Habitat use by the pearly razorfish, Xyrichtys novacula (Pisces: Labridae)

The population density of the pearly razorfish, Xyrichtys novacula, was estimated in eastern Mediterranean areas and was related to specific environmental variables, laying emphasis on the sediment granulometry. The density of X. novacula ranged from 0 to 20.0 individuals per 1000 m(2). No correlation between X. novacula density and season, depth or the presence of common prey species was found. The X. novacula density was significantly correlated to the granulometry of the sediment, specifically to the median grain diameter Md phi and the quartile deviation QD phi, according to the model Density(1/4) = 1.626 - 0.354Md phi - 0.491QD phi. The highest X. novacula densities occur in moderately or well sorted, coarse or very coarse sand. The density and distribution of X. novacula seem to largely depend on the sediment characteristics, due to the sand-diving behaviour of the species that necessitates the existence of appropriate substrate. Evidence is presented against the reported theory that during the cold season the species spends most of the time buried in the sand.