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We analyze the bathymetric trends of demersal deep-sea flshes in the Catalan Sea ( N W Medlterranean) between 1000 and 2250 m depth In the first part of the study, only the pattern shown by the whole fauna ( wthin-fauna pattern ) 1s considered At 1200 m there is a significant decrease In fish mean welght, as a consequence of the replacement of the dominant large or medium-sized specles by small ones This fauna1 shift may be a consequence of the lower trophic availability at greater depths, as shown by an important decrease in megafaunal biomass between 1000 and 2250 m In the second part, the study focuses on the depth-size trends of the most common species ( within-species pattern ) Results show that the bigger-deeper phenomenon is not a well-estabhshed tendency None of the lower slope species and only 2 of the 5 middle slope species analyzed behave as bigger-deeper species Moreover some specles which display a bigger-deeper trend in North Atlantic waters do not show any significant trend In the Medlterranean Considering the recent Atlantic origin of Mediterranean ichthyofauna and the contrasting behaviour in the 2 areas, the hypothesis that mean slze increase with depth is the result of inhented ontogenic behaviour can be discarded

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