Cymbium spp. (Gastropoda: Mollusca) as bivalve predators at the tidal flats of the Banc d'Arguin, Mauritania

Two species of the genus of large gastropods Cymbium were observed on the tidal flats of the Banc d'Arguin, Mauritania: C. pepo and C. tritonis . Average densities on a flat studied in detail were 0·0009 and 0·0014 individuals per m 2 , respectively. Both species leave the tidal flats in April and are absent until at least September. Their density on the tidal flats was maximal on sandy sediments. Probably the distribution of their prey species determines the distribution of Cymbium. Prey species observed were the bivalves Anadara senilis (97%), and an occasional Solen vagina and Venerupis sp. The annual predation pressure of Cymbium on intertidal Anadara was estimated to be <1%.