle and lower slopes. The most important causes of decapod zonation in the Mediterranean are more closely linked to trophic factors, in view of the fact that basic hydrographic parameters (temperature, salinity) remain constant along the entire slope. In the Catalan Sea impoverishment of the organic matter content in the bottom sediment with depth and resuspension associated with the steeper portions of the slope (i.e. submarine canyons) are probably the most important factors responsible for the changes recorded. These factors may be directly responsible for the near absence of a variety of organisms that are highly abundant components of the endofauna on the middle slope but disappear below 1200 m. The limits of influence of different macroplanktonic groups (euphausiids, mesopelagic fishes) in the diet of benthic decapods also coincided with the observed boundaries between decapod communities.