Abstract
Community structure and faunal composition of decapod crustaceans off the west coast of central Italy (western Mediterranean) were investigated. Samples were collected during five trawl surveys carried out from June 1996 to June 2000 from 16 to 750 m depth. Multivariate analysis revealed the occurrence of five faunistic assemblages: 1) a strictly coastal community over sandy bottoms at depths Leptometra phalangium facies is found in many areas at depths between 120 and 180 m. The brachyuran crab Liocarcinus depurator dominates the shallow muddy-sandy bottoms of the shelf, while Parapenaeus longirostris is the most abundant species from the shelf to the upper slope assemblage. The dominant species on the middle slope are mainly nektobenthic ( Aristeus antennatus , Aristaeomorpha foliacea , Plesionika martia ), bentho-pelagic ( Pasiphaea sivado ) and benthic species ( Nephrops norvegicus ). The average diversity of the five assemblages defined increased with depth and the highest diversity values were found in the slope assemblages. Depth is the main factor influencing decapod assemblage composition, but sediment type and dissolved organic matter seem to be secondary structuring factors particularly in the shelf zone.
Highlights
Decapod crustaceans are a dominant or subdominant faunal component in temperate to subtropical assemblages, such as the Mediterranean Sea, and constitute a key taxon linking lower and higher trophic levels (Wenner and Boesch, 1979; Fariña et al, 1997; Cartes, 1998)
Multivariate analysis revealed the occurrence of five faunistic assemblages: 1) a strictly coastal community over sandy bottoms at depths
The existence of a shelfslope edge transition is a characteristic of the western and central Mediterranean where a Leptometra phalangium facies is found in many areas at depths between 120 and 180 m
Summary
Decapod crustaceans are a dominant or subdominant faunal component in temperate to subtropical assemblages, such as the Mediterranean Sea, and constitute a key taxon linking lower and higher trophic levels (Wenner and Boesch, 1979; Fariña et al, 1997; Cartes, 1998). In the Mediterranean, they are one of the dominant groups of megabenthic invertebrates on the continental shelf and slope and a very important fraction of demersal communities (Abelló et al, 1988; Maynou and Cartes, 2000; Colloca et al, 2003). The distribution and abundance of decapod crustacean species have been investigated in detail in the north-west basin (Abelló et al, 1988; Cartes and Sardà, 1993; Maynou and Cartes, 2000), on the continental slope (Cartes, 1993; Cartes et al, 1994; Sardà et al, 1994). Studies on demersal assemblage distribution in this area demonstrated the importance of several crustacean species (Biagi et al, 2002; Colloca et al, 2003) due to their abundance. The factors that may affect species distribution are discussed
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