The cultivated Manila clam, Ruditapes philippinarum, and the accidentally introduced Asian date mussel, Musculista senhousia, are nowadays the most abundant bivalve species in the Sacca di Goro (northeastern Italy). M. senhousia, with its sub-surficial extended mats, creates quite a heavy economical impact to clam shellfish culture. Individual Mediterranean shore crabs Carcinus aestuarii were allowed to forage on the 2 bivalve species to examine crab's preference in light of the optimal foraging theory. Crabs preferred M. senhousia over R. philippinarum: mortality was higher for the former (34.6%) than for the latter bivalve species (9.5%). It is suggested that the marked preference of C. aestuarii for Asian date mussels over Manila clams could be advantageously exploited to control or to reduce the extension of mats, especially where these create management problems to infaunal, burrowing bivalve cultures