Crab predation on scallop (Pecten maximus) and its implication for scallop cultivation

Abstract

The feeding successes of four species of crabs (Crustacea: Brachyura) which are potential predators of the scallop Pecten maximus (L.) were studied under laboratory conditions. When provided with scallops of 4 and 5 cm shell height, Liocarcinus depurator (L.) did not consume any scallops whereas Liocarcinus puber (L.), Carcinus maenas (L.) and Cancer pagurus L. ate both size groupings but with varying success. The differences in the number of scallops eaten paralleled crab size such that C. pagurus, the species with the largest individuals (ca. 10.4 cm carapace width), ate the most, and small crabs (< 5.5 cm carapace width), irrespective of species, ate none or very few scallops. Further experiments with C. pagurus and a wider size range of scallops (3–9 cm shell height) revealed the following trends: as prey size increased, the proportion of crabs feeding decreased and there was minimal predation on scallops > 7 cm shell height; male and female crabs showed similar predatory behaviour; and marine fouling on scallop shells had no significant effect on crab feeding (X2 test, P > 0.05). These findings are discussed in relation to the potential for bottom culture of P. maximus.