Faunistic assemblages of a sublittoral coarse sand habitat of the northwestern Mediterranean

Abstract

SUMMARY:The sublittoral megabenthic assemblages of a northwestern Mediterranean coarse sandy beach exploited for the bivalve Callista chione were studied. The spatial and bathymetric variability of its distinctive faunal assemblages was characterised by quantitative sampling performed with a clam dredge. The taxa studied were Mollusca Bivalvia and Gastropoda, Crustacea Decapoda, Echinodermata and Pisces, which accounted for over 99% of the total biomass. Three welldifferentiated species assemblages were identified: (1) assemblage MSS (Medium Sand Shallow) in medium sand (D50=0.37 mm) and shallow waters (mean depth =6.5 m), (2) assemblage CSS (Coarse Sand Shallow) in coarse sand (D50=0.62 mm) in shallow waters (mean depth =6.7 m), and (3) assemblage CSD (Coarse Sand Deep) in coarse sand (D50=0.64 mm) in deeper waters (mean depth =16.2 m). Assemblage MSS was characterised by the codominance of the bivalves Mactra stultorum and Acanthocardia tuberculata. C. chione was dominant in both density and biomass in assemblages CSS and CSD. The occurrence of the crab Thia scutellata also characterised assemblage CSS, whereas the occurrence of the sea urchin Echinocardium mediterraneum characterised assemblage CSD. A depth breaking point of around 10 m determined the discontinuity between assemblages CSS and CSD, which was related to the closure depth of the beaches in the study area. Species richness was highest in the coarse sand communities; however, Shannon-Wiener diversity and Pielou equitability indexes were higher in the shallow fine sand community.Keywords: sublittoral, megabenthos, faunal assemblages, sediment characteristics, biodiversity, NW Mediterranean, coarse sand, Bivalvia, Crustacea. RESUMEN: Comunidades faunísticas de un hábitat sublitoral de arena gruesa en el Mediterráneo Noroccidental. -Se han estudiado las comunidades megabentónicas sublitorales de playas de arena gruesa afectadas por la pesquería del bivalvo Callista chione en el Mediterráneo noroccidental (Maresme). Se ha caracterizado la variabilidad espacial y batimétrica de las comunidades faunísticas presentes mediante un muestreo cuantitativo utilizando un rastrillo de bivalvos. Los taxones estudiados fueron Mollusca Bivalvia y Gastropoda, Crustacea Decapoda, Echinodermata y Pisces, los cuales representaron más del 99% de la biomasa total. Se identificaron tres comunidades bien diferenciadas: (1) comunidad MSS en arenas medias (D50=0.37 mm) y poco profundas (profundidad media =6.5 m), (2) comunidad CSS en arena gruesa (D50=0.62 mm) en aguas someras (6.7 m), y (3) comunidad CSD en arenas gruesas (D50=0.64 mm) en aguas más profundas (16.2 m). La comunidad MSS se caracterizó por la codominancia de los bivalvos Mactra stultorum y Acanthocardia tuberculata. C. chione dominó en densidad y biomasa en las comunidades CSS y CSD. La presencia del braquiuro Thia scutellata también caracterizó la comunidad CSS, mientras que la presencia del erizo Echinocardium mediterraneum caracterizó la comunidad CSD. Se detectó una discontinuidad entre las comunidades CSS...

Reproduction and size at first maturity in a Mediterranean exploited <em>Callista chione</em> bivalve bed

“…Baeta and Ramón (2013) reported that this bivalve was one of the main preys of the seastar species of the genus Astropecten in the western Mediterranean Sea, and they are also consumed by other invertebrates such as the gastropod Hexaplex trunculus (Morton et al 2007) and the cephalopod Octopus vulgaris (Fiorito and Gherardi 1999). C. chione is commercially exploited and consumed in Portugal and the Mediterranean Sea (Gaspar et al 2001, Tirado et al 2002, Metaxatos 2004, Pubill et al 2011, Baeta et al 2014 where it is captured with small boats using different types of artisanal dredges. One of the main coastal shellfish areas where a major clam fishery targeted the smooth clam is the Maresme coast, located to the northeast of Barcelona (NW Mediterranean Sea).…”